// migrate — standalone CLI that applies tenant-registry's SQL migrations.
//
// Usage:
//
//	migrate up                     apply all pending migrations
//	migrate down                   roll back the most recent migration
//	migrate down --all             roll back every migration (DESTRUCTIVE)
//	migrate version                print the current schema version
//	migrate force <version>        mark a specific version applied (recovery)
//
// Reads DATABASE_URL from the environment. Migrations are embedded so this
// binary is self-contained — ship it as an Orca init container in prod.
package main

import (
	"context"
	"errors"
	"flag"
	"fmt"
	"log/slog"
	"os"

	"github.com/golang-migrate/migrate/v4"
	_ "github.com/golang-migrate/migrate/v4/database/postgres"
	"github.com/golang-migrate/migrate/v4/source/iofs"

	"gitea.meghsakha.com/platform/tenant-registry/migrations"
)

func main() {
	logger := slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: slog.LevelInfo}))
	slog.SetDefault(logger)

	allDown := flag.Bool("all", false, "with 'down', roll back every migration")
	flag.Usage = func() {
		fmt.Fprintf(os.Stderr, "usage: %s <up|down|version|force <n>>\n", os.Args[0])
		flag.PrintDefaults()
	}
	flag.Parse()

	args := flag.Args()
	if len(args) < 1 {
		flag.Usage()
		os.Exit(2)
	}

	dbURL := os.Getenv("DATABASE_URL")
	if dbURL == "" {
		slog.Error("DATABASE_URL not set")
		os.Exit(1)
	}

	if err := run(context.Background(), args, dbURL, *allDown); err != nil {
		slog.Error("migrate failed", "err", err)
		os.Exit(1)
	}
}

func run(ctx context.Context, args []string, dbURL string, allDown bool) error {
	src, err := iofs.New(migrations.FS, ".")
	if err != nil {
		return fmt.Errorf("load embedded migrations: %w", err)
	}

	m, err := migrate.NewWithSourceInstance("iofs", src, dbURL)
	if err != nil {
		return fmt.Errorf("open migrate: %w", err)
	}
	defer func() {
		if srcErr, dbErr := m.Close(); srcErr != nil || dbErr != nil {
			slog.Warn("close error", "src_err", srcErr, "db_err", dbErr)
		}
	}()

	cmd := args[0]
	switch cmd {
	case "up":
		err = m.Up()
		if errors.Is(err, migrate.ErrNoChange) {
			slog.Info("no pending migrations")
			return nil
		}
		if err != nil {
			return fmt.Errorf("up: %w", err)
		}
		v, dirty, _ := m.Version()
		slog.Info("migrate up complete", "version", v, "dirty", dirty)
		return nil

	case "down":
		if allDown {
			if err := m.Down(); err != nil && !errors.Is(err, migrate.ErrNoChange) {
				return fmt.Errorf("down all: %w", err)
			}
			slog.Info("migrate down --all complete (schema empty)")
			return nil
		}
		if err := m.Steps(-1); err != nil {
			if errors.Is(err, migrate.ErrNoChange) {
				slog.Info("no migrations to roll back")
				return nil
			}
			return fmt.Errorf("down 1: %w", err)
		}
		v, dirty, _ := m.Version()
		slog.Info("migrate down 1 complete", "version", v, "dirty", dirty)
		return nil

	case "version":
		v, dirty, err := m.Version()
		if errors.Is(err, migrate.ErrNilVersion) {
			slog.Info("no migrations applied")
			return nil
		}
		if err != nil {
			return fmt.Errorf("version: %w", err)
		}
		slog.Info("schema version", "version", v, "dirty", dirty)
		return nil

	case "force":
		if len(args) != 2 {
			return errors.New("usage: migrate force <version>")
		}
		var n int
		if _, err := fmt.Sscanf(args[1], "%d", &n); err != nil {
			return fmt.Errorf("invalid version %q", args[1])
		}
		if err := m.Force(n); err != nil {
			return fmt.Errorf("force: %w", err)
		}
		slog.Info("forced version", "version", n)
		return nil

	default:
		return fmt.Errorf("unknown command %q", cmd)
	}
}