// Copyright (C) 2022-2023  Luke Shumaker <lukeshu@lukeshu.com>
//
// SPDX-License-Identifier: GPL-2.0-or-later

package lowmemjson

import (
	"fmt"
	"io"
	"strings"
	"testing"

	"github.com/stretchr/testify/assert"

	"git.lukeshu.com/go/lowmemjson/internal/jsonparse"
)

type ReadRuneTypeResult struct {
	r rune
	s int
	t jsonparse.RuneType
	e error
}

const (
	unreadRune      = -1
	pushReadBarrier = -2
	popReadBarrier  = -3
	reset           = -4
)

func (r ReadRuneTypeResult) String() string {
	switch r.s {
	case unreadRune:
		return fmt.Sprintf("{%q, unreadRune, %#v, %v}", r.r, r.t, r.e)
	case pushReadBarrier:
		return fmt.Sprintf("{%q, pushReadBarrier, %#v, %v}", r.r, r.t, r.e)
	case popReadBarrier:
		return fmt.Sprintf("{%q, popReadBarrier, %#v, %v}", r.r, r.t, r.e)
	case reset:
		return fmt.Sprintf("{%q, reset, %#v, %v}", r.r, r.t, r.e)
	default:
		return fmt.Sprintf("{%q, %d, %#v, %v}", r.r, r.s, r.t, r.e)
	}
}

type runeTypeScannerTestcase struct {
	Input        string
	ExpRemainder string
	Exp          []ReadRuneTypeResult
}

func TestRuneTypeScanner(t *testing.T) {
	t.Parallel()
	testcases := map[string]runeTypeScannerTestcase{
		"basic": {`{"foo": 12.0}`, ``, []ReadRuneTypeResult{
			{'{', 1, jsonparse.RuneTypeObjectBeg, nil},
			{'"', 1, jsonparse.RuneTypeStringBeg, nil},
			{'f', 1, jsonparse.RuneTypeStringChar, nil},
			{'o', 1, jsonparse.RuneTypeStringChar, nil},
			{'o', 1, jsonparse.RuneTypeStringChar, nil},
			{'"', 1, jsonparse.RuneTypeStringEnd, nil},
			{':', 1, jsonparse.RuneTypeObjectColon, nil},
			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{'2', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{'.', 1, jsonparse.RuneTypeNumberFracDot, nil},
			{'0', 1, jsonparse.RuneTypeNumberFracDig, nil},
			{'}', 1, jsonparse.RuneTypeObjectEnd, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
		}},
		"unread": {`{"foo": 12.0}`, ``, []ReadRuneTypeResult{
			{'{', 1, jsonparse.RuneTypeObjectBeg, nil},
			{'"', 1, jsonparse.RuneTypeStringBeg, nil},
			{'f', 1, jsonparse.RuneTypeStringChar, nil},
			{'o', 1, jsonparse.RuneTypeStringChar, nil},
			{'o', 1, jsonparse.RuneTypeStringChar, nil},
			{'"', 1, jsonparse.RuneTypeStringEnd, nil},
			{':', 1, jsonparse.RuneTypeObjectColon, nil},
			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{0, unreadRune, 0, nil},
			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{'2', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{'.', 1, jsonparse.RuneTypeNumberFracDot, nil},
			{'0', 1, jsonparse.RuneTypeNumberFracDig, nil},
			{'}', 1, jsonparse.RuneTypeObjectEnd, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
		}},
		"unread2": {`{"foo": 12.0}`, ``, []ReadRuneTypeResult{
			{'{', 1, jsonparse.RuneTypeObjectBeg, nil},
			{'"', 1, jsonparse.RuneTypeStringBeg, nil},
			{'f', 1, jsonparse.RuneTypeStringChar, nil},
			{'o', 1, jsonparse.RuneTypeStringChar, nil},
			{'o', 1, jsonparse.RuneTypeStringChar, nil},
			{'"', 1, jsonparse.RuneTypeStringEnd, nil},
			{':', 1, jsonparse.RuneTypeObjectColon, nil},
			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{0, unreadRune, 0, nil},
			{0, unreadRune, 0, ErrInvalidUnreadRune},
			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{'2', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{'.', 1, jsonparse.RuneTypeNumberFracDot, nil},
			{'0', 1, jsonparse.RuneTypeNumberFracDig, nil},
			{'}', 1, jsonparse.RuneTypeObjectEnd, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
		}},
		"unread-eof": {`[1,2]`, ``, []ReadRuneTypeResult{
			{'[', 1, jsonparse.RuneTypeArrayBeg, nil},
			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{',', 1, jsonparse.RuneTypeArrayComma, nil},
			{0, pushReadBarrier, 0, nil},
			{'2', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, unreadRune, 0, ErrInvalidUnreadRune},
			{0, popReadBarrier, 0, nil},
			{']', 1, jsonparse.RuneTypeArrayEnd, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, unreadRune, 0, ErrInvalidUnreadRune},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
		}},
		"tail-ws": {`{"foo": 12.0}  `, ``, []ReadRuneTypeResult{
			// Disable auto-child.
			{0, pushReadBarrier, 0, nil},
			{0, popReadBarrier, 0, nil},
			// Test main.
			{'{', 1, jsonparse.RuneTypeObjectBeg, nil},
			{'"', 1, jsonparse.RuneTypeStringBeg, nil},
			{'f', 1, jsonparse.RuneTypeStringChar, nil},
			{'o', 1, jsonparse.RuneTypeStringChar, nil},
			{'o', 1, jsonparse.RuneTypeStringChar, nil},
			{'"', 1, jsonparse.RuneTypeStringEnd, nil},
			{':', 1, jsonparse.RuneTypeObjectColon, nil},
			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{'2', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{'.', 1, jsonparse.RuneTypeNumberFracDot, nil},
			{'0', 1, jsonparse.RuneTypeNumberFracDig, nil},
			{'}', 1, jsonparse.RuneTypeObjectEnd, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
		}},
		"child-tail-ws": {`[1,` + `{"foo": 12.0}  `, `  `, []ReadRuneTypeResult{
			// Child prefix.
			{'[', 1, jsonparse.RuneTypeArrayBeg, nil},
			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{',', 1, jsonparse.RuneTypeArrayComma, nil},
			{0, pushReadBarrier, 0, nil},
			// Test main.
			{'{', 1, jsonparse.RuneTypeObjectBeg, nil},
			{'"', 1, jsonparse.RuneTypeStringBeg, nil},
			{'f', 1, jsonparse.RuneTypeStringChar, nil},
			{'o', 1, jsonparse.RuneTypeStringChar, nil},
			{'o', 1, jsonparse.RuneTypeStringChar, nil},
			{'"', 1, jsonparse.RuneTypeStringEnd, nil},
			{':', 1, jsonparse.RuneTypeObjectColon, nil},
			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{'2', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{'.', 1, jsonparse.RuneTypeNumberFracDot, nil},
			{'0', 1, jsonparse.RuneTypeNumberFracDig, nil},
			{'}', 1, jsonparse.RuneTypeObjectEnd, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
		}},
		"syntax-error": {`[[0,]`, ``, []ReadRuneTypeResult{
			{'[', 1, jsonparse.RuneTypeArrayBeg, nil},
			{'[', 1, jsonparse.RuneTypeArrayBeg, nil},
			{'0', 1, jsonparse.RuneTypeNumberIntZero, nil},
			{',', 1, jsonparse.RuneTypeArrayComma, nil},
			{']', 1, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 4, Err: fmt.Errorf("invalid character %q looking for beginning of value", ']')}},
			{']', 1, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 4, Err: fmt.Errorf("invalid character %q looking for beginning of value", ']')}},
			{']', 1, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 4, Err: fmt.Errorf("invalid character %q looking for beginning of value", ']')}},
		}},
		"multi-value1": {`1{}`, `{}`, []ReadRuneTypeResult{
			{0, pushReadBarrier, 0, nil},
			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, popReadBarrier, 0, nil},
		}},
		"multi-value2": {`1{}`, ``, []ReadRuneTypeResult{
			{0, pushReadBarrier, 0, nil},
			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, popReadBarrier, 0, nil},
			{0, reset, 0, nil},
			{0, pushReadBarrier, 0, nil},
			{'{', 1, jsonparse.RuneTypeObjectBeg, nil},
			{'}', 1, jsonparse.RuneTypeObjectEnd, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, popReadBarrier, 0, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
		}},
		"early-eof": {` {`, ``, []ReadRuneTypeResult{
			{'{', 1, jsonparse.RuneTypeObjectBeg, nil},
			{0, 0, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 2, Err: io.ErrUnexpectedEOF}},
			{0, 0, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 2, Err: io.ErrUnexpectedEOF}},
			{0, 0, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 2, Err: io.ErrUnexpectedEOF}},
		}},
		"empty": {``, ``, []ReadRuneTypeResult{
			{0, 0, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 0, Err: io.EOF}},
			{0, 0, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 0, Err: io.EOF}},
			{0, 0, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 0, Err: io.EOF}},
		}},
		"basic2": {`1`, ``, []ReadRuneTypeResult{
			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
		}},
		"fragment": {`1,`, ``, []ReadRuneTypeResult{
			// Disable auto-child.
			{0, pushReadBarrier, 0, nil},
			{0, popReadBarrier, 0, nil},
			// Test main.
			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{',', 1, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 1, Err: fmt.Errorf("invalid character %q after top-level value", ',')}},
			{',', 1, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 1, Err: fmt.Errorf("invalid character %q after top-level value", ',')}},
			{',', 1, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 1, Err: fmt.Errorf("invalid character %q after top-level value", ',')}},
		}},
		"child-fragment": {`[1,` + `1,`, `,`, []ReadRuneTypeResult{
			// Child prefix.
			{'[', 1, jsonparse.RuneTypeArrayBeg, nil},
			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{',', 1, jsonparse.RuneTypeArrayComma, nil},
			{0, pushReadBarrier, 0, nil},
			// Test main.
			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
		}},
		"elem": {` { "foo" : 12.0 } `, ``, []ReadRuneTypeResult{
			// Disable auto-child.
			{0, pushReadBarrier, 0, nil},
			{0, popReadBarrier, 0, nil},
			// Test main.
			{'{', 1, jsonparse.RuneTypeObjectBeg, nil},
			{'"', 1, jsonparse.RuneTypeStringBeg, nil},
			{'f', 1, jsonparse.RuneTypeStringChar, nil},
			{'o', 1, jsonparse.RuneTypeStringChar, nil},
			{'o', 1, jsonparse.RuneTypeStringChar, nil},
			{'"', 1, jsonparse.RuneTypeStringEnd, nil},
			{':', 1, jsonparse.RuneTypeObjectColon, nil},
			{0, pushReadBarrier, 0, nil},
			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{'2', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{'.', 1, jsonparse.RuneTypeNumberFracDot, nil},
			{'0', 1, jsonparse.RuneTypeNumberFracDig, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, popReadBarrier, 0, nil},
			{'}', 1, jsonparse.RuneTypeObjectEnd, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
		}},
		"child-elem": {`[1,` + ` { "foo" : 12.0 } `, ` `, []ReadRuneTypeResult{
			// Child prefix.
			{'[', 1, jsonparse.RuneTypeArrayBeg, nil},
			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{',', 1, jsonparse.RuneTypeArrayComma, nil},
			{0, pushReadBarrier, 0, nil},
			// Test main.
			{'{', 1, jsonparse.RuneTypeObjectBeg, nil},
			{'"', 1, jsonparse.RuneTypeStringBeg, nil},
			{'f', 1, jsonparse.RuneTypeStringChar, nil},
			{'o', 1, jsonparse.RuneTypeStringChar, nil},
			{'o', 1, jsonparse.RuneTypeStringChar, nil},
			{'"', 1, jsonparse.RuneTypeStringEnd, nil},
			{':', 1, jsonparse.RuneTypeObjectColon, nil},
			{0, pushReadBarrier, 0, nil},
			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{'2', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{'.', 1, jsonparse.RuneTypeNumberFracDot, nil},
			{'0', 1, jsonparse.RuneTypeNumberFracDig, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, popReadBarrier, 0, nil},
			{'}', 1, jsonparse.RuneTypeObjectEnd, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
		}},
		"invalid-number": {`1.2.3`, ``, []ReadRuneTypeResult{
			{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{'.', 1, jsonparse.RuneTypeNumberFracDot, nil},
			{'2', 1, jsonparse.RuneTypeNumberFracDig, nil},
			{'.', 1, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 3, Err: fmt.Errorf("invalid character %q after top-level value", '.')}},
			{0, reset, 0, nil},
			{'3', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
		}},
		"trailing-garbage": {" 42 x", ``, []ReadRuneTypeResult{
			{0, pushReadBarrier, 0, nil},
			{'4', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{0, unreadRune, 0, nil},
			{'4', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{0, unreadRune, 0, nil},
			{0, pushReadBarrier, 0, nil},
			{'4', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{'2', 1, jsonparse.RuneTypeNumberIntDig, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, popReadBarrier, 0, nil},
			{0, popReadBarrier, 0, nil},
			{'x', 1, jsonparse.RuneTypeError, &DecodeSyntaxError{Offset: 4, Err: fmt.Errorf("invalid character %q after top-level value", 'x')}},
		}},
		"unread-reset": {`{}`, ``, []ReadRuneTypeResult{
			{'{', 1, jsonparse.RuneTypeObjectBeg, nil},
			{0, unreadRune, 0, nil},
			{0, reset, 0, nil},
			{'{', 1, jsonparse.RuneTypeObjectBeg, nil},
			{'}', 1, jsonparse.RuneTypeObjectEnd, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
			{0, 0, jsonparse.RuneTypeEOF, nil},
		}},
	}
	func() {
		childTestcases := make(map[string]runeTypeScannerTestcase)
		for tcName, tc := range testcases {
			canChild := true
			for _, res := range tc.Exp {
				if res.s == pushReadBarrier || res.s == reset {
					canChild = false
					break
				}
			}
			if !canChild {
				continue
			}
			tc.Input = `[1,` + tc.Input
			tc.Exp = append([]ReadRuneTypeResult{
				{'[', 1, jsonparse.RuneTypeArrayBeg, nil},
				{'1', 1, jsonparse.RuneTypeNumberIntDig, nil},
				{',', 1, jsonparse.RuneTypeArrayComma, nil},
				{0, pushReadBarrier, 0, nil},
			}, tc.Exp...)
			for i := 2; i < len(tc.Exp); i++ {
				if se, ok := tc.Exp[i].e.(*DecodeSyntaxError); ok {
					seCopy := *se
					seCopy.Offset += 3
					tc.Exp[i].e = &seCopy
				}
			}
			childTestcases["child-"+tcName] = tc
		}
		for tcName, tc := range childTestcases {
			testcases[tcName] = tc
		}
	}()
	for tcName, tc := range testcases {
		tc := tc
		t.Run(tcName, func(t *testing.T) {
			t.Parallel()
			t.Logf("input=%q", tc.Input)
			reader := strings.NewReader(tc.Input)
			sc := &runeTypeScanner{inner: reader}
			var exp, act []string
			for _, iExp := range tc.Exp {
				var iAct ReadRuneTypeResult
				switch iExp.s {
				case unreadRune:
					iAct.s = iExp.s
					iAct.e = sc.UnreadRune()
				case pushReadBarrier:
					sc.PushReadBarrier()
					iAct.s = iExp.s
				case popReadBarrier:
					sc.PopReadBarrier()
					iAct.s = iExp.s
				case reset:
					sc.Reset()
					iAct.s = iExp.s
				default:
					iAct.r, iAct.s, iAct.t, iAct.e = sc.ReadRuneType()
				}
				exp = append(exp, iExp.String())
				act = append(act, iAct.String())
			}
			assert.Equal(t, exp, act)
			assert.Equal(t, tc.ExpRemainder, tc.Input[len(tc.Input)-reader.Len():])
		})
	}
}