package gopp

import (
	"bytes"
	"context"
	"io"
)

type Parsed struct {
	Texts [][]byte
	PreCode []byte
	Codes [][]byte
}

type Preprocessor struct {
	xgo *XGo
	tags [2][]byte
	preTag byte
}

// Get the new preprocessor with default options.
func New(xgo *XGo) *Preprocessor {
	pp := &Preprocessor{}
	pp.xgo = xgo
	pp.tags = [2][]byte{
		[]byte("{{"),
		[]byte("}}"),
	}
	pp.preTag = '#'
	return pp
}

func (pp *Preprocessor) XGo() *XGo {
	return pp.xgo
}

func (pp *Preprocessor) Parse(
	ctx context.Context,
	input io.Reader,
) (*Parsed, error) {
	data, err := io.ReadAll(input)
	if err != nil {
		return nil, err
	}
	//var b bytes.Buffer
	preCode := []byte(nil)
	texts := [][]byte{}
	codes := [][]byte{}
	pref := append(pp.tags[0], pp.preTag)
	if bytes.HasPrefix(data, pref) {
		idxEnd := bytes.Index(data, pp.tags[1])
		if idxEnd < 0 {
			return nil, UnexpectedError{
				What: "pre-code start tag",
			}
		}
		preCode = data[len(pref):idxEnd]
		//texts = append(texts, []byte{})
		data = data[idxEnd+len(pp.tags[1]):]
	}
	for {
		idxStart := bytes.Index(data, pp.tags[0])
		idxEnd := bytes.Index(data, pp.tags[1])
		//fmt.Printf("cock %d %d %d\n", last, idxStart, idxEnd)
		if idxStart < 0 {
			if idxEnd >= 0 {
				return nil, UnexpectedError{
					What: "end tag",
				}
			}
			texts = append(texts, data)
			break
		} else if idxEnd < 0 {
			return nil, UnexpectedError{
				What: "start tag",
			}
		}

		text := data[:idxStart]
		texts = append(texts, text)

		code := data[idxStart+len(pp.tags[0]):idxEnd]
		codes = append(codes, code)

		data = data[idxEnd + len(pp.tags[1]):]
	}

	return &Parsed{
		Texts: texts,
		PreCode: preCode,
		Codes: codes,
	}, nil
}

func (pp *Preprocessor) Render(
	ctx context.Context,
	input io.Reader,
	output io.Writer,
) error {
	parsed, err := pp.Parse(ctx, input)
	if err != nil { return err }

	return pp.xgo.Render(ctx, parsed, output)
}

func (pp *Preprocessor) Compile(
	ctx context.Context,
	input io.Reader,
) (*Compiled, error) {
	parsed, err := pp.Parse(ctx, input)
	if err != nil {
		return nil, err
	}

	compiled, err := pp.xgo.Compile(
		ctx,
		parsed,
	)
	if err != nil {
		return nil, err
	}

	return compiled, nil
}