package parsekit

import (
	"io"
	"strings"
	"testing"
	"unicode/utf8"
)

func TestCallingNextRune_ReturnsNextRune(t *testing.T) {
	r, _ := mkInput().NextRune()
	AssertEqual(t, 'T', r, "first rune")
}

func TestInputCanAcceptRunesFromReader(t *testing.T) {
	i := mkInput()
	i.NextRune()
	i.Accept()
	i.NextRune()
	i.Accept()
	i.NextRune()
	i.Accept()
	AssertEqual(t, "Tes", i.Result().String(), "i.Result().String()")
}

func TestCallingNextRuneTwice_Panics(t *testing.T) {
	AssertPanic(t, PanicT{
		Function: func() {
			i := mkInput()
			i.NextRune()
			i.NextRune()
		},
		Regexp: true,
		Expect: `parsekit\.TokenAPI\.NextRune\(\): NextRune\(\) called at ` +
			`/.*/tokenizer_test\.go:\d+ without a prior call to Accept\(\)`,
	})
}

func TestCallingAcceptWithoutCallingNextRune_Panics(t *testing.T) {
	AssertPanic(t, PanicT{
		Function: mkInput().Accept,
		Regexp:   true,
		Expect: `parsekit\.TokenAPI\.Accept\(\): Accept\(\) called ` +
			`at /.*/assertions_test\.go:\d+ without first calling NextRune()`,
	})
}

func TestCallingMergeOnNonForkedChild_Panics(t *testing.T) {
	AssertPanic(t, PanicT{
		Function: func() {
			i := mkInput()
			i.Merge()
		},
		Regexp: true,
		Expect: `parsekit\.TokenAPI\.Merge\(\): Merge\(\) called at ` +
			`/.*/tokenizer_test\.go:\d+ on a non-forked TokenAPI`})
}

func TestCallingNextRuneOnForkedParent_DetachesForkedChild(t *testing.T) {
	AssertPanic(t, PanicT{
		Function: func() {
			i := mkInput()
			f := i.Fork()
			i.NextRune()
			f.Merge()
		},
		Regexp: true,
		Expect: `parsekit\.TokenAPI\.Merge\(\): Merge\(\) called at ` +
			`/.*/tokenizer_test\.go:\d+ on a non-forked TokenAPI`})
}

func TestCallingForkOnForkedParent_DetachesForkedChild(t *testing.T) {
	AssertPanic(t, PanicT{
		Function: func() {
			i := mkInput()
			f := i.Fork()
			i.Fork()
			f.Merge()
		},
		Regexp: true,
		Expect: `parsekit\.TokenAPI\.Merge\(\): Merge\(\) called at ` +
			`/.*/tokenizer_test\.go:\d+ on a non-forked TokenAPI`})
}

func TestGivenMultipleLevelsOfForks_WhenReturningToRootInput_ForksAreDetached(t *testing.T) {
	i := mkInput()
	f1 := i.Fork()
	f2 := f1.Fork()
	f3 := f2.Fork()
	f4 := f1.Fork() // secret subtest: this Fork() detaches both forks f2 and f3
	f5 := f4.Fork()
	AssertEqual(t, true, i.parent == nil, "i.parent == nil")
	AssertEqual(t, true, i.child == f1, "i.child == f1")
	AssertEqual(t, true, f1.parent == i, "f1.parent == i")
	AssertEqual(t, true, f1.child == f4, "f1.child == f4")
	AssertEqual(t, true, f2.child == nil, "f2.child == nil")
	AssertEqual(t, true, f2.parent == nil, "f2.parent == nil")
	AssertEqual(t, true, f3.child == nil, "f3.child == nil")
	AssertEqual(t, true, f3.parent == nil, "f3.parent == nil")
	AssertEqual(t, true, f4.parent == f1, "f4.parent == f1")
	AssertEqual(t, true, f4.child == f5, "f4.child == f5")
	AssertEqual(t, true, f5.parent == f4, "f5.parent == f4")
	AssertEqual(t, true, f5.child == nil, "f5.child == nil")

	i.NextRune()

	AssertEqual(t, true, i.parent == nil, "i.parent == nil")
	AssertEqual(t, true, i.child == nil, "i.child == nil")
	AssertEqual(t, true, f1.parent == nil, "f1.parent == nil")
	AssertEqual(t, true, f1.child == nil, "f1.child == nil")
	AssertEqual(t, true, f2.child == nil, "f2.child == nil")
	AssertEqual(t, true, f2.parent == nil, "f2.parent == nil")
	AssertEqual(t, true, f3.child == nil, "f3.child == nil")
	AssertEqual(t, true, f3.parent == nil, "f3.parent == nil")
	AssertEqual(t, true, f4.parent == nil, "f4.parent == nil")
	AssertEqual(t, true, f4.child == nil, "f4.child == nil")
	AssertEqual(t, true, f5.parent == nil, "f5.parent == nil")
	AssertEqual(t, true, f5.child == nil, "f5.child == nil")
}

func TestForkingInput_ClearsLastRune(t *testing.T) {
	AssertPanic(t, PanicT{
		Function: func() {
			i := mkInput()
			i.NextRune()
			i.Fork()
			i.Accept()
		},
		Regexp: true,
		Expect: `parsekit\.TokenAPI\.Accept\(\): Accept\(\) called ` +
			`at /hom.*/tokenizer_test\.go:\d+ without first calling NextRune\(\)`,
	})
}

func TestCallingAcceptAfterNextRune_AcceptsRuneAndMovesReadOffsetForward(t *testing.T) {
	i := mkInput()
	r, _ := i.NextRune()
	AssertEqual(t, 'T', r, "result from 1st call to NextRune()")
	AssertTrue(t, i.result.lastRune != nil, "Input.lastRune after NextRune() is not nil")
	i.Accept()
	AssertTrue(t, i.result.lastRune == nil, "Input.lastRune after Accept() is nil")
	AssertEqual(t, 1, i.offset, "Input.offset")
	AssertEqual(t, 'T', i.reader.buffer[0], "Input.buffer[0]")
	r, _ = i.NextRune()
	AssertEqual(t, 'e', r, "result from 2nd call to NextRune()")
}

func TestCallingMultipleAccepts_FillsInputWithData(t *testing.T) {
	i := mkInput()
	for j := 0; j < 7; j++ {
		i.NextRune()
		i.Accept()
	}
	AssertEqual(t, "Testing", string(i.reader.buffer), "reader input buffer")
	AssertEqual(t, "Testing", i.Result().String(), "i.Result().String()")
}

func TestAccept_UpdatesCursor(t *testing.T) {
	i := NewTokenAPI(strings.NewReader("input\r\nwith\r\nnewlines"))
	AssertEqual(t, "start of file", i.cursor.String(), "cursor 1")
	for j := 0; j < 6; j++ { // read "input\r", cursor end up at "\n"
		i.NextRune()
		i.Accept()
	}
	AssertEqual(t, "line 1, column 7", i.cursor.String(), "cursor 2")
	i.NextRune() // read "\n", cursor ends up at start of new line
	i.Accept()
	AssertEqual(t, "line 2, column 1", i.cursor.String(), "cursor 3")
	for j := 0; j < 10; j++ { // read "with\r\nnewl", cursor end up at "i"
		i.NextRune()
		i.Accept()
	}
	AssertEqual(t, "line 3, column 5", i.cursor.String(), "cursor 4")
	AssertEqual(t, *i.cursor, i.Cursor(), "i.Cursor()")
}

func TestFork_CreatesForkOfInputAtSameCursorPosition(t *testing.T) {
	// Create input, accept the first rune.
	i := mkInput()
	i.NextRune()
	i.Accept() // T
	AssertEqual(t, "T", i.Result().String(), "accepted rune in input")
	// Fork
	f := i.Fork()
	AssertEqual(t, f, i.child, "Input.child (must be f)")
	AssertEqual(t, i, f.parent, "Input.parent (must be i)")
	AssertEqual(t, 1, i.cursor.Byte, "i.child.cursor.Byte")
	AssertEqual(t, 1, i.child.cursor.Byte, "i.child.cursor.Byte")
	// Accept two runes via fork.
	f.NextRune()
	f.Accept() // e
	f.NextRune()
	f.Accept() // s
	AssertEqual(t, "es", f.Result().String(), "result runes in fork")
	AssertEqual(t, 1, i.cursor.Byte, "i.child.cursor.Byte")
	AssertEqual(t, 3, i.child.cursor.Byte, "i.child.cursor.Byte")
	// Merge fork back into parent
	f.Merge()
	AssertEqual(t, "Tes", i.Result().String(), "result runes in parent Input after Merge()")
	AssertEqual(t, 3, i.cursor.Byte, "i.child.cursor.Byte")
}

func TestGivenForkedChildWhichAcceptedRune_AfterMerging_RuneEndsUpInParentResult(t *testing.T) {
	i := mkInput()
	i.NextRune()
	i.Accept()
	f1 := i.Fork()
	f1.NextRune()
	f1.Accept()
	f2 := f1.Fork()
	f2.NextRune()
	f2.Accept()
	AssertEqual(t, "T", i.Result().String(), "i.Result().String()")
	AssertEqual(t, 1, i.offset, "i.offset")
	AssertEqual(t, "e", f1.Result().String(), "f1.Result().String()")
	AssertEqual(t, 2, f1.offset, "f1.offset")
	AssertEqual(t, "s", f2.Result().String(), "f2.Result().String()")
	AssertEqual(t, 3, f2.offset, "f2.offset")
	f2.Merge()
	AssertEqual(t, "T", i.Result().String(), "i.Result().String()")
	AssertEqual(t, 1, i.offset, "i.offset")
	AssertEqual(t, "es", f1.Result().String(), "f1.Result().String()")
	AssertEqual(t, 3, f1.offset, "f1.offset")
	AssertEqual(t, "", f2.Result().String(), "f2.Result().String()")
	AssertEqual(t, 3, f2.offset, "f2.offset")
	f1.Merge()
	AssertEqual(t, "Tes", i.Result().String(), "i.Result().String()")
	AssertEqual(t, 3, i.offset, "i.offset")
	AssertEqual(t, "", f1.Result().String(), "f1.Result().String()")
	AssertEqual(t, 3, f1.offset, "f1.offset")
	AssertEqual(t, "", f2.Result().String(), "f2.Result().String()")
	AssertEqual(t, 3, f2.offset, "f2.offset")
}

func TestWhenCallingNextruneAtEndOfFile_EOFIsReturned(t *testing.T) {
	i := NewTokenAPI(strings.NewReader("X"))
	i.NextRune()
	i.Accept()
	r, err := i.NextRune()
	AssertEqual(t, true, r == utf8.RuneError, "returned rune from NextRune()")
	AssertEqual(t, true, err == io.EOF, "returned error from NextRune()")
}
func TestAfterReadingruneAtEndOfFile_EarlierRunesCanStillBeAccessed(t *testing.T) {
	i := NewTokenAPI(strings.NewReader("X"))
	f := i.Fork()
	f.NextRune()
	f.Accept()
	r, err := f.NextRune()
	AssertEqual(t, true, r == utf8.RuneError, "returned rune from 2nd NextRune()")
	r, err = i.NextRune()
	AssertEqual(t, 'X', r, "returned rune from 2nd NextRune()")
	AssertEqual(t, true, err == nil, "returned error from 2nd NextRune()")
}

func mkInput() *TokenAPI {
	return NewTokenAPI(strings.NewReader("Testing"))
}