// Command postgis-srid-migrate performs the explicitly approved EPSG:4326 metadata migration.
package main

import (
	"context"
	"encoding/json"
	"flag"
	"fmt"
	"log"
	"os"
	"os/signal"
	"strings"
	"syscall"
	"time"

	"fire-safety-ymd/internal/migration"

	"github.com/jackc/pgx/v5"
)

const (
	migrationDSNEnv = "FIRE_SAFETY_POSTGIS_MIGRATION_DSN"
	runtimeDSNEnv   = "FIRE_SAFETY_POSTGIS_DSN"
	commandTimeout  = 3 * time.Minute
)

func main() {
	apply := flag.Bool("apply", false, "commit the reviewed SRID metadata migration")
	confirmation := flag.String("confirm-source-crs", "", "required with --apply; must equal EPSG:4326")
	flag.Parse()

	dsn, err := selectDSN(*apply)
	if err != nil {
		log.Fatal(err)
	}
	connectionConfig, err := pgx.ParseConfig(dsn)
	if err != nil {
		log.Fatal("parse PostGIS migration configuration")
	}
	connectionConfig.RuntimeParams["application_name"] = "fire-safety-ymd-srid-migration"

	signalCtx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
	defer stop()
	ctx, cancel := context.WithTimeout(signalCtx, commandTimeout)
	defer cancel()

	conn, err := pgx.ConnectConfig(ctx, connectionConfig)
	if err != nil {
		log.Fatal("connect to PostGIS for SRID migration")
	}
	defer func() { _ = conn.Close(context.Background()) }()

	if !*apply {
		report, err := migration.Inspect(ctx, conn)
		if err != nil {
			log.Fatalf("inspect SRID migration state: %v", err)
		}
		writeJSON(report)
		if err := migration.ValidateForApply(report); err != nil {
			log.Fatalf("SRID migration preflight failed: %v", err)
		}
		fmt.Fprintln(os.Stderr, "preflight passed; no database changes were made")
		return
	}

	if *confirmation != "EPSG:4326" {
		log.Fatal("--apply requires --confirm-source-crs=EPSG:4326")
	}
	result, err := migration.ApplySRID4326(ctx, conn)
	if err != nil {
		log.Fatalf("apply SRID migration: %v", err)
	}
	writeJSON(result)
	fmt.Fprintln(os.Stderr, "SRID metadata migration committed")
}

func selectDSN(apply bool) (string, error) {
	migrationDSN := strings.TrimSpace(os.Getenv(migrationDSNEnv))
	if apply {
		if migrationDSN == "" {
			return "", fmt.Errorf("%s is required with --apply", migrationDSNEnv)
		}
		return migrationDSN, nil
	}
	if migrationDSN != "" {
		return migrationDSN, nil
	}
	runtimeDSN := strings.TrimSpace(os.Getenv(runtimeDSNEnv))
	if runtimeDSN == "" {
		return "", fmt.Errorf("%s or %s is required", migrationDSNEnv, runtimeDSNEnv)
	}
	return runtimeDSN, nil
}

func writeJSON(value any) {
	encoder := json.NewEncoder(os.Stdout)
	encoder.SetIndent("", "  ")
	if err := encoder.Encode(value); err != nil {
		log.Fatalf("encode migration report: %v", err)
	}
}