package tokenize

import (
	"testing"
)

func TestFork_CreatesForkOfInputAtSameCursorPosition(t *testing.T) {
	// Create input, accept the first rune.
	i := NewAPI("Testing")
	i.NextRune()
	i.Accept() // T
	AssertEqual(t, "T", i.String(), "accepted rune in input")
	// Fork
	child := i.Fork()
	AssertEqual(t, 1, i.stackFrame.offset, "parent offset")
	AssertEqual(t, 1, i.stackFrame.offset, "child offset")
	// Accept two runes via fork.
	i.NextRune()
	i.Accept() // e
	i.NextRune()
	i.Accept() // s
	AssertEqual(t, "es", i.String(), "result runes in fork")
	AssertEqual(t, 1, i.stackFrames[i.stackLevel-1].offset, "parent offset")
	AssertEqual(t, 3, i.stackFrame.offset, "child offset")
	// Merge fork back into parent
	i.Merge(child)
	i.Dispose(child)
	AssertEqual(t, "Tes", i.String(), "result runes in parent Input after Merge()")
	AssertEqual(t, 3, i.stackFrame.offset, "parent offset")
}

func TestGivenForkedChildWhichAcceptedRune_AfterMerging_RuneEndsUpInParentResult(t *testing.T) {
	i := NewAPI("Testing")
	i.NextRune()
	i.Accept()
	f1 := i.Fork()
	i.NextRune()
	i.Accept()
	f2 := i.Fork()
	i.NextRune()
	i.Accept()
	AssertEqual(t, "s", i.String(), "f2 String()")
	AssertEqual(t, 3, i.stackFrame.offset, "f2.offset A")
	i.Merge(f2)
	i.Dispose(f2)
	AssertEqual(t, "es", i.String(), "f1 String()")
	AssertEqual(t, 3, i.stackFrame.offset, "f1.offset A")
	i.Merge(f1)
	i.Dispose(f1)
	AssertEqual(t, "Tes", i.String(), "top-level API String()")
	AssertEqual(t, 3, i.stackFrame.offset, "f1.offset A")
}

func TestCallingAcceptAfterNextRune_AcceptsRuneAndMovesReadOffsetForward(t *testing.T) {
	i := NewAPI("Testing")
	r, _ := i.NextRune()
	AssertEqual(t, 'T', r, "result from 1st call to NextRune()")
	AssertTrue(t, i.lastRune == 'T', "API.lastRune after NextRune() is not 'T'")
	AssertTrue(t, i.runeRead, "API.runeRead after NextRune() is not true")
	i.Accept()
	AssertTrue(t, i.runeRead == false, "API.runeRead after Accept() is not false")
	AssertEqual(t, 1, i.stackFrame.offset, "API.stackFrame.offset")
	r, _ = i.NextRune()
	AssertEqual(t, 'e', r, "result from 2nd call to NextRune()")
}

func TestFlushInput(t *testing.T) {
	api := NewAPI("cool")

	// Flushing without any read data is okay. FlushInput() will return
	// false in this case, and nothing else happens.
	AssertTrue(t, api.FlushInput() == false, "flush input at start")

	api.NextRune()
	api.Accept()
	api.NextRune()
	api.Accept()

	AssertTrue(t, api.FlushInput() == true, "flush input after reading some data")
	AssertEqual(t, 0, api.stackFrame.offset, "offset after flush input")

	AssertTrue(t, api.FlushInput() == false, "flush input after flush input")

	// Read offset is now zero, but reading should continue after "co".
	api.NextRune()
	api.Accept()
	api.NextRune()
	api.Accept()

	AssertEqual(t, "cool", api.String(), "end result")
}

func TestInputFlusherWrapper(t *testing.T) {
	runeA := A.Rune('a')
	flushB := C.FlushInput(A.Rune('b'))
	api := NewAPI("abaab")
	runeA(api)
	AssertEqual(t, 1, api.stackFrame.offset, "offset after 1 read")
	AssertEqual(t, "a", api.String(), "runes after 1 read")
	flushB(api)
	AssertEqual(t, 0, api.stackFrame.offset, "offset after 2 reads + input flush")
	AssertEqual(t, "ab", api.String(), "runes after 2 reads")
	runeA(api)
	AssertEqual(t, 1, api.stackFrame.offset, "offset after 3 reads")
	AssertEqual(t, "aba", api.String(), "runes after 3 reads")
	runeA(api)
	AssertEqual(t, 2, api.stackFrame.offset, "offset after 4 reads")
	AssertEqual(t, "abaa", api.String(), "runes after 4 reads")
	flushB(api)
	AssertEqual(t, 0, api.stackFrame.offset, "offset after 5 reads + input flush")
	AssertEqual(t, "abaab", api.String(), "runes after 5 reads")
}

func AssertEqual(t *testing.T, expected interface{}, actual interface{}, forWhat string) {
	if expected != actual {
		t.Errorf(
			"Unexpected value for %s:\nexpected: %q\nactual: %q",
			forWhat, expected, actual)
	}
}

func AssertTrue(t *testing.T, b bool, assertion string) {
	if !b {
		t.Errorf("Assertion %s is false", assertion)
	}
}