package db

import (
	"context"
	"database/sql"
	"fmt"
	"os"
	"strings"

	_ "modernc.org/sqlite"
)

// openSQLite 打开 SQLite 库文件;文件不存在时报错而非静默建空库。
// DSN 追加 busy_timeout / foreign_keys pragma。
func openSQLite(c ConnReq) (*sql.DB, error) {
	path := c.Database
	if path == "" {
		path = c.Host
	}
	if path == "" {
		return nil, fmt.Errorf("SQLite 需要 database 填文件路径")
	}
	dsn := path
	switch {
	case path == ":memory:":
		// 统一走 file: URI 以便携带 _pragma 参数
		dsn = "file::memory:"
	case strings.HasPrefix(path, "file:"):
		// 调用方自带 URI 参数,不再做存在性检查
	default:
		if _, err := os.Stat(path); err != nil {
			return nil, fmt.Errorf("SQLite 文件不存在: %s", path)
		}
		dsn = "file:" + path
	}
	sep := "?"
	if strings.Contains(dsn, "?") {
		sep = "&"
	}
	dsn += sep + "_pragma=busy_timeout(5000)&_pragma=foreign_keys(1)"
	return sql.Open("sqlite", dsn)
}

func quoteSQLiteIdent(s string) string {
	return `"` + strings.ReplaceAll(s, `"`, `""`) + `"`
}

func listDatabasesSQLite(_ *sql.DB) ([]string, error) {
	return []string{"main"}, nil
}

func listTablesSQLite(ctx context.Context, db *sql.DB, _ string) ([]string, error) {
	rows, err := db.QueryContext(ctx, `SELECT name FROM sqlite_master WHERE type='table' AND name NOT LIKE 'sqlite_%' ORDER BY 1`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	out := []string{}
	for rows.Next() {
		var name string
		if err := rows.Scan(&name); err != nil {
			return nil, err
		}
		out = append(out, name)
	}
	return out, rows.Err()
}

func listColumnsSQLite(ctx context.Context, dbh *sql.DB, _, table string) ([]ColumnInfo, error) {
	rows, err := dbh.QueryContext(ctx, `PRAGMA table_info(`+quoteSQLiteIdent(table)+`)`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()
	var out []ColumnInfo
	for rows.Next() {
		var cid int
		var name, typ string
		var notnull, pk int
		var def sql.NullString
		if err := rows.Scan(&cid, &name, &typ, &notnull, &def, &pk); err != nil {
			return nil, err
		}
		col := ColumnInfo{Name: name, Type: typ, Nullable: notnull == 0}
		if pk > 0 {
			col.Key = "PRI"
		}
		if def.Valid {
			col.Default = def.String
		}
		out = append(out, col)
	}
	if out == nil {
		out = []ColumnInfo{}
	}
	return out, rows.Err()
}