package db

import (
	"context"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"time"

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

func Connect(ctx context.Context, databaseURL string) (*pgxpool.Pool, error) {
	cfg, err := pgxpool.ParseConfig(databaseURL)
	if err != nil {
		return nil, fmt.Errorf("parse database url: %w", err)
	}
	cfg.MaxConns = 20
	cfg.MinConns = 2
	cfg.MaxConnLifetime = time.Hour
	cfg.MaxConnIdleTime = 15 * time.Minute
	cfg.HealthCheckPeriod = time.Minute

	pool, err := pgxpool.NewWithConfig(ctx, cfg)
	if err != nil {
		return nil, fmt.Errorf("connect: %w", err)
	}
	pingCtx, cancel := context.WithTimeout(ctx, 10*time.Second)
	defer cancel()
	if err := pool.Ping(pingCtx); err != nil {
		pool.Close()
		return nil, fmt.Errorf("ping: %w", err)
	}
	return pool, nil
}

func Migrate(ctx context.Context, pool *pgxpool.Pool, dir string) error {
	entries, err := os.ReadDir(dir)
	if err != nil {
		return fmt.Errorf("read migrations: %w", err)
	}
	var files []string
	for _, e := range entries {
		if e.IsDir() || !strings.HasSuffix(e.Name(), ".sql") {
			continue
		}
		files = append(files, e.Name())
	}
	sort.Strings(files)

	_, err = pool.Exec(ctx, `
		CREATE TABLE IF NOT EXISTS schema_migrations (
			filename TEXT PRIMARY KEY,
			applied_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
		)`)
	if err != nil {
		return err
	}

	for _, name := range files {
		var exists bool
		if err := pool.QueryRow(ctx, `SELECT EXISTS(SELECT 1 FROM schema_migrations WHERE filename=$1)`, name).Scan(&exists); err != nil {
			return err
		}
		if exists {
			continue
		}
		body, err := os.ReadFile(filepath.Join(dir, name))
		if err != nil {
			return err
		}
		tx, err := 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 (filename) VALUES ($1)`, name); err != nil {
			_ = tx.Rollback(ctx)
			return err
		}
		if err := tx.Commit(ctx); err != nil {
			return err
		}
	}
	return nil
}