778 lines
20 KiB
Go
778 lines
20 KiB
Go
package main
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import (
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"compress/gzip"
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"database/sql"
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"embed"
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"encoding/json"
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"fmt"
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"io"
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"io/fs"
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"log"
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"net/http"
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"os"
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"strconv"
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"strings"
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"sync"
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"time"
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_ "modernc.org/sqlite"
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)
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//go:embed static/*
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var staticFiles embed.FS
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const (
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geojsonURL = "https://regieessencequebec.ca/stations.geojson.gz"
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defaultPort = "8080"
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pollInterval = 5 * time.Minute
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)
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// GeoJSON structures matching the upstream format.
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type GeoJSONResponse struct {
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Type string `json:"type"`
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Metadata *GeoJSONMeta `json:"metadata,omitempty"`
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Features json.RawMessage `json:"features"`
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}
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type GeoJSONMeta struct {
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GeneratedAt string `json:"generated_at"`
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ExcelURL string `json:"excel_url"`
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TotalStations int `json:"total_stations"`
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ExcelSizeBytes int `json:"excel_size_bytes"`
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}
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// Station is our simplified JSON shape for the frontend.
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type Station struct {
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Name string `json:"name"`
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Brand string `json:"brand"`
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Address string `json:"address"`
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Region string `json:"region"`
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PostalCode string `json:"postalCode"`
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Lat float64 `json:"lat"`
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Lng float64 `json:"lng"`
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Regular float64 `json:"regular"`
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Super float64 `json:"super"`
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Diesel float64 `json:"diesel"`
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}
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type StationsResponse struct {
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LastUpdated string `json:"lastUpdated"`
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Stations []Station `json:"stations"`
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}
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// Snapshot holds the aggregated statistics for one fetch.
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type Snapshot struct {
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GeneratedAt string `json:"generatedAt"`
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FetchedAt string `json:"fetchedAt"`
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RegularAvg float64 `json:"regularAvg"`
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RegularMin float64 `json:"regularMin"`
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RegularMax float64 `json:"regularMax"`
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SuperAvg float64 `json:"superAvg"`
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DieselAvg float64 `json:"dieselAvg"`
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StationCount int `json:"stationCount"`
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}
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type StatsResponse struct {
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Snapshots []Snapshot `json:"snapshots"`
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}
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// In-memory cache
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var (
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cacheMu sync.RWMutex
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cachedResp *StationsResponse
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)
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var db *sql.DB
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func main() {
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port := os.Getenv("PORT")
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if port == "" {
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port = defaultPort
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}
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dbPath := os.Getenv("ESSENCE_DB")
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if dbPath == "" {
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dbPath = "./essence.db"
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}
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var err error
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db, err = initDB(dbPath)
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if err != nil {
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log.Fatalf("db init: %v", err)
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}
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defer db.Close()
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// Initial fetch, then background poll every 5 minutes.
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go poller()
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staticSub, err := fs.Sub(staticFiles, "static")
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if err != nil {
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log.Fatalf("static files: %v", err)
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}
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http.HandleFunc("/api/stations", handleStations)
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http.HandleFunc("/api/stats", handleStats)
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http.HandleFunc("/api/regions", handleRegions)
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http.HandleFunc("/api/stats/region", handleRegionStats)
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http.HandleFunc("/api/station-deltas", handleStationDeltas)
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http.Handle("/", http.FileServer(http.FS(staticSub)))
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log.Printf("Listening on http://localhost:%s", port)
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log.Fatal(http.ListenAndServe(":"+port, nil))
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}
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// initDB opens (or creates) the SQLite database and ensures the schema exists.
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func initDB(path string) (*sql.DB, error) {
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d, err := sql.Open("sqlite", path)
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if err != nil {
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return nil, err
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}
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_, err = d.Exec(`
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CREATE TABLE IF NOT EXISTS snapshots (
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generated_at TEXT PRIMARY KEY,
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fetched_at TEXT NOT NULL,
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regular_avg REAL,
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regular_min REAL,
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regular_max REAL,
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super_avg REAL,
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diesel_avg REAL,
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station_count INTEGER
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)
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`)
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if err != nil {
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return nil, fmt.Errorf("create table: %w", err)
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}
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_, err = d.Exec(`
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CREATE TABLE IF NOT EXISTS region_snapshots (
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generated_at TEXT NOT NULL,
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region TEXT NOT NULL,
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regular_avg REAL,
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regular_min REAL,
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regular_max REAL,
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super_avg REAL,
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diesel_avg REAL,
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station_count INTEGER,
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PRIMARY KEY (generated_at, region)
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)
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`)
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if err != nil {
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return nil, fmt.Errorf("create region_snapshots table: %w", err)
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}
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_, err = d.Exec(`
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CREATE TABLE IF NOT EXISTS station_prices (
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address TEXT NOT NULL,
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generated_at TEXT NOT NULL,
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regular REAL,
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super REAL,
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diesel REAL,
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PRIMARY KEY (address, generated_at)
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)
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`)
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if err != nil {
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return nil, fmt.Errorf("create station_prices table: %w", err)
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}
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// Keep only the last 48 hours of per-station price history to bound table size.
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_, err = d.Exec(`
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CREATE INDEX IF NOT EXISTS idx_station_prices_generated_at
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ON station_prices (generated_at)
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`)
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if err != nil {
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return nil, fmt.Errorf("create station_prices index: %w", err)
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}
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return d, nil
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}
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// poller fetches immediately then every pollInterval.
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func poller() {
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fetchAndStore()
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ticker := time.NewTicker(pollInterval)
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defer ticker.Stop()
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for range ticker.C {
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fetchAndStore()
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}
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}
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// fetchAndStore fetches upstream data, updates the in-memory cache, and
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// persists a snapshot to SQLite if the data has a new generated_at value.
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func fetchAndStore() {
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resp, err := fetchAndParse()
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if err != nil {
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log.Printf("fetch error: %v", err)
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return
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}
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cacheMu.Lock()
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cachedResp = resp
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cacheMu.Unlock()
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if resp.LastUpdated == "" {
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return
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}
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// Compute and persist global aggregate.
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snap := computeSnapshot(resp)
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_, err = db.Exec(`
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INSERT OR IGNORE INTO snapshots
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(generated_at, fetched_at, regular_avg, regular_min, regular_max, super_avg, diesel_avg, station_count)
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VALUES (?, ?, ?, ?, ?, ?, ?, ?)`,
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snap.GeneratedAt,
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snap.FetchedAt,
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snap.RegularAvg,
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snap.RegularMin,
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snap.RegularMax,
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snap.SuperAvg,
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snap.DieselAvg,
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snap.StationCount,
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)
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if err != nil {
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log.Printf("db insert error: %v", err)
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}
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// Compute and persist per-region aggregates.
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regionSnaps := computeRegionSnapshots(resp)
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for _, rs := range regionSnaps {
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_, err = db.Exec(`
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INSERT OR IGNORE INTO region_snapshots
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(generated_at, region, regular_avg, regular_min, regular_max, super_avg, diesel_avg, station_count)
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VALUES (?, ?, ?, ?, ?, ?, ?, ?)`,
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rs.GeneratedAt,
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rs.Region,
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rs.RegularAvg,
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rs.RegularMin,
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rs.RegularMax,
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rs.SuperAvg,
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rs.DieselAvg,
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rs.StationCount,
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)
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if err != nil {
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log.Printf("db region insert error: %v", err)
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}
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}
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// Persist per-station prices for 24h delta calculations.
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for _, s := range resp.Stations {
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_, err = db.Exec(`
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INSERT OR IGNORE INTO station_prices (address, generated_at, regular, super, diesel)
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VALUES (?, ?, ?, ?, ?)`,
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s.Address,
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resp.LastUpdated,
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s.Regular,
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s.Super,
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s.Diesel,
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)
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if err != nil {
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log.Printf("db station_prices insert error: %v", err)
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}
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}
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// Prune station_prices rows older than 48 hours.
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cutoff := time.Now().UTC().Add(-48 * time.Hour).Format(time.RFC3339)
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if _, err = db.Exec(`DELETE FROM station_prices WHERE generated_at < ?`, cutoff); err != nil {
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log.Printf("db station_prices prune error: %v", err)
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}
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}
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// computeSnapshot derives aggregate statistics from a StationsResponse.
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func computeSnapshot(resp *StationsResponse) Snapshot {
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now := time.Now().UTC().Format(time.RFC3339)
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snap := Snapshot{
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GeneratedAt: resp.LastUpdated,
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FetchedAt: now,
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}
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var regularSum, superSum, dieselSum float64
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var regularCount, superCount, dieselCount int
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snap.RegularMin = 1<<53 - 1
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snap.RegularMax = 0
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for _, s := range resp.Stations {
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if s.Regular > 0 {
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regularSum += s.Regular
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regularCount++
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if s.Regular < snap.RegularMin {
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snap.RegularMin = s.Regular
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}
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if s.Regular > snap.RegularMax {
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snap.RegularMax = s.Regular
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}
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}
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if s.Super > 0 {
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superSum += s.Super
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superCount++
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}
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if s.Diesel > 0 {
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dieselSum += s.Diesel
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dieselCount++
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}
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}
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snap.StationCount = len(resp.Stations)
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if regularCount > 0 {
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snap.RegularAvg = regularSum / float64(regularCount)
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} else {
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snap.RegularMin = 0
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}
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if superCount > 0 {
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snap.SuperAvg = superSum / float64(superCount)
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}
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if dieselCount > 0 {
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snap.DieselAvg = dieselSum / float64(dieselCount)
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}
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return snap
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}
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// RegionSnapshot holds aggregated statistics for one fetch scoped to a region.
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type RegionSnapshot struct {
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GeneratedAt string `json:"generatedAt"`
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Region string `json:"region"`
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RegularAvg float64 `json:"regularAvg"`
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RegularMin float64 `json:"regularMin"`
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RegularMax float64 `json:"regularMax"`
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SuperAvg float64 `json:"superAvg"`
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DieselAvg float64 `json:"dieselAvg"`
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StationCount int `json:"stationCount"`
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}
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// computeRegionSnapshots derives per-region aggregate statistics from a StationsResponse.
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func computeRegionSnapshots(resp *StationsResponse) []RegionSnapshot {
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type acc struct {
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regularSum, superSum, dieselSum float64
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regularCount, superCount, dieselCount int
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regularMin, regularMax float64
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stationCount int
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}
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byRegion := map[string]*acc{}
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for _, s := range resp.Stations {
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if s.Region == "" {
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continue
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}
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a, ok := byRegion[s.Region]
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if !ok {
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a = &acc{regularMin: 1<<53 - 1}
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byRegion[s.Region] = a
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}
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a.stationCount++
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if s.Regular > 0 {
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a.regularSum += s.Regular
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a.regularCount++
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if s.Regular < a.regularMin {
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a.regularMin = s.Regular
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}
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if s.Regular > a.regularMax {
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a.regularMax = s.Regular
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}
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}
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if s.Super > 0 {
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a.superSum += s.Super
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a.superCount++
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}
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if s.Diesel > 0 {
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a.dieselSum += s.Diesel
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a.dieselCount++
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}
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}
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snaps := make([]RegionSnapshot, 0, len(byRegion))
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for region, a := range byRegion {
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rs := RegionSnapshot{
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GeneratedAt: resp.LastUpdated,
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Region: region,
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StationCount: a.stationCount,
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}
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if a.regularCount > 0 {
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rs.RegularAvg = a.regularSum / float64(a.regularCount)
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rs.RegularMin = a.regularMin
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rs.RegularMax = a.regularMax
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}
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if a.superCount > 0 {
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rs.SuperAvg = a.superSum / float64(a.superCount)
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}
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if a.dieselCount > 0 {
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rs.DieselAvg = a.dieselSum / float64(a.dieselCount)
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}
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snaps = append(snaps, rs)
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}
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return snaps
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}
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func handleStations(w http.ResponseWriter, r *http.Request) {
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cacheMu.RLock()
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resp := cachedResp
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cacheMu.RUnlock()
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if resp == nil {
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http.Error(w, "data not yet available, please retry shortly", http.StatusServiceUnavailable)
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return
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}
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w.Header().Set("Content-Type", "application/json")
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w.Header().Set("Cache-Control", "public, max-age=300")
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json.NewEncoder(w).Encode(resp)
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}
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func handleStats(w http.ResponseWriter, r *http.Request) {
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daysStr := r.URL.Query().Get("days")
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days := 7
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if daysStr != "" {
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if d, err := strconv.Atoi(daysStr); err == nil && d > 0 {
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days = d
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}
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}
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// days=0 means all data
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var rows *sql.Rows
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var err error
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if daysStr == "0" {
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rows, err = db.Query(`
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SELECT generated_at, fetched_at, regular_avg, regular_min, regular_max,
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super_avg, diesel_avg, station_count
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FROM snapshots
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ORDER BY generated_at ASC
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`)
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} else {
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since := time.Now().UTC().Add(-time.Duration(days) * 24 * time.Hour).Format(time.RFC3339)
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rows, err = db.Query(`
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SELECT generated_at, fetched_at, regular_avg, regular_min, regular_max,
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super_avg, diesel_avg, station_count
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FROM snapshots
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WHERE generated_at >= ?
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ORDER BY generated_at ASC
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`, since)
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}
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if err != nil {
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http.Error(w, fmt.Sprintf("db query: %v", err), http.StatusInternalServerError)
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return
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}
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defer rows.Close()
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snapshots := []Snapshot{}
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for rows.Next() {
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var s Snapshot
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if err := rows.Scan(&s.GeneratedAt, &s.FetchedAt, &s.RegularAvg, &s.RegularMin, &s.RegularMax,
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&s.SuperAvg, &s.DieselAvg, &s.StationCount); err != nil {
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http.Error(w, fmt.Sprintf("db scan: %v", err), http.StatusInternalServerError)
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return
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}
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snapshots = append(snapshots, s)
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}
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w.Header().Set("Content-Type", "application/json")
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json.NewEncoder(w).Encode(StatsResponse{Snapshots: snapshots})
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}
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// handleRegions returns a sorted list of distinct region names from region_snapshots.
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func handleRegions(w http.ResponseWriter, r *http.Request) {
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rows, err := db.Query(`SELECT DISTINCT region FROM region_snapshots ORDER BY region ASC`)
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if err != nil {
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http.Error(w, fmt.Sprintf("db query: %v", err), http.StatusInternalServerError)
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return
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}
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defer rows.Close()
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regions := []string{}
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for rows.Next() {
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var region string
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if err := rows.Scan(®ion); err != nil {
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http.Error(w, fmt.Sprintf("db scan: %v", err), http.StatusInternalServerError)
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return
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}
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regions = append(regions, region)
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}
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w.Header().Set("Content-Type", "application/json")
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json.NewEncoder(w).Encode(regions)
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}
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// handleRegionStats returns time-series snapshots for a specific region.
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func handleRegionStats(w http.ResponseWriter, r *http.Request) {
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region := r.URL.Query().Get("region")
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if region == "" {
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http.Error(w, "missing region parameter", http.StatusBadRequest)
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return
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}
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daysStr := r.URL.Query().Get("days")
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days := 7
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if daysStr != "" {
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if d, err := strconv.Atoi(daysStr); err == nil && d > 0 {
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days = d
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}
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}
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var rows *sql.Rows
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var err error
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if daysStr == "0" {
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rows, err = db.Query(`
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SELECT generated_at, regular_avg, regular_min, regular_max,
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super_avg, diesel_avg, station_count
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FROM region_snapshots
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WHERE region = ?
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ORDER BY generated_at ASC
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`, region)
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} else {
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since := time.Now().UTC().Add(-time.Duration(days) * 24 * time.Hour).Format(time.RFC3339)
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rows, err = db.Query(`
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SELECT generated_at, regular_avg, regular_min, regular_max,
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super_avg, diesel_avg, station_count
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FROM region_snapshots
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WHERE region = ? AND generated_at >= ?
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ORDER BY generated_at ASC
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`, region, since)
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}
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if err != nil {
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http.Error(w, fmt.Sprintf("db query: %v", err), http.StatusInternalServerError)
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return
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}
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defer rows.Close()
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snapshots := []Snapshot{}
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for rows.Next() {
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var s Snapshot
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if err := rows.Scan(&s.GeneratedAt, &s.RegularAvg, &s.RegularMin, &s.RegularMax,
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&s.SuperAvg, &s.DieselAvg, &s.StationCount); err != nil {
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http.Error(w, fmt.Sprintf("db scan: %v", err), http.StatusInternalServerError)
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return
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}
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snapshots = append(snapshots, s)
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}
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w.Header().Set("Content-Type", "application/json")
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json.NewEncoder(w).Encode(StatsResponse{Snapshots: snapshots})
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}
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|
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// StationDelta holds the price change percentage for a station over the available
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|
// history window. Fields are pointers so that missing data serialises as JSON null.
|
|
// ElapsedHours is the actual time span between the oldest and newest snapshot used.
|
|
type StationDelta struct {
|
|
Regular *float64 `json:"regular"`
|
|
Super *float64 `json:"super"`
|
|
Diesel *float64 `json:"diesel"`
|
|
ElapsedHours float64 `json:"elapsedHours"`
|
|
}
|
|
|
|
// handleStationDeltas returns a map of address → StationDelta for all stations
|
|
// that have at least two distinct price records within the 48h retention window.
|
|
// The delta is computed between the oldest and newest available snapshot, and
|
|
// ElapsedHours carries the actual time span so the frontend can label it honestly.
|
|
func handleStationDeltas(w http.ResponseWriter, r *http.Request) {
|
|
since := time.Now().UTC().Add(-48 * time.Hour).Format(time.RFC3339)
|
|
|
|
// Fetch all rows in the retention window, oldest first.
|
|
rows, err := db.Query(`
|
|
SELECT address, generated_at, regular, super, diesel
|
|
FROM station_prices
|
|
WHERE generated_at >= ?
|
|
ORDER BY address ASC, generated_at ASC
|
|
`, since)
|
|
if err != nil {
|
|
http.Error(w, fmt.Sprintf("db query: %v", err), http.StatusInternalServerError)
|
|
return
|
|
}
|
|
defer rows.Close()
|
|
|
|
type priceRow struct {
|
|
generatedAt string
|
|
regular float64
|
|
super float64
|
|
diesel float64
|
|
}
|
|
|
|
type addrRows struct {
|
|
old *priceRow // first (oldest) row seen for this address
|
|
cur *priceRow // last (newest) row seen for this address
|
|
}
|
|
byAddr := map[string]*addrRows{}
|
|
|
|
for rows.Next() {
|
|
var addr, genAt string
|
|
var reg, sup, die float64
|
|
if err := rows.Scan(&addr, &genAt, ®, &sup, &die); err != nil {
|
|
http.Error(w, fmt.Sprintf("db scan: %v", err), http.StatusInternalServerError)
|
|
return
|
|
}
|
|
ar, ok := byAddr[addr]
|
|
if !ok {
|
|
ar = &addrRows{}
|
|
byAddr[addr] = ar
|
|
}
|
|
row := &priceRow{generatedAt: genAt, regular: reg, super: sup, diesel: die}
|
|
// First row seen becomes the baseline; every row updates current.
|
|
if ar.old == nil {
|
|
ar.old = row
|
|
}
|
|
ar.cur = row
|
|
}
|
|
|
|
pctChange := func(cur, old float64) *float64 {
|
|
if old <= 0 || cur <= 0 {
|
|
return nil
|
|
}
|
|
v := (cur - old) / old * 100
|
|
return &v
|
|
}
|
|
|
|
result := make(map[string]StationDelta, len(byAddr))
|
|
for addr, ar := range byAddr {
|
|
// Need at least two distinct snapshots to compute a meaningful delta.
|
|
if ar.old == nil || ar.cur == nil || ar.old.generatedAt == ar.cur.generatedAt {
|
|
continue
|
|
}
|
|
oldT, err1 := time.Parse(time.RFC3339, ar.old.generatedAt)
|
|
curT, err2 := time.Parse(time.RFC3339, ar.cur.generatedAt)
|
|
if err1 != nil || err2 != nil {
|
|
continue
|
|
}
|
|
result[addr] = StationDelta{
|
|
Regular: pctChange(ar.cur.regular, ar.old.regular),
|
|
Super: pctChange(ar.cur.super, ar.old.super),
|
|
Diesel: pctChange(ar.cur.diesel, ar.old.diesel),
|
|
ElapsedHours: curT.Sub(oldT).Hours(),
|
|
}
|
|
}
|
|
|
|
w.Header().Set("Content-Type", "application/json")
|
|
w.Header().Set("Cache-Control", "public, max-age=300")
|
|
json.NewEncoder(w).Encode(result)
|
|
}
|
|
|
|
func fetchAndParse() (*StationsResponse, error) {
|
|
log.Println("Fetching GeoJSON data from upstream...")
|
|
|
|
req, err := http.NewRequest("GET", geojsonURL, nil)
|
|
if err != nil {
|
|
return nil, fmt.Errorf("creating request: %w", err)
|
|
}
|
|
req.Header.Set("Accept-Encoding", "gzip")
|
|
req.Header.Set("User-Agent", "essence-quebec-map/1.0")
|
|
|
|
client := &http.Client{Timeout: 30 * time.Second}
|
|
resp, err := client.Do(req)
|
|
if err != nil {
|
|
return nil, fmt.Errorf("fetching data: %w", err)
|
|
}
|
|
defer resp.Body.Close()
|
|
|
|
if resp.StatusCode != http.StatusOK {
|
|
return nil, fmt.Errorf("unexpected status: %d", resp.StatusCode)
|
|
}
|
|
|
|
// Handle gzip if the response is compressed
|
|
var reader io.Reader = resp.Body
|
|
if resp.Header.Get("Content-Encoding") == "gzip" || strings.HasSuffix(geojsonURL, ".gz") {
|
|
gz, err := gzip.NewReader(resp.Body)
|
|
if err != nil {
|
|
return nil, fmt.Errorf("gzip reader: %w", err)
|
|
}
|
|
defer gz.Close()
|
|
reader = gz
|
|
}
|
|
|
|
var geojson GeoJSONResponse
|
|
if err := json.NewDecoder(reader).Decode(&geojson); err != nil {
|
|
return nil, fmt.Errorf("decoding geojson: %w", err)
|
|
}
|
|
|
|
// Parse features
|
|
var features []struct {
|
|
Geometry struct {
|
|
Coordinates [2]float64 `json:"coordinates"`
|
|
} `json:"geometry"`
|
|
Properties struct {
|
|
Name string `json:"Name"`
|
|
Brand string `json:"brand"`
|
|
Address string `json:"Address"`
|
|
PostalCode string `json:"PostalCode"`
|
|
Region string `json:"Region"`
|
|
Prices []struct {
|
|
GasType string `json:"GasType"`
|
|
Price *string `json:"Price"`
|
|
IsAvailable bool `json:"IsAvailable"`
|
|
} `json:"Prices"`
|
|
} `json:"properties"`
|
|
}
|
|
|
|
if err := json.Unmarshal(geojson.Features, &features); err != nil {
|
|
return nil, fmt.Errorf("parsing features: %w", err)
|
|
}
|
|
|
|
var stations []Station
|
|
for _, f := range features {
|
|
lng := f.Geometry.Coordinates[0]
|
|
lat := f.Geometry.Coordinates[1]
|
|
if lat == 0 && lng == 0 {
|
|
continue
|
|
}
|
|
|
|
s := Station{
|
|
Name: f.Properties.Name,
|
|
Brand: f.Properties.Brand,
|
|
Address: f.Properties.Address,
|
|
Region: f.Properties.Region,
|
|
PostalCode: f.Properties.PostalCode,
|
|
Lat: lat,
|
|
Lng: lng,
|
|
}
|
|
|
|
for _, p := range f.Properties.Prices {
|
|
if p.Price == nil || !p.IsAvailable {
|
|
continue
|
|
}
|
|
price := parsePrice(*p.Price)
|
|
if price <= 0 {
|
|
continue
|
|
}
|
|
switch p.GasType {
|
|
case "Régulier":
|
|
s.Regular = price
|
|
case "Super":
|
|
s.Super = price
|
|
case "Diesel":
|
|
s.Diesel = price
|
|
}
|
|
}
|
|
|
|
if s.Regular <= 0 {
|
|
continue
|
|
}
|
|
|
|
stations = append(stations, s)
|
|
}
|
|
|
|
lastUpdated := ""
|
|
if geojson.Metadata != nil && geojson.Metadata.GeneratedAt != "" {
|
|
lastUpdated = geojson.Metadata.GeneratedAt
|
|
}
|
|
|
|
log.Printf("Parsed %d stations (last updated: %s)", len(stations), lastUpdated)
|
|
|
|
return &StationsResponse{
|
|
LastUpdated: lastUpdated,
|
|
Stations: stations,
|
|
}, nil
|
|
}
|
|
|
|
// parsePrice converts "190.9¢" to 190.9
|
|
func parsePrice(s string) float64 {
|
|
s = strings.TrimSpace(s)
|
|
if s == "" || s == "N/D" {
|
|
return 0
|
|
}
|
|
s = strings.TrimSuffix(s, "¢")
|
|
s = strings.TrimSuffix(s, "\u00a2") // cent sign
|
|
|
|
var v float64
|
|
_, err := fmt.Sscanf(s, "%f", &v)
|
|
if err != nil {
|
|
return 0
|
|
}
|
|
return v
|
|
}
|