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// Copyright 2018 Canonical Ltd.
// Licensed under the LGPL, see LICENCE file for details.
package sqlsimplekv
import (
"bytes"
"context"
"database/sql"
"strings"
"text/template"
errgo "gopkg.in/errgo.v1"
)
type tmplID int
const (
_ tmplID = iota - 1
tmplGetKeyValue
tmplGetKeyValueForUpdate
tmplInsertKeyValue
tmplListKeys
numTmpl
)
type queryer interface {
ExecContext(ctx context.Context, query string, args ...interface{}) (sql.Result, error)
QueryContext(ctx context.Context, query string, args ...interface{}) (*sql.Rows, error)
QueryRowContext(ctx context.Context, query string, args ...interface{}) *sql.Row
}
// argBuilder is an interface that can be embedded in template parameters
// to record the arguments needed to be supplied with SQL queries.
type argBuilder interface {
// Arg is a method that is called in templates with the value of
// the next argument to be used in the query. Arg should remmebre
// the value and return a valid placeholder to access that
// argument when executing the query.
Arg(interface{}) string
// args returns the slice of arguments that should be used when
// executing the query.
args() []interface{}
}
type driver struct {
tmpls [numTmpl]*template.Template
argBuilderFunc func() argBuilder
isDuplicate func(error) bool
}
// exec performs the Exec method on the given queryer by processing the
// given template with the given params to determine the query to
// execute.
func (d *driver) exec(ctx context.Context, q queryer, tmplID tmplID, params argBuilder) (sql.Result, error) {
query, err := d.executeTemplate(tmplID, params)
if err != nil {
return nil, errgo.Notef(err, "cannot build query")
}
res, err := q.ExecContext(ctx, query, params.args()...)
return res, errgo.Mask(err, errgo.Any)
}
// query performs the Query method on the given queryer by processing the
// given template with the given params to determine the query to
// execute.
func (d *driver) query(ctx context.Context, q queryer, tmplID tmplID, params argBuilder) (*sql.Rows, error) {
query, err := d.executeTemplate(tmplID, params)
if err != nil {
return nil, errgo.Notef(err, "cannot build query")
}
rows, err := q.QueryContext(ctx, query, params.args()...)
return rows, errgo.Mask(err, errgo.Any)
}
// queryRow performs the QueryRow method on the given queryer by
// processing the given template with the given params to determine the
// query to execute.
func (d *driver) queryRow(ctx context.Context, q queryer, tmplID tmplID, params argBuilder) (*sql.Row, error) {
query, err := d.executeTemplate(tmplID, params)
if err != nil {
return nil, errgo.Notef(err, "cannot build query")
}
return q.QueryRowContext(ctx, query, params.args()...), nil
}
func (d *driver) parseTemplate(tmplID tmplID, tmpl string) error {
var err error
d.tmpls[tmplID], err = template.New("").Funcs(template.FuncMap{
"join": strings.Join,
}).Parse(tmpl)
return errgo.Mask(err)
}
func (d *driver) executeTemplate(tmplID tmplID, params argBuilder) (string, error) {
var buf bytes.Buffer
if err := d.tmpls[tmplID].Execute(&buf, params); err != nil {
return "", errgo.Mask(err)
}
return buf.String(), nil
}
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