has.go

package bob

import (
	"errors"
	"strings"

	"github.com/lann/builder"
)

type HasBuilder builder.Builder

type hasData struct {
	Name        string
	Column      string
	Schema      string
	Placeholder string
}

func init() {
	builder.Register(HasBuilder{}, hasData{})
}

// HasTable checks for a table's existence by tableName,
// resolving with a boolean to signal if the table exists.
func (h HasBuilder) HasTable(table string) HasBuilder {
	return builder.Set(h, "Name", table).(HasBuilder)
}

// HasColumn checks if a column exists in the current table,
// resolves the promise with a boolean, true if the column exists, false otherwise.
func (h HasBuilder) HasColumn(column string) HasBuilder {
	return builder.Set(h, "Column", column).(HasBuilder)
}

// WithSchema specifies the schema to be used when using the schema-building commands.
func (h HasBuilder) WithSchema(schema string) HasBuilder {
	return builder.Set(h, "Schema", schema).(HasBuilder)
}

// PlaceholderFormat changes the default placeholder (?) to desired placeholder.
func (h HasBuilder) PlaceholderFormat(f string) HasBuilder {
	return builder.Set(h, "Placeholder", f).(HasBuilder)
}

// ToSql returns 3 variables filled out with the correct values based on bindings, etc.
func (h HasBuilder) ToSql() (string, []interface{}, error) {
	data := builder.GetStruct(h).(hasData)
	return data.ToSql()
}

// ToSql returns 3 variables filled out with the correct values based on bindings, etc.
func (d *hasData) ToSql() (sqlStr string, args []interface{}, err error) {
	var sql strings.Builder
	if d.Name == "" {
		err = errors.New("has statement should have a table name")
		return
	}

	if d.Column != "" && d.Name != "" {
		// search for column
		sql.WriteString("SELECT * FROM information_schema.columns WHERE table_name = ? AND column_name = ?")
	} else if d.Name != "" && d.Column == "" {
		sql.WriteString("SELECT * FROM information_schema.tables WHERE table_name = ?")
	}

	if d.Schema != "" {
		sql.WriteString(" AND table_schema = ?;")
	} else {
		sql.WriteString(" AND table_schema = current_schema();")
	}

	sqlStr = ReplacePlaceholder(sql.String(), d.Placeholder)
	args = createArgs(d.Name, d.Column, d.Schema)
	return
}