// This is the same as the other hello examples, except that in this
// implementation the state machine is implemented using a combination of some
// Handlers and only a single state, in which multiple API.On() calls
// are combined to do all the work in one go.
//
// Note that things are much easier to implement using custom Handlers (see
// the other helloParserCombinator example for this). Doing this implementation
// is mainly for your learning pleasure.
//
// One big difference between the parser/combinator-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.

package examples

import (
	"fmt"

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

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 at line 1, column 6
	// [4] Input: "" Error: the greeting is not being friendly at start of file
	// [5] Input: " " Error: the greeting is not being friendly at start of file
	// [6] Input: "hello" Error: the greeting is not properly separated at line 1, column 6
	// [7] Input: "hello," Error: the greeting is targeted at thin air at line 1, column 7
	// [8] Input: "hello , " Error: the greeting is targeted at thin air at line 1, column 9
	// [9] Input: "hello , Droopy" Error: the greeting is not loud enough at line 1, column 15
	// [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 at start of file
	// [13] Input: "hello,!" Error: the greeting is targeted at thin air at line 1, column 7
	// [14] Input: "HELLO, Buster! Eat this!" Error: too much stuff going on after the closing '!' at line 1, column 15
}

// ―――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――
// Implementation of the parser
// ―――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――――

type helloparser2 struct {
	greetee string
}

func (h *helloparser2) Parse(input string) (string, error) {
	parseHello := parse.New(h.start)
	err := parseHello(input)
	return h.greetee, err
}

func (h *helloparser2) start(p *parse.API) {
	c, a, m := tokenize.C, tokenize.A, tokenize.M
	if !p.Accept(a.StrNoCase("hello")) {
		p.Error("the greeting is not being friendly")
		return
	}
	if !p.Accept(c.Seq(c.Opt(a.Blank), a.Comma, c.Opt(a.Blank))) {
		p.Error("the greeting is not properly separated")
		return
	}
	if p.Accept(m.TrimSpace(c.OneOrMore(c.Except(a.Excl, a.AnyRune)))) {
		h.greetee = p.Result().String()
		if h.greetee == "" {
			p.Error("the name cannot be empty")
			return
		}
	} else {
		p.Error("the greeting is targeted at thin air")
		return
	}
	if !p.Accept(a.Excl) {
		p.Error("the greeting is not loud enough")
	} else if !p.Accept(a.EndOfFile) {
		p.Error("too much stuff going on after the closing '!'")
	} else {
		p.Stop()
	}
}