package store

import (
	"database/sql"
	"fmt"
	"time"
)

// Option configures Open.
type Option func(*options)

type options struct {
	autoMigrate          bool
	changeBatchRetention time.Duration
}

// OpenDB opens the SQLite database at path with the store's connection
// settings (foreign keys, WAL, busy timeout, immediate transactions). The
// file is created on first use. Use it for anything that works on the store's
// database directly, such as running migrations.
func OpenDB(path string) (*sql.DB, error) {
	return sql.Open("sqlite3", dsn(path))
}

// WithAutoMigrate makes Open apply pending migrations instead of returning
// ErrNeedsMigration. Intended for tests and throwaway databases; applications
// should migrate explicitly with the migrate command.
func WithAutoMigrate() Option {
	return func(opts *options) {
		opts.autoMigrate = true
	}
}

// WithChangeBatchRetention makes the store delete change batches older than
// retention whenever it records a new one, so a client can catch up from a
// batch for that long (see ListChangedOpportunities). Without it, or with 0
// or less, batches are kept for ever.
func WithChangeBatchRetention(retention time.Duration) Option {
	return func(opts *options) {
		opts.changeBatchRetention = retention
	}
}

// dsn builds the mattn/go-sqlite3 connection string.
//
//   - _foreign_keys: SQLite ignores REFERENCES clauses unless this is on.
//   - _journal_mode=WAL: readers don't block the writer or each other.
//   - _busy_timeout: wait for a lock rather than failing immediately.
//   - _txlock=immediate: transactions take the write lock at BEGIN, so a
//     read-then-write transaction (as in SaveOpportunity) can't fail with
//     SQLITE_BUSY halfway through.
func dsn(path string) string {
	return fmt.Sprintf(
		"file:%s?_foreign_keys=on&_journal_mode=WAL&_busy_timeout=5000&_txlock=immediate",
		path,
	)
}