// Copyright 2019 The Gitea Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.

package repofiles

import (
	"fmt"

	"code.gitea.io/gitea/models"
	"code.gitea.io/gitea/modules/git"
	"code.gitea.io/gitea/modules/setting"
	api "code.gitea.io/gitea/modules/structs"
)

// GetTreeBySHA get the GitTreeResponse of a repository using a sha hash.
func GetTreeBySHA(repo *models.Repository, sha string, page, perPage int, recursive bool) (*api.GitTreeResponse, error) {
	gitRepo, err := git.OpenRepository(repo.RepoPath())
	if err != nil {
		return nil, err
	}
	gitTree, err := gitRepo.GetTree(sha)
	if err != nil || gitTree == nil {
		return nil, models.ErrSHANotFound{
			SHA: sha,
		}
	}
	tree := new(api.GitTreeResponse)
	tree.SHA = gitTree.ResolvedID.String()
	tree.URL = repo.APIURL() + "/git/trees/" + tree.SHA
	var entries git.Entries
	if recursive {
		entries, err = gitTree.ListEntriesRecursive()
	} else {
		entries, err = gitTree.ListEntries()
	}
	if err != nil {
		return nil, err
	}
	apiURL := repo.APIURL()
	apiURLLen := len(apiURL)

	// 51 is len(sha1) + len("/git/blobs/"). 40 + 11.
	blobURL := make([]byte, apiURLLen+51)
	copy(blobURL, apiURL)
	copy(blobURL[apiURLLen:], "/git/blobs/")

	// 51 is len(sha1) + len("/git/trees/"). 40 + 11.
	treeURL := make([]byte, apiURLLen+51)
	copy(treeURL, apiURL)
	copy(treeURL[apiURLLen:], "/git/trees/")

	// 40 is the size of the sha1 hash in hexadecimal format.
	copyPos := len(treeURL) - 40

	if perPage <= 0 || perPage > setting.API.DefaultGitTreesPerPage {
		perPage = setting.API.DefaultGitTreesPerPage
	}
	if page <= 0 {
		page = 1
	}
	tree.Page = page
	tree.TotalCount = len(entries)
	rangeStart := perPage * (page - 1)
	if rangeStart >= len(entries) {
		return tree, nil
	}
	var rangeEnd int
	if len(entries) > perPage {
		tree.Truncated = true
	}
	if rangeStart+perPage < len(entries) {
		rangeEnd = rangeStart + perPage
	} else {
		rangeEnd = len(entries)
	}
	tree.Entries = make([]api.GitEntry, rangeEnd-rangeStart)
	for e := rangeStart; e < rangeEnd; e++ {
		i := e - rangeStart

		tree.Entries[e].Path = entries[e].Name()
		tree.Entries[e].Mode = fmt.Sprintf("%06o", entries[e].Mode())
		tree.Entries[e].Type = entries[e].Type()
		tree.Entries[e].Size = entries[e].Size()
		tree.Entries[e].SHA = entries[e].ID.String()

		if entries[e].IsDir() {
			copy(treeURL[copyPos:], entries[e].ID.String())
			tree.Entries[i].URL = string(treeURL)
		} else {
			copy(blobURL[copyPos:], entries[e].ID.String())
			tree.Entries[i].URL = string(blobURL)
		}
	}
	return tree, nil
}
