// In this example, a parser is created that is able to parse input that looks
// like "Hello, <name>!", and that extracts the name from it.
//
// This implementation uses a state-based Parser for it, and it does not implement
// any custom combinator/parser Matcher functions. Note that things are much easier to
// implement using custom Matchers (see the other HelloWorldUsingMatcher example
// for this). Doing this fully parser-based implementation is mainly for your
// learning pleasure.
//
// One big difference between the Matcher-based example and this one, is that the
// state-based parser reports errors much more fine-grained. This might or might
// not be useful for your specific application.
package parsekit_test

import (
	"fmt"
	"strings"

	"git.makaay.nl/mauricem/go-parsekit"
)

const greeteeItem parsekit.ItemType = 1

func stateStartOfGreeting(p *parsekit.P) {
	c := parsekit.C
	p.Expects("hello")
	if p.On(c.StrNoCase("hello")).Skip() {
		p.RouteTo(stateComma)
	}
}

func stateComma(p *parsekit.P) {
	a := parsekit.A
	p.Expects("comma")
	switch {
	case p.On(a.Whitespace).Skip():
		p.RouteRepeat()
	case p.On(a.Comma).Skip():
		p.RouteTo(stateName)
	}
}

func stateName(p *parsekit.P) {
	a := parsekit.A
	p.Expects("name")
	switch {
	case p.On(a.Excl).Skip():
		p.RouteTo(stateEndOfGreeting)
	case p.On(a.AnyRune).Accept():
		p.RouteRepeat()
	}
}

func stateEndOfGreeting(p *parsekit.P) {
	p.Expects("end of greeting")
	if p.On(a.EndOfFile).Stay() {
		name := strings.TrimSpace(p.BufLiteral())
		if name == "" {
			p.EmitError("The name cannot be empty")
		} else {
			p.Emit(greeteeItem, name)
		}
	}
}

func createHelloParser() *parsekit.Parser {
	return parsekit.NewParser(stateStartOfGreeting)
}

func Example_helloWorldUsingParser() {
	parser := createHelloParser()

	for i, input := range []string{
		"Hello, world!",
		"HELLO ,Johnny!",
		"hello , Bob123!",
		"hello Pizza!",
		"",
		" ",
		"hello",
		"hello,",
		"hello , ",
		"hello , Droopy",
		"hello , Droopy!",
		"hello , \t \t Droopy \t !",
		"Oh no!",
		"hello,!",
	} {
		item, err, ok := parser.Parse(input).Next()
		if !ok {
			fmt.Printf("[%d] Input: %q Error: %s\n", i, input, err)
		} else {
			fmt.Printf("[%d] Input: %q Output: %s\n", i, input, item.Value)
		}
	}
	// Output:
	// [0] Input: "Hello, world!" Output: world
	// [1] Input: "HELLO ,Johnny!" Output: Johnny
	// [2] Input: "hello , Bob123!" Output: Bob123
	// [3] Input: "hello Pizza!" Error: unexpected character 'P' (expected comma)
	// [4] Input: "" Error: unexpected end of file (expected hello)
	// [5] Input: " " Error: unexpected character ' ' (expected hello)
	// [6] Input: "hello" Error: unexpected end of file (expected comma)
	// [7] Input: "hello," Error: unexpected end of file (expected name)
	// [8] Input: "hello , " Error: unexpected end of file (expected name)
	// [9] Input: "hello , Droopy" Error: unexpected end of file (expected name)
	// [10] Input: "hello , Droopy!" Output: Droopy
	// [11] Input: "hello , \t \t Droopy \t !" Output: Droopy
	// [12] Input: "Oh no!" Error: unexpected character 'O' (expected hello)
	// [13] Input: "hello,!" Error: The name cannot be empty
}