adapter.go

/*
    This package is responsible for converting ? placeholders into
    $i placeholders, like MySQL to PostgesQL.
*/

package modeldb

import (
    . "github.com/jaekwon/pego"
    "fmt"
    "strings"
)

var phConversions = map[string]string{}

var phGrammar = Grm("S", map[string]*Pattern{
    "S": Seq(
        Ref("OTHER"),
        Seq(
            Ref("PH").Or(Ref("STR")),
            Ref("OTHER"),
        ).Rep(0, -1),
    ).Clist(),
    "OTHER": NegSet("'?").Rep(0, -1).Csimple(),
    "PH": Char('?').Csimple(),
    "STR": Seq(
        Char('\''),
        Seq(
            Seq(Char('\\'), Any(1)).Or(
                NegSet("'")),
        ).Rep(0, -1),
        Char('\''),
    ).Csimple(),
})

func ReplacePH(items []interface{}) string {
    index := 1
    parts := []string{}
    for _, item := range items {
        if item == "?" {
            parts = append(parts, fmt.Sprintf("$%v", index))
            index++
        } else {
            parts = append(parts, item.(string))
        }
    }
    //fmt.Println(">> %v", strings.Join(parts, ""))
    return strings.Join(parts, "")
}

func ConvertPH(q string) string {
    if phConversions[q] != "" {
        return phConversions[q]
    }
    r, err, _ := Match(phGrammar, q)
    if err != nil { panic(err) }
    return ReplacePH(r.([]interface{}))
}