// Copyright 2022 Harness Inc. All rights reserved.
// Use of this source code is governed by the Polyform Free Trial License
// that can be found in the LICENSE.md file for this repository.

package service

import (
	"bytes"
	"context"
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"

	"github.com/harness/gitness/gitrpc/internal/types"
	"github.com/harness/gitness/gitrpc/rpc"
	"github.com/rs/zerolog/log"
	"google.golang.org/grpc/codes"
	"google.golang.org/grpc/status"
)

const (
	maxFileSize    = 1 << 20
	repoSubdirName = "repos"
	gitRepoSuffix  = "git"

	gitReferenceNamePrefixBranch = "refs/heads/"
	gitReferenceNamePrefixTag    = "refs/tags/"
)

var (
	// TODO: Should be matching the sytem identity from config.
	SystemIdentity = &rpc.Identity{
		Name:  "gitness",
		Email: "system@gitness",
	}
)

type Storage interface {
	Save(filePath string, data bytes.Buffer) (string, error)
}

type RepositoryService struct {
	rpc.UnimplementedRepositoryServiceServer
	adapter   GitAdapter
	store     Storage
	reposRoot string
}

func NewRepositoryService(adapter GitAdapter, store Storage, gitRoot string) (*RepositoryService, error) {
	reposRoot := filepath.Join(gitRoot, repoSubdirName)
	if _, err := os.Stat(reposRoot); errors.Is(err, os.ErrNotExist) {
		if err = os.MkdirAll(reposRoot, 0o700); err != nil {
			return nil, err
		}
	}

	return &RepositoryService{
		adapter:   adapter,
		store:     store,
		reposRoot: reposRoot,
	}, nil
}

func (s RepositoryService) getFullPathForRepo(uid string) string {
	// split repos into subfolders using their prefix to distribute repos accross a set of folders.
	return filepath.Join(
		s.reposRoot, // root folder
		uid[0:2],    // first subfolder
		uid[2:4],    // second subfolder
		fmt.Sprintf("%s.%s", uid[4:], gitRepoSuffix), // remainder with .git
	)
}

//nolint:gocognit // need to refactor this code
func (s RepositoryService) CreateRepository(stream rpc.RepositoryService_CreateRepositoryServer) error {
	// first get repo params from stream
	req, err := stream.Recv()
	if err != nil {
		return status.Errorf(codes.Internal, "cannot receive create repository data")
	}

	header := req.GetHeader()
	if header == nil {
		return status.Errorf(codes.Internal, "expected header to be first message in stream")
	}
	log.Info().Msgf("received a create repository request %v", header)

	repoPath := s.getFullPathForRepo(header.GetUid())
	if _, err = os.Stat(repoPath); !os.IsNotExist(err) {
		return status.Errorf(codes.AlreadyExists, "repository exists already: %v", repoPath)
	}

	// create repository in repos folder
	ctx, cancel := context.WithCancel(context.Background())
	defer cancel()
	err = s.adapter.InitRepository(ctx, repoPath, true)
	if err != nil {
		// on error cleanup repo dir
		defer func(path string) {
			_ = os.RemoveAll(path)
		}(repoPath)
		return fmt.Errorf("CreateRepository error: %w", err)
	}

	// update default branch (currently set to non-existent branch)
	err = s.adapter.SetDefaultBranch(ctx, repoPath, header.GetDefaultBranch(), true)
	if err != nil {
		return fmt.Errorf("error updating default branch for repo %s: %w", header.GetUid(), err)
	}

	// we need temp dir for cloning
	tempDir, err := os.MkdirTemp("", "*-"+header.GetUid())
	if err != nil {
		return fmt.Errorf("error creating temp dir for repo %s: %w", header.GetUid(), err)
	}
	defer func(path string) {
		// when repo is successfully created remove temp dir
		err2 := os.RemoveAll(path)
		if err2 != nil {
			log.Err(err2).Msg("failed to cleanup temporary dir.")
		}
	}(tempDir)

	// Clone repository to temp dir
	if err = s.adapter.Clone(ctx, repoPath, tempDir, types.CloneRepoOptions{}); err != nil {
		return status.Errorf(codes.Internal, "failed to clone repo: %v", err)
	}

	// logic for receiving files
	filePaths := make([]string, 0, 16)
	for {
		var filePath string
		filePath, err = s.handleFileUploadIfAvailable(tempDir, func() (*rpc.FileUpload, error) {
			m, err2 := stream.Recv()
			if err2 != nil {
				return nil, err2
			}
			return m.GetFile(), nil
		})
		if errors.Is(err, io.EOF) {
			log.Info().Msg("received stream EOF")
			break
		}
		if err != nil {
			return status.Errorf(codes.Internal, "failed to receive file: %v", err)
		}

		filePaths = append(filePaths, filePath)
	}

	if len(filePaths) > 0 {
		// NOTE: This creates the branch in origin repo (as it doesn't exist as of now)
		// TODO: this should at least be a constant and not hardcoded?
		if err = s.AddFilesAndPush(ctx, tempDir, filePaths, "HEAD:"+header.GetDefaultBranch(), SystemIdentity, SystemIdentity,
			"origin", "initial commit"); err != nil {
			return err
		}
	}

	res := &rpc.CreateRepositoryResponse{}
	err = stream.SendAndClose(res)
	if err != nil {
		return status.Errorf(codes.Internal, "cannot send completion response: %v", err)
	}

	log.Info().Msgf("repository created. Path: %s", repoPath)
	return nil
}