package db

import (
	"context"
	"database/sql"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"

	"github.com/jackc/pgx/v5/pgxpool"
	"github.com/jackc/pgx/v5/stdlib"
	"github.com/pressly/goose/v3"
)

const schemaTable = "goose_db_version"

// RunMigrations 执行 goose 迁移链。
func RunMigrations(ctx context.Context, pool *pgxpool.Pool, migrationsDir string) error {
	if pool == nil {
		return fmt.Errorf("db migrate: pool required")
	}
	absDir, err := filepath.Abs(migrationsDir)
	if err != nil {
		return err
	}
	if _, err := os.Stat(absDir); err != nil {
		return fmt.Errorf("db migrate: directory %s: %w", absDir, err)
	}

	db := stdlib.OpenDB(*pool.Config().ConnConfig)
	defer db.Close()

	if err := goose.SetDialect("postgres"); err != nil {
		return err
	}
	goose.SetTableName(schemaTable)

	if err := goose.UpContext(ctx, db, absDir); err != nil {
		return fmt.Errorf("db migrate up: %w", err)
	}
	return nil
}

// CurrentVersion 返回当前 schema 版本号。
func CurrentVersion(ctx context.Context, pool *pgxpool.Pool) (int64, error) {
	if pool == nil {
		return 0, fmt.Errorf("db migrate: pool required")
	}
	var version int64
	err := pool.QueryRow(ctx, fmt.Sprintf(`
		SELECT COALESCE(MAX(version_id), 0)::bigint FROM %s
	`, schemaTable)).Scan(&version)
	if err != nil {
		// 表不存在时视为未迁移
		if strings.Contains(err.Error(), "does not exist") {
			return 0, nil
		}
		return 0, err
	}
	return version, nil
}

// ExpectedMigrationCount 统计 migrations 目录下 .sql 文件数量。
func ExpectedMigrationCount(migrationsDir string) (int, error) {
	entries, err := os.ReadDir(migrationsDir)
	if err != nil {
		return 0, err
	}
	count := 0
	for _, e := range entries {
		if !e.IsDir() && strings.HasSuffix(e.Name(), ".sql") {
			count++
		}
	}
	return count, nil
}

// ResolveMigrationsDir 定位 goose 迁移目录。
func ResolveMigrationsDir() string {
	candidates := []string{
		"deploy/postgres/goose",
		"../deploy/postgres/goose",
		"../../deploy/postgres/goose",
	}
	for _, c := range candidates {
		if fi, err := os.Stat(c); err == nil && fi.IsDir() {
			return c
		}
	}
	return "deploy/postgres/goose"
}

// OpenSQLDB 从 pgx pool 打开 database/sql（测试辅助）。
func OpenSQLDB(pool *pgxpool.Pool) *sql.DB {
	return stdlib.OpenDB(*pool.Config().ConnConfig)
}

// ListMigrationFiles 按名称排序列出迁移文件（测试辅助）。
func ListMigrationFiles(dir string) ([]string, error) {
	entries, err := os.ReadDir(dir)
	if err != nil {
		return nil, err
	}
	var files []string
	for _, e := range entries {
		if !e.IsDir() && strings.HasSuffix(e.Name(), ".sql") {
			files = append(files, e.Name())
		}
	}
	sort.Strings(files)
	return files, nil
}