blob: 930c140418bddb5e9d07a5cb7708508a38043964 [file] [log] [blame]
// Copyright 2015 The Vanadium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Package reader provides an object that reads queries from various input
// sources (e.g. stdin, pipe).
package reader
import (
"bufio"
"os"
"strings"
"text/scanner"
"github.com/peterh/liner"
)
type T struct {
s scanner.Scanner
prompt prompter
}
func newT(prompt prompter) *T {
t := &T{prompt: prompt}
t.initScanner("")
return t
}
// Close frees any resources acquired by this reader.
func (t *T) Close() {
t.prompt.Close()
}
func (t *T) initScanner(input string) {
t.s.Init(strings.NewReader(input))
// Keep all whitespace.
t.s.Whitespace = 0
}
// GetQuery returns an entire query where queries are delimited by semicolons.
// GetQuery returns the error io.EOF when there is no more input.
func (t *T) GetQuery() (string, error) {
if t.s.Peek() == scanner.EOF {
input, err := t.prompt.InitialPrompt()
if err != nil {
return "", err
}
t.initScanner(input)
}
var query string
WholeQuery:
for true {
for tok := t.s.Scan(); tok != scanner.EOF; tok = t.s.Scan() {
if tok == ';' {
break WholeQuery
}
query += t.s.TokenText()
}
input, err := t.prompt.ContinuePrompt()
if err != nil {
return "", err
}
t.initScanner(input)
query += "\n" // User started a new line.
}
t.prompt.AppendHistory(query + ";")
return query, nil
}
type prompter interface {
Close()
InitialPrompt() (string, error)
ContinuePrompt() (string, error)
AppendHistory(query string)
}
// noninteractive prompter just blindly reads from stdin.
type noninteractive struct {
input *bufio.Reader
}
// NewNonInteractive returns a T that simply reads input from stdin. Useful
// for when the user is piping input from a file or another program.
func NewNonInteractive() *T {
return newT(&noninteractive{bufio.NewReader(os.Stdin)})
}
func (i *noninteractive) Close() {
}
func (i *noninteractive) InitialPrompt() (string, error) {
return i.input.ReadString('\n')
}
func (i *noninteractive) ContinuePrompt() (string, error) {
return i.input.ReadString('\n')
}
func (i *noninteractive) AppendHistory(query string) {
}
// interactive prompter provides a nice prompt for a user to input queries.
type interactive struct {
line *liner.State
}
// NewInteractive returns a T that prompts the user for input.
func NewInteractive() *T {
i := &interactive{
line: liner.NewLiner(),
}
i.line.SetCtrlCAborts(true)
return newT(i)
}
func (i *interactive) Close() {
i.line.Close()
}
func (i *interactive) InitialPrompt() (string, error) {
return i.line.Prompt("? ")
}
func (i *interactive) ContinuePrompt() (string, error) {
return i.line.Prompt(" > ")
}
func (i *interactive) AppendHistory(query string) {
i.line.AppendHistory(query)
}