// Package db provides a lightweight SQLite-backed store for data that
// doesn't fit the plain-file model used by internal/store — currently
// calendar/address-book sharing grants. It's intentionally small: no ORM,
// just database/sql with hand-written queries, so it stays easy to
// extend when user management and the web UI are added later.
package db

import (
	"database/sql"
	"fmt"

	_ "modernc.org/sqlite"
)

// DB wraps a SQLite connection and exposes typed helpers for the
// application's tables.
type DB struct {
	conn *sql.DB
}

// Open opens (creating if necessary) the SQLite database at path and runs
// schema migrations.
func Open(path string) (*DB, error) {
	conn, err := sql.Open("sqlite", path)
	if err != nil {
		return nil, fmt.Errorf("opening database %q: %w", path, err)
	}
	// SQLite only supports one writer at a time; a single connection avoids
	// "database is locked" errors under concurrent access.
	conn.SetMaxOpenConns(1)

	d := &DB{conn: conn}
	if err := d.migrate(); err != nil {
		conn.Close()
		return nil, fmt.Errorf("migrating database: %w", err)
	}
	return d, nil
}

// Close closes the underlying connection.
func (d *DB) Close() error {
	return d.conn.Close()
}

func (d *DB) migrate() error {
	const schema = `
CREATE TABLE IF NOT EXISTS calendar_shares (
	id INTEGER PRIMARY KEY AUTOINCREMENT,
	owner TEXT NOT NULL,
	calendar_name TEXT NOT NULL,
	shared_with TEXT NOT NULL,
	permission TEXT NOT NULL CHECK (permission IN ('read', 'write')),
	created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
	UNIQUE (owner, calendar_name, shared_with)
);

CREATE TABLE IF NOT EXISTS addressbook_shares (
	id INTEGER PRIMARY KEY AUTOINCREMENT,
	owner TEXT NOT NULL,
	addressbook_name TEXT NOT NULL,
	shared_with TEXT NOT NULL,
	permission TEXT NOT NULL CHECK (permission IN ('read', 'write')),
	created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
	UNIQUE (owner, addressbook_name, shared_with)
);
`
	_, err := d.conn.Exec(schema)
	return err
}