package migrations

import (
	"context"
	"embed"
	"fmt"
	"io/fs"
	"sort"

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

//go:embed *.sql
var files embed.FS

func Apply(ctx context.Context, pool *pgxpool.Pool) error {
	conn, err := pool.Acquire(ctx)
	if err != nil {
		return fmt.Errorf("acquire migration connection: %w", err)
	}
	defer conn.Release()
	if _, err = conn.Exec(ctx, `SELECT pg_advisory_lock(hashtext('yovision-bell-migrations'))`); err != nil {
		return fmt.Errorf("lock migrations: %w", err)
	}
	defer func() {
		_, _ = conn.Exec(context.Background(), `SELECT pg_advisory_unlock(hashtext('yovision-bell-migrations'))`)
	}()
	if _, err := conn.Exec(ctx, `CREATE TABLE IF NOT EXISTS bell_schema_migrations (name text PRIMARY KEY, applied_at timestamptz NOT NULL DEFAULT now())`); err != nil {
		return fmt.Errorf("create migration ledger: %w", err)
	}
	entries, err := fs.ReadDir(files, ".")
	if err != nil {
		return fmt.Errorf("read embedded migrations: %w", err)
	}
	sort.Slice(entries, func(i, j int) bool { return entries[i].Name() < entries[j].Name() })
	for _, entry := range entries {
		if entry.IsDir() || len(entry.Name()) < 4 || entry.Name()[len(entry.Name())-4:] != ".sql" {
			continue
		}
		var applied bool
		if err := conn.QueryRow(ctx, `SELECT EXISTS(SELECT 1 FROM bell_schema_migrations WHERE name=$1)`, entry.Name()).Scan(&applied); err != nil {
			return err
		}
		if applied {
			continue
		}
		sqlBytes, err := files.ReadFile(entry.Name())
		if err != nil {
			return err
		}
		tx, err := conn.Begin(ctx)
		if err != nil {
			return err
		}
		if _, err = tx.Exec(ctx, string(sqlBytes)); err == nil {
			_, err = tx.Exec(ctx, `INSERT INTO bell_schema_migrations(name) VALUES($1)`, entry.Name())
		}
		if err != nil {
			_ = tx.Rollback(ctx)
			return fmt.Errorf("apply migration %s: %w", entry.Name(), err)
		}
		if err := tx.Commit(ctx); err != nil {
			return fmt.Errorf("commit migration %s: %w", entry.Name(), err)
		}
	}
	return nil
}