package sessionimport

import (
	"crypto/sha1"
	"database/sql"
	"fmt"

	"github.com/gotd/td/session"
	_ "modernc.org/sqlite"
)

// ConvertPyrogramSession reads a Pyrogram/Telethon SQLite session file and
// builds a gotd/td session.Data representing the same authorization.
//
// Pyrogram schema (single row in `sessions` table):
//
//	CREATE TABLE sessions (
//	  dc_id     INTEGER PRIMARY KEY,
//	  api_id    INTEGER,
//	  test_mode INTEGER,
//	  auth_key  BLOB,         -- 256 bytes
//	  date      INTEGER NOT NULL,
//	  user_id   INTEGER,
//	  is_bot    INTEGER);
func ConvertPyrogramSession(sqlitePath string) (*session.Data, error) {
	// Open READ-ONLY + IMMUTABLE. Pyrogram .session files may be in-use by a
	// running Pyrogram client; a write-capable handle could corrupt them via
	// journal rollback on crash.
	dsn := fmt.Sprintf("file:%s?mode=ro&immutable=1", sqlitePath)
	db, err := sql.Open("sqlite", dsn)
	if err != nil {
		return nil, fmt.Errorf("open pyrogram sqlite: %w", err)
	}
	defer db.Close()

	var dcID int
	var authKey []byte
	err = db.QueryRow(`SELECT dc_id, auth_key FROM sessions LIMIT 1`).Scan(&dcID, &authKey)
	if err != nil {
		return nil, fmt.Errorf("read pyrogram sessions row: %w", err)
	}
	if len(authKey) != 256 {
		return nil, fmt.Errorf("invalid auth_key length: %d (want 256)", len(authKey))
	}

	addr, err := TGDCAddr(dcID)
	if err != nil {
		return nil, err
	}

	// auth_key_id = SHA-1(auth_key)[12:20] — lower 64 bits of the SHA-1 digest.
	sum := sha1.Sum(authKey)
	keyID := make([]byte, 8)
	copy(keyID, sum[12:20])

	return &session.Data{
		DC:        dcID,
		Addr:      addr,
		AuthKey:   authKey,
		AuthKeyID: keyID,
	}, nil
}