// 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 reEncodeIndent struct {
	out reEncoderModule

	// String to use to indent.
	//
	// Newlines are emitted *between* top-level values; a newline
	// is not emitted after the *last* top-level value.
	Indent string

	// String to put before indents.
	Prefix string

	// state
	lastNonSpace       jsonparse.RuneType
	lastNonSpaceNonEOF jsonparse.RuneType
	curIndent          int
}

var _ reEncoderModule = (*reEncodeIndent)(nil)

func (enc *reEncodeIndent) PopWriteBarrier() {
	enc.lastNonSpace = enc.lastNonSpaceNonEOF
	enc.out.PopWriteBarrier()
}

func (enc *reEncodeIndent) HandleRune(c rune, t jsonparse.RuneType, escape BackslashEscapeMode, stackSize int) error {
	// emit newlines between top-level values
	if enc.lastNonSpace == jsonparse.RuneTypeEOF && t != jsonparse.RuneTypeSpace {
		if err := enc.out.HandleRune('\n', jsonparse.RuneTypeSpace, 0, 0); err != nil {
			return err
		}
	}

	// indent
	switch t {
	case jsonparse.RuneTypeSpace:
		// let us manage whitespace, don't pass it through
		return nil
	case jsonparse.RuneTypeObjectEnd, jsonparse.RuneTypeArrayEnd:
		enc.curIndent--
		switch enc.lastNonSpace {
		case jsonparse.RuneTypeObjectBeg, jsonparse.RuneTypeArrayBeg:
			// collapse
		default:
			if err := enc.emitNlIndent(stackSize + 1); err != nil {
				return err
			}
		}
	default:
		switch enc.lastNonSpace {
		case jsonparse.RuneTypeObjectBeg, jsonparse.RuneTypeObjectComma, jsonparse.RuneTypeArrayBeg, jsonparse.RuneTypeArrayComma:
			if err := enc.emitNlIndent(stackSize); err != nil {
				return err
			}
		case jsonparse.RuneTypeObjectColon:
			if err := enc.out.HandleRune(' ', jsonparse.RuneTypeSpace, 0, stackSize); err != nil {
				return err
			}
		}
		switch t {
		case jsonparse.RuneTypeObjectBeg, jsonparse.RuneTypeArrayBeg:
			enc.curIndent++
		}
	}

	if t != jsonparse.RuneTypeSpace {
		enc.lastNonSpace = t
		if t != jsonparse.RuneTypeEOF {
			enc.lastNonSpaceNonEOF = t
		}
	}
	return enc.out.HandleRune(c, t, escape, stackSize)
}

func (enc *reEncodeIndent) emitNlIndent(stackSize int) error {
	if err := enc.out.HandleRune('\n', jsonparse.RuneTypeSpace, 0, stackSize); err != nil {
		return err
	}
	for _, c := range enc.Prefix {
		if err := enc.out.HandleRune(c, jsonparse.RuneTypeSpace, 0, stackSize); err != nil {
			return err
		}
	}
	for i := 0; i < enc.curIndent; i++ {
		for _, c := range enc.Indent {
			if err := enc.out.HandleRune(c, jsonparse.RuneTypeSpace, 0, stackSize); err != nil {
				return err
			}
		}
	}
	return nil
}