// Package store is geniusrun's SQLite persistence layer: activities, laps,
// per-second samples, workout kind rule config, and classification history.
package store

import (
	"database/sql"
	_ "embed"
	"fmt"

	_ "modernc.org/sqlite"
)

//go:embed schema.sql
var schemaSQL string

// DB wraps a *sql.DB opened against a geniusrun SQLite database file, with
// the schema already applied.
type DB struct {
	*sql.DB
}

// Open opens (creating if needed) the SQLite database at path and applies
// schema.sql if it hasn't been applied yet. There is no migration history --
// this is a pre-production app with no compatibility obligation to older
// database files. Edit schema.sql directly to change the schema.
func Open(path string) (*DB, error) {
	sqlDB, err := sql.Open("sqlite", path+"?_pragma=foreign_keys(1)")
	if err != nil {
		return nil, fmt.Errorf("open sqlite database: %w", err)
	}
	// SQLite only supports one writer at a time; a single connection avoids
	// "database is locked" errors under any concurrent access from the app.
	sqlDB.SetMaxOpenConns(1)

	db := &DB{DB: sqlDB}
	if err := db.applySchema(); err != nil {
		sqlDB.Close()
		return nil, err
	}
	return db, nil
}

// applySchema runs schema.sql once, the first time this database file is
// opened -- detected by checking whether the users table already exists.
func (db *DB) applySchema() error {
	var alreadyApplied int
	if err := db.QueryRow(`SELECT COUNT(*) FROM sqlite_master WHERE type='table' AND name='users'`).Scan(&alreadyApplied); err != nil {
		return fmt.Errorf("check existing schema: %w", err)
	}
	if alreadyApplied > 0 {
		return nil
	}

	tx, err := db.Begin()
	if err != nil {
		return fmt.Errorf("begin schema tx: %w", err)
	}
	defer tx.Rollback()

	if _, err := tx.Exec(schemaSQL); err != nil {
		return fmt.Errorf("apply schema: %w", err)
	}
	return tx.Commit()
}