// This is the same as the example HelloWorldUsingParser1, except that in this
// implementation the state machine is implemented using a combination of some
// TokenHandlers and only a single state, in which multiple ParseAPI.On() calls
// are combined to do all the work in one go.
//
// Note that things are much easier to implement using custom TokenHandlers (see
// the other HelloWorldUsingMatcher example for this). Doing this implementation
// is mainly for your learning pleasure.
//
// One big difference between the Matcher-based example and this one, is that
// this parser reports errors much more fine-grained. This might or might not be
// useful for your specific use case.:0

package parsekit_test

import (
	"fmt"

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

func Example_helloWorldUsingParser2() {
	parser := &helloparser2{}

	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,!",
		"HELLO, Buster! Eat this!",
	} {
		name, err := parser.Parse(input)
		if err != nil {
			fmt.Printf("[%d] Input: %q Error: %s\n", i, input, err)
		} else {
			fmt.Printf("[%d] Input: %q Output: %s\n", i, input, name)
		}
	}
	// Output:
	// [0] Input: "Hello, world!" Output: world
	// [1] Input: "HELLO ,Johnny!" Output: Johnny
	// [2] Input: "hello , Bob123!" Output: Bob123
	// [3] Input: "hello Pizza!" Error: the greeting is not properly separated
	// [4] Input: "" Error: the greeting is not being friendly
	// [5] Input: " " Error: the greeting is not being friendly
	// [6] Input: "hello" Error: the greeting is not properly separated
	// [7] Input: "hello," Error: the greeting is targeted at thin air
	// [8] Input: "hello , " Error: the greeting is targeted at thin air
	// [9] Input: "hello , Droopy" Error: the greeting is not loud enough
	// [10] Input: "hello , Droopy!" Output: Droopy
	// [11] Input: "hello , \t \t Droopy \t !" Output: Droopy
	// [12] Input: "Oh no!" Error: the greeting is not being friendly
	// [13] Input: "hello,!" Error: the greeting is targeted at thin air
	// [14] Input: "HELLO, Buster! Eat this!" Error: too much stuff going on after the closing '!'
}

// ---------------------------------------------------------------------------
// Implementation of the parser
// ---------------------------------------------------------------------------

type helloparser2 struct {
	greetee string
}

func (h *helloparser2) Parse(input string) (string, *parsekit.Error) {
	parser := parsekit.NewParser(h.start)
	err := parser.Execute(input)
	return h.greetee, err
}

// Note:
// For efficiency, we could have either:
//
// 1) added a return after every call to p.EmitError()
// 2) done an 'else if' for every 'if' after the first
//
// For code readability, I omitted these however. The ParseAPI knows it
// should ignore any upcoming call after an error has been set, so after
// an error the p.On() calls will be invoked, however they will always
// return false.
func (h *helloparser2) start(p *parsekit.ParseAPI) {
	c, a, m := parsekit.C, parsekit.A, parsekit.M
	if !p.On(c.StrNoCase("hello")).Skip() {
		p.EmitError("the greeting is not being friendly")
	} else if !p.On(c.Seq(c.Opt(a.Whitespace), a.Comma, c.Opt(a.Whitespace))).Skip() {
		p.EmitError("the greeting is not properly separated")
	} else if !p.On(m.TrimSpace(c.OneOrMore(c.Except(a.Excl, a.AnyRune)))).Accept() {
		p.EmitError("the greeting is targeted at thin air")
	} else if !p.On(a.Excl).Skip() {
		p.EmitError("the greeting is not loud enough")
	} else if !p.On(a.EndOfFile).Stay() {
		p.EmitError("too much stuff going on after the closing '!'")
	} else {
		h.greetee = p.BufLiteral()
		if h.greetee == "" {
			p.EmitError("the name cannot be empty")
		}
		p.Stop()
	}
}