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

// Package jsonutil provides utilities for implementing the interfaces
// consumed by the "git.lukeshu.com/go/lowmemjson" package.
package jsonutil

import (
	"io"

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

func EncodeHexString[T ~[]byte | ~string](w io.Writer, str T) error {
	const hextable = "0123456789abcdef"
	var buf [2]byte
	buf[0] = '"'
	if _, err := w.Write(buf[:1]); err != nil {
		return err
	}
	for i := 0; i < len(str); i++ {
		buf[0] = hextable[str[i]>>4]
		buf[1] = hextable[str[i]&0x0f]
		if _, err := w.Write(buf[:]); err != nil {
			return err
		}
	}
	buf[0] = '"'
	if _, err := w.Write(buf[:1]); err != nil {
		return err
	}
	return nil
}

func DecodeHexString(r io.RuneScanner, dst io.ByteWriter) error {
	dec := &hexDecoder{dst: dst}
	if err := lowmemjson.DecodeString(r, dec); err != nil {
		return err
	}
	return dec.Close()
}

func EncodeSplitHexString[T ~[]byte | ~string](w io.Writer, str T, maxStrLen int) error {
	if maxStrLen <= 0 || len(str) <= maxStrLen/2 {
		return EncodeHexString(w, str)
	}
	var buf [1]byte
	buf[0] = '['
	if _, err := w.Write(buf[:]); err != nil {
		return err
	}
	for len(str) > maxStrLen/2 {
		if err := EncodeHexString(w, str[:maxStrLen/2]); err != nil {
			return err
		}
		str = str[maxStrLen/2:]
		if len(str) > 0 {
			buf[0] = ','
			if _, err := w.Write(buf[:]); err != nil {
				return err
			}
		}
	}
	if len(str) > 0 {
		if err := EncodeHexString(w, str); err != nil {
			return err
		}
	}
	buf[0] = ']'
	if _, err := w.Write(buf[:]); err != nil {
		return err
	}
	return nil
}

func DecodeSplitHexString(r io.RuneScanner, dst io.ByteWriter) error {
	c, _, _ := r.ReadRune()
	_ = r.UnreadRune()
	if c == '"' {
		return DecodeHexString(r, dst)
	}
	return lowmemjson.DecodeArray(r, func(r io.RuneScanner) error {
		return DecodeHexString(r, dst)
	})
}