// Copyright 2015 The Gogs Authors. All rights reserved.
// Copyright 2019 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package git

import (
	"bufio"
	"bytes"
	"encoding/base64"
	"io"

	"code.gitea.io/gitea/modules/log"
	"code.gitea.io/gitea/modules/typesniffer"
	"code.gitea.io/gitea/modules/util"
)

// Blob represents a Git object.
type Blob struct {
	ID ObjectID

	gotSize bool
	size    int64
	name    string
	repo    *Repository
}

// DataAsync gets a ReadCloser for the contents of a blob without reading it all.
// Calling the Close function on the result will discard all unread output.
func (b *Blob) DataAsync() (io.ReadCloser, error) {
	wr, rd, cancel, err := b.repo.CatFileBatch(b.repo.Ctx)
	if err != nil {
		return nil, err
	}

	_, err = wr.Write([]byte(b.ID.String() + "\n"))
	if err != nil {
		cancel()
		return nil, err
	}
	_, _, size, err := ReadBatchLine(rd)
	if err != nil {
		cancel()
		return nil, err
	}
	b.gotSize = true
	b.size = size

	if size < 4096 {
		bs, err := io.ReadAll(io.LimitReader(rd, size))
		defer cancel()
		if err != nil {
			return nil, err
		}
		_, err = rd.Discard(1)
		return io.NopCloser(bytes.NewReader(bs)), err
	}

	return &blobReader{
		rd:     rd,
		n:      size,
		cancel: cancel,
	}, nil
}

// Size returns the uncompressed size of the blob
func (b *Blob) Size() int64 {
	if b.gotSize {
		return b.size
	}

	wr, rd, cancel, err := b.repo.CatFileBatchCheck(b.repo.Ctx)
	if err != nil {
		log.Debug("error whilst reading size for %s in %s. Error: %v", b.ID.String(), b.repo.Path, err)
		return 0
	}
	defer cancel()
	_, err = wr.Write([]byte(b.ID.String() + "\n"))
	if err != nil {
		log.Debug("error whilst reading size for %s in %s. Error: %v", b.ID.String(), b.repo.Path, err)
		return 0
	}
	_, _, b.size, err = ReadBatchLine(rd)
	if err != nil {
		log.Debug("error whilst reading size for %s in %s. Error: %v", b.ID.String(), b.repo.Path, err)
		return 0
	}

	b.gotSize = true

	return b.size
}

type blobReader struct {
	rd     *bufio.Reader
	n      int64
	cancel func()
}

func (b *blobReader) Read(p []byte) (n int, err error) {
	if b.n <= 0 {
		return 0, io.EOF
	}
	if int64(len(p)) > b.n {
		p = p[0:b.n]
	}
	n, err = b.rd.Read(p)
	b.n -= int64(n)
	return n, err
}

// Close implements io.Closer
func (b *blobReader) Close() error {
	if b.rd == nil {
		return nil
	}

	defer b.cancel()

	if err := DiscardFull(b.rd, b.n+1); err != nil {
		return err
	}

	b.rd = nil

	return nil
}

// Name returns name of the tree entry this blob object was created from (or empty string)
func (b *Blob) Name() string {
	return b.name
}

// GetBlobContent Gets the limited content of the blob as raw text
func (b *Blob) GetBlobContent(limit int64) (string, error) {
	if limit <= 0 {
		return "", nil
	}
	dataRc, err := b.DataAsync()
	if err != nil {
		return "", err
	}
	defer dataRc.Close()
	buf, err := util.ReadWithLimit(dataRc, int(limit))
	return string(buf), err
}

// GetBlobLineCount gets line count of the blob
func (b *Blob) GetBlobLineCount() (int, error) {
	reader, err := b.DataAsync()
	if err != nil {
		return 0, err
	}
	defer reader.Close()
	buf := make([]byte, 32*1024)
	count := 1
	lineSep := []byte{'\n'}

	c, err := reader.Read(buf)
	if c == 0 && err == io.EOF {
		return 0, nil
	}
	for {
		count += bytes.Count(buf[:c], lineSep)
		switch {
		case err == io.EOF:
			return count, nil
		case err != nil:
			return count, err
		}
		c, err = reader.Read(buf)
	}
}

// GetBlobContentBase64 Reads the content of the blob with a base64 encode and returns the encoded string
func (b *Blob) GetBlobContentBase64() (string, error) {
	dataRc, err := b.DataAsync()
	if err != nil {
		return "", err
	}
	defer dataRc.Close()

	pr, pw := io.Pipe()
	encoder := base64.NewEncoder(base64.StdEncoding, pw)

	go func() {
		_, err := io.Copy(encoder, dataRc)
		_ = encoder.Close()

		if err != nil {
			_ = pw.CloseWithError(err)
		} else {
			_ = pw.Close()
		}
	}()

	out, err := io.ReadAll(pr)
	if err != nil {
		return "", err
	}
	return string(out), nil
}

// GuessContentType guesses the content type of the blob.
func (b *Blob) GuessContentType() (typesniffer.SniffedType, error) {
	r, err := b.DataAsync()
	if err != nil {
		return typesniffer.SniffedType{}, err
	}
	defer r.Close()

	return typesniffer.DetectContentTypeFromReader(r)
}

// GetBlob finds the blob object in the repository.
func (repo *Repository) GetBlob(idStr string) (*Blob, error) {
	id, err := NewIDFromString(idStr)
	if err != nil {
		return nil, err
	}
	if id.IsZero() {
		return nil, ErrNotExist{id.String(), ""}
	}
	return &Blob{
		ID:   id,
		repo: repo,
	}, nil
}
