/// This package is in charge of connecting to the DB and migrations

package db

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	_ "github.com/mattn/go-sqlite3"
)

var __version = 1

type DbCtx struct {
	db      *sql.DB
	version int
}

func initVersion(tx *sql.Tx) (int, error) {
	var version int
	// Check the version
	if err := tx.QueryRow("PRAGMA user_version").Scan(&version); err != nil {
		tx.Rollback()
		return 0, fmt.Errorf("Could not select user_version. %w", err)
	}

	if version == 0 {
		_, err := tx.Exec(fmt.Sprintf("PRAGMA user_version=%d", __version))
		if err != nil {
			tx.Rollback()
			return 0, fmt.Errorf("Could not update pragma version. %w", err)
		}
		version = __version
	} else if version != __version {
		tx.Rollback()
		return 0, errors.New(fmt.Sprintf("Wrong version. Expected %d got %d", __version, version))
	}
	return version, nil
}

func migration0(tx *sql.Tx) error {
	// Optionally add the version table
	if _, err := tx.Exec(`
		create table if not exists eng_log_version (id integer not null);
	`); err != nil {
		tx.Rollback()
		return fmt.Errorf("Could not create eng_log_version. %w", err)
	}
	// Optionally add the log table
	if _, err := tx.Exec(`
		create table if not exists log (id integer not null primary key, title string)
	`); err != nil {
		tx.Rollback()
		return fmt.Errorf("Could not create log. %w", err)
	}
	return nil
}

func initMigrations(tx *sql.Tx, start_from_versiono int) error {
	var migrations = []func(*sql.Tx) error{migration0}
	for migration_idx, migration := range migrations {
		// Version is 1 indexed, while the migration_idx is 0 indexed
		var migration_num = migration_idx + 1
		if migration_num < start_from_versiono {
			continue
		}
		err := migration(tx)
		if err != nil {
			tx.Rollback()
			return fmt.Errorf("Failed migration %d. %w", migration_num, err)
		}
	}
	return nil
}

func Init(db_location string) (*DbCtx, error) {
	db, err := sql.Open("sqlite3", db_location)
	if err != nil {
		return nil, fmt.Errorf("Could not connect to DB. %w", err)
	}
	if err := db.Ping(); err != nil {
		return nil, fmt.Errorf("Could not ping DB. %w", err)
	}

	ctx := context.Background()
	tx, err := db.BeginTx(ctx, nil)

	if err != nil {
		return nil, err
	}

	version, err := initVersion(tx)
	if err != nil {
		return nil, err
	}

	err = initMigrations(tx, version)
	if err != nil {
		return nil, err
	}

	tx.Commit()

	return &DbCtx{db, version}, nil
}