package parsekit_test

import (
	"fmt"

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

func ExampleTokenAPI_Fork() {
	// This custom TokenHandler checks for a sequence of runes: "abcd"
	// This is done in 4 steps and only after finishing all steps,
	// the TokenHandler will confirm a successful match.
	abcdSequence := func(t *parsekit.TokenAPI) bool {
		child := t.Fork() // fork, so we won't change parent t
		for _, checkRune := range "abcd" {
			readRune, err := child.NextRune()
			if err != nil || readRune != checkRune {
				return false // report mismatch, parent t is left untouched
			}
			child.Accept() // add rune to child output
		}
		child.Merge() // we have a match, add resulting output to parent
		return true   // and report the successful match
	}

	// Note: a custom TokenHandler is normally not what you need.
	// You can make use of the parser/combinator tooling to do things
	// a lot simpler. The handler from above can be replaced with:
	simpler := parsekit.A.Str("abcd")

	result, err := parsekit.NewTokenizer(abcdSequence, "abcd").Execute("abcdefgh")
	fmt.Println(result, err)
	result, err = parsekit.NewTokenizer(simpler, "abcd").Execute("abcdefgh")
	fmt.Println(result, err)
	result, err = parsekit.NewTokenizer(abcdSequence, "abcd").Execute("abcx")
	fmt.Println(result, err)
	result, err = parsekit.NewTokenizer(abcdSequence, "abcd").Execute("xyz")
	fmt.Println(result, err)

	// Output:
	// abcd <nil>
	// abcd <nil>
	// <nil> unexpected character 'a' (expected abcd)
	// <nil> unexpected character 'x' (expected abcd)
}

func ExampleTokenAPI_Merge() {
	tokenHandler := func(t *parsekit.TokenAPI) bool {
		child1 := t.Fork()
		child1.NextRune() // reads 'H'
		child1.Accept()
		child1.NextRune() // reads 'i'
		child1.Accept()

		child2 := child1.Fork()
		child2.NextRune() // reads ' '
		child2.Accept()
		child2.NextRune() // reads 'd'
		child2.Accept()

		child1.Merge() // We merge child1, which has read 'H' and 'i' only.
		return true
	}

	result, _ := parsekit.NewTokenizer(tokenHandler, "a match").Execute("Hi mister X!")
	fmt.Println(result)

	// Output:
	// Hi
}