Fs02/rel

// Package mysql wraps mysql driver as an adapter for REL.
//
// Usage:
//    // open mysql connection.
//    adapter, err := mysql.Open("root@(127.0.0.1:3306)/rel_test?charset=utf8&parseTime=True&loc=Local")
//    if err != nil {
//        panic(err)
//    }
//    defer adapter.Close()
//
//    // initialize REL's repo.
//    repo := rel.New(adapter)
package mysql

import (
    db "database/sql"
    "strings"

    "github.com/Fs02/rel"
    "github.com/Fs02/rel/adapter/sql"
)

// Adapter definition for mysql database.
type Adapter struct {
    *sql.Adapter
}

var (
    _ rel.Adapter = (*Adapter)(nil)

    // Config for mysql adapter.
    Config = sql.Config{
        DropIndexOnTable: true,
        Placeholder:      "?",
        EscapeChar:       "`",
        IncrementFunc:    incrementFunc,
        ErrorFunc:        errorFunc,
        MapColumnFunc:    sql.MapColumn,
    }
)

// New mysql adapter using existing connection.
func New(database *db.DB) *Adapter {
    return &Adapter{
        Adapter: &sql.Adapter{
            Config: Config,
            DB:     database,
        },
    }
}

// Open mysql connection using dsn.
func Open(dsn string) (*Adapter, error) {
    // force clientFoundRows=true
    // this allows not found record check when updating a record.
    if strings.ContainsRune(dsn, '?') {
        dsn += "&clientFoundRows=true"
    } else {
        dsn += "?clientFoundRows=true"
    }

    var database, err = db.Open("mysql", dsn)
    return New(database), err
}

func incrementFunc(adapter sql.Adapter) int {
    var variable string
    var increment int
    var err error
    if adapter.Tx != nil {
        err = adapter.Tx.QueryRow("SHOW VARIABLES LIKE 'auto_increment_increment';").Scan(&variable, &increment)
    } else {
        err = adapter.DB.QueryRow("SHOW VARIABLES LIKE 'auto_increment_increment';").Scan(&variable, &increment)
    }

    check(err)

    return increment
}

func errorFunc(err error) error {
    if err == nil {
        return nil
    }

    var (
        msg          = err.Error()
        errCodeSep   = ':'
        errCodeIndex = strings.IndexRune(msg, errCodeSep)
    )

    if errCodeIndex < 0 {
        errCodeIndex = 0
    }

    switch msg[:errCodeIndex] {
    case "Error 1062":
        return rel.ConstraintError{
            Key:  sql.ExtractString(msg, "key '", "'"),
            Type: rel.UniqueConstraint,
            Err:  err,
        }
    case "Error 1452":
        return rel.ConstraintError{
            Key:  sql.ExtractString(msg, "CONSTRAINT `", "`"),
            Type: rel.ForeignKeyConstraint,
            Err:  err,
        }
    default:
        return err
    }
}

func check(err error) {
    if err != nil {
        panic(err)
    }
}