package db

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

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

type MigrationResult struct {
	Applied []string
	Skipped []string
}

func ApplyMigrations(ctx context.Context, pool *pgxpool.Pool, files map[string]string) (MigrationResult, error) {
	if _, err := pool.Exec(ctx, `CREATE TABLE IF NOT EXISTS schema_migrations (version text PRIMARY KEY, applied_at timestamptz NOT NULL DEFAULT now())`); err != nil {
		return MigrationResult{}, err
	}
	versions := make([]string, 0, len(files))
	for v := range files {
		versions = append(versions, v)
	}
	sort.Strings(versions)
	res := MigrationResult{}
	for _, version := range versions {
		var exists bool
		if err := pool.QueryRow(ctx, `SELECT EXISTS (SELECT 1 FROM schema_migrations WHERE version=$1)`, version).Scan(&exists); err != nil {
			return res, err
		}
		if exists {
			res.Skipped = append(res.Skipped, version)
			continue
		}
		tx, err := pool.Begin(ctx)
		if err != nil {
			return res, err
		}
		if _, err = tx.Exec(ctx, files[version]); err != nil {
			_ = tx.Rollback(ctx)
			return res, fmt.Errorf("apply migration %s: %w", version, err)
		}
		if _, err = tx.Exec(ctx, `INSERT INTO schema_migrations(version) VALUES($1)`, version); err != nil {
			_ = tx.Rollback(ctx)
			return res, err
		}
		if err = tx.Commit(ctx); err != nil {
			return res, err
		}
		res.Applied = append(res.Applied, version)
	}
	return res, nil
}

func LoadMigrationFiles(paths []string, read func(string) ([]byte, error)) (map[string]string, error) {
	out := map[string]string{}
	for _, p := range paths {
		b, err := read(p)
		if err != nil {
			return nil, err
		}
		name := filepath.Base(p)
		if !strings.HasSuffix(name, ".sql") {
			continue
		}
		out[name] = string(b)
	}
	return out, nil
}