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

package json_test

import (
	"bytes"
	std "encoding/json"
	"errors"
	"io"
	"strconv"
	"strings"
	"testing"
	"unicode/utf8"

	"github.com/stretchr/testify/assert"

	low "git.lukeshu.com/go/lowmemjson/compat/json"
)

func assertEquivErr(t *testing.T, stdErr, lowErr error) {
	if (stdErr == nil) || (lowErr == nil) {
		// Nil-equal.
		assert.Equal(t, stdErr, lowErr)
		return
	}
	switch stdErr.(type) {
	case *std.SyntaxError:
		if lowErr != nil {
			stdMsg := stdErr.Error()
			lowMsg := lowErr.Error()

			// https://github.com/golang/go/issues/58680
			if strings.HasPrefix(stdMsg, `invalid character ' ' `) &&
				(errors.Is(lowErr, io.ErrUnexpectedEOF) || lowMsg == "unexpected end of JSON input") {
				return
			}

			// https://github.com/golang/go/issues/58713
			prefix := `invalid character '`
			if stdMsg != lowMsg && strings.HasPrefix(stdMsg, prefix) && strings.HasPrefix(lowMsg, prefix) {
				stdRune, stdRuneSize := utf8.DecodeRuneInString(stdMsg[len(prefix):])
				lowByte := lowMsg[len(prefix)]
				if lowByte == '\\' {
					switch lowMsg[len(prefix)+1] {
					case 'a':
						lowByte = '\a'
					case 'b':
						lowByte = '\b'
					case 'f':
						lowByte = '\f'
					case 'n':
						lowByte = '\n'
					case 'r':
						lowByte = '\r'
					case 't':
						lowByte = '\t'
					case 'v':
						lowByte = '\v'
					case '\\', '\'':
						lowByte = lowMsg[len(prefix)+1]
					case 'x':
						lowByte64, _ := strconv.ParseUint(lowMsg[len(prefix)+2:][:2], 16, 8)
						lowByte = byte(lowByte64)
					case 'u':
						lowRune, _ := strconv.ParseUint(lowMsg[len(prefix)+2:][:4], 16, 16)
						var buf [4]byte
						utf8.EncodeRune(buf[:], rune(lowRune))
						lowByte = buf[0]
					case 'U':
						lowRune, _ := strconv.ParseUint(lowMsg[len(prefix)+2:][:8], 16, 32)
						var buf [4]byte
						utf8.EncodeRune(buf[:], rune(lowRune))
						lowByte = buf[0]
					}
				}
				if stdRune == rune(lowByte) {
					lowRuneStr := lowMsg[len(prefix):]
					lowRuneStr = lowRuneStr[:strings.IndexByte(lowRuneStr, '\'')]
					stdMsg = prefix + lowRuneStr + stdMsg[len(prefix)+stdRuneSize:]
					stdErr = errors.New(stdMsg)
				}
			}

			// I'd file a ticket for this, but @dsnet (one of the encoding/json maintainers) says that he's
			// working on a parser-rewrite that would fix a bunch of this type of issue.
			// https://github.com/golang/go/issues/58680#issuecomment-1444224084
			if strings.HasPrefix(stdMsg, `invalid character '\u00`) && strings.HasPrefix(lowMsg, `invalid character '\x`) {
				stdMsg = `invalid character '\x` + strings.TrimPrefix(stdMsg, `invalid character '\u00`)
				stdErr = errors.New(stdMsg)
			}
		}
		// Text-equal.
		assert.Equal(t, stdErr.Error(), lowErr.Error())
		// TODO: Assert that they are deep-equal (but be permissive of these not being type aliases).
	case *std.MarshalerError:
		// Text-equal.
		assert.Equal(t, stdErr.Error(), lowErr.Error())
		// TODO: Assert that they are deep-equal (but be permissive of these not being type aliases).
	default:
		// Text-equal.
		assert.Equal(t, stdErr.Error(), lowErr.Error())
		// TODO: Assert that they are deep-equal.
	}
}

func FuzzEquiv(f *testing.F) {
	f.Fuzz(func(t *testing.T, str []byte) {
		t.Logf("str=%q", str)
		t.Run("HTMLEscape", func(t *testing.T) {
			var stdOut bytes.Buffer
			std.HTMLEscape(&stdOut, str)

			var lowOut bytes.Buffer
			low.HTMLEscape(&lowOut, str)

			assert.Equal(t, stdOut.String(), lowOut.String())
		})
		t.Run("Compact", func(t *testing.T) {
			var stdOut bytes.Buffer
			stdErr := std.Compact(&stdOut, str)

			var lowOut bytes.Buffer
			lowErr := low.Compact(&lowOut, str)

			assert.Equal(t, stdOut.String(), lowOut.String())
			assertEquivErr(t, stdErr, lowErr)
		})
		t.Run("Indent", func(t *testing.T) {
			var stdOut bytes.Buffer
			stdErr := std.Indent(&stdOut, str, "»", "\t")

			var lowOut bytes.Buffer
			lowErr := low.Indent(&lowOut, str, "»", "\t")

			assert.Equal(t, stdOut.String(), lowOut.String())
			assertEquivErr(t, stdErr, lowErr)
		})
		t.Run("Valid", func(t *testing.T) {
			stdValid := std.Valid(str) && utf8.Valid(str) // https://github.com/golang/go/issues/58517
			lowValid := low.Valid(str)
			assert.Equal(t, stdValid, lowValid)
		})
		t.Run("Decode-Encode", func(t *testing.T) {
			var stdObj any
			stdErr := std.NewDecoder(bytes.NewReader(str)).Decode(&stdObj)

			var lowObj any
			lowErr := low.NewDecoder(bytes.NewReader(str)).Decode(&lowObj)

			assert.Equal(t, stdObj, lowObj)
			assertEquivErr(t, stdErr, lowErr)
			if t.Failed() {
				return
			}

			var stdOut bytes.Buffer
			stdErr = std.NewEncoder(&stdOut).Encode(stdObj)

			var lowOut bytes.Buffer
			lowErr = low.NewEncoder(&lowOut).Encode(lowObj)

			assert.Equal(t, stdOut.String(), lowOut.String())
			assertEquivErr(t, stdErr, lowErr)
		})
		t.Run("Unmarshal-Marshal", func(t *testing.T) {
			var stdObj any
			stdErr := std.Unmarshal(str, &stdObj)

			var lowObj any
			lowErr := low.Unmarshal(str, &lowObj)

			assert.Equal(t, stdObj, lowObj)
			assertEquivErr(t, stdErr, lowErr)
			if t.Failed() {
				return
			}

			stdOut, stdErr := std.Marshal(stdObj)
			lowOut, lowErr := low.Marshal(lowObj)

			assert.Equal(t, string(stdOut), string(lowOut))
			assertEquivErr(t, stdErr, lowErr)
		})
	})
}