package storage

import (
	"context"
	"embed"
	"fmt"
	"log/slog"
	"sort"
	"strings"

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

//go:embed migrations/*.sql
var migrationFS embed.FS

type Storage struct {
	pool *pgxpool.Pool
}

func New(ctx context.Context, dsn string) (*Storage, error) {
	pool, err := pgxpool.New(ctx, dsn)
	if err != nil {
		return nil, fmt.Errorf("connect: %w", err)
	}
	if err := pool.Ping(ctx); err != nil {
		pool.Close()
		return nil, fmt.Errorf("ping: %w", err)
	}
	return &Storage{pool: pool}, nil
}

func (s *Storage) Close() { s.pool.Close() }

func (s *Storage) Pool() *pgxpool.Pool { return s.pool }

// Migrate применяет sql-файлы из migrations по порядку имён.
// Каждый файл выполняется в транзакции и отмечается в schema_migrations.
func (s *Storage) Migrate(ctx context.Context) error {
	_, err := s.pool.Exec(ctx, `
		CREATE TABLE IF NOT EXISTS schema_migrations (
			version    text PRIMARY KEY,
			applied_at timestamptz NOT NULL DEFAULT now()
		)`)
	if err != nil {
		return fmt.Errorf("create schema_migrations: %w", err)
	}

	applied := map[string]bool{}
	rows, err := s.pool.Query(ctx, `SELECT version FROM schema_migrations`)
	if err != nil {
		return fmt.Errorf("read applied: %w", err)
	}
	for rows.Next() {
		var v string
		if err := rows.Scan(&v); err != nil {
			rows.Close()
			return err
		}
		applied[v] = true
	}
	rows.Close()
	if err := rows.Err(); err != nil {
		return err
	}

	entries, err := migrationFS.ReadDir("migrations")
	if err != nil {
		return err
	}
	names := make([]string, 0, len(entries))
	for _, e := range entries {
		if !e.IsDir() && strings.HasSuffix(e.Name(), ".sql") {
			names = append(names, e.Name())
		}
	}
	sort.Strings(names)

	for _, name := range names {
		if applied[name] {
			continue
		}
		body, err := migrationFS.ReadFile("migrations/" + name)
		if err != nil {
			return err
		}
		tx, err := s.pool.Begin(ctx)
		if err != nil {
			return err
		}
		if _, err := tx.Exec(ctx, string(body)); err != nil {
			_ = tx.Rollback(ctx)
			return fmt.Errorf("migration %s: %w", name, err)
		}
		if _, err := tx.Exec(ctx, `INSERT INTO schema_migrations (version) VALUES ($1)`, name); err != nil {
			_ = tx.Rollback(ctx)
			return err
		}
		if err := tx.Commit(ctx); err != nil {
			return err
		}
		slog.Info("migration applied", "file", name)
	}
	return nil
}