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

package lowmemjson

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

type reEncodeCompactNum struct {
	out reEncoderModule

	// state
	fracFirst bool
	fracZeros int64
	expZero   bool
}

var _ reEncoderModule = (*reEncodeCompactNum)(nil)

func (enc *reEncodeCompactNum) PopWriteBarrier() {
	enc.out.PopWriteBarrier()
}

func (enc *reEncodeCompactNum) HandleRune(c rune, t jsonparse.RuneType, escape BackslashEscapeMode, stackSize int) error {
	// trim trailing '0's from the fraction-part, but don't remove all digits
	switch t {
	case jsonparse.RuneTypeNumberFracDot:
		enc.fracFirst = true
		enc.fracZeros = 0
	case jsonparse.RuneTypeNumberFracDig:
		if c == '0' && !enc.fracFirst {
			enc.fracZeros++
			return nil
		} else {
			for ; enc.fracZeros > 0; enc.fracZeros-- {
				if err := enc.out.HandleRune('0', jsonparse.RuneTypeNumberFracDig, escape, stackSize); err != nil {
					return err
				}
			}
		}
		enc.fracFirst = false
	}

	// trim leading '0's from the exponent-part, but don't remove all digits
	switch t {
	case jsonparse.RuneTypeNumberExpE, jsonparse.RuneTypeNumberExpSign:
		enc.expZero = true
	case jsonparse.RuneTypeNumberExpDig:
		if c == '0' && enc.expZero {
			return nil
		}
		enc.expZero = false
	default:
		if enc.expZero {
			if err := enc.out.HandleRune('0', jsonparse.RuneTypeNumberFracDig, escape, stackSize); err != nil {
				return err
			}
			enc.expZero = false
		}
	}

	return enc.out.HandleRune(c, t, escape, stackSize)
}