// Copyright 2018 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package git

import (
	"bufio"
	"context"
	"io"
	"strings"

	"gitea.dev/modules/git/gitcmd"
	"gitea.dev/modules/setting"
	"gitea.dev/modules/util"
)

// GetRefs returns all references of the repository.
func (repo *Repository) GetRefs(ctx context.Context) ([]*Reference, error) {
	return repo.GetRefsFiltered(ctx, "")
}

// ListOccurrences lists all refs of the given refType the given commit appears in sorted by creation date DESC
// refType should only be a literal "branch" or "tag" and nothing else
func (repo *Repository) ListOccurrences(ctx context.Context, refType, commitSHA string) ([]string, error) {
	cmd := gitcmd.NewCommand()
	switch refType {
	case "branch":
		cmd.AddArguments("branch")
	case "tag":
		cmd.AddArguments("tag")
	default:
		return nil, util.NewInvalidArgumentErrorf(`can only use "branch" or "tag" for refType, but got %q`, refType)
	}
	stdout, _, err := cmd.AddArguments("--no-color", "--sort=-creatordate", "--contains").
		AddDynamicArguments(commitSHA).WithRepo(repo).RunStdString(ctx)
	if err != nil {
		return nil, err
	}

	refs := strings.Split(strings.TrimSpace(stdout), "\n")
	if refType == "branch" {
		return parseBranches(refs), nil
	}
	return parseTags(refs), nil
}

func parseBranches(refs []string) []string {
	results := make([]string, 0, len(refs))
	for _, ref := range refs {
		if strings.HasPrefix(ref, "* ") { // current branch (main branch)
			results = append(results, ref[len("* "):])
		} else if strings.HasPrefix(ref, "  ") { // all other branches
			results = append(results, ref[len("  "):])
		} else if ref != "" {
			results = append(results, ref)
		}
	}
	return results
}

func parseTags(refs []string) []string {
	results := make([]string, 0, len(refs))
	for _, ref := range refs {
		if ref != "" {
			results = append(results, ref)
		}
	}
	return results
}

// UnstableGuessRefByShortName does the best guess to see whether a "short name" provided by user is a branch, tag or commit.
// It could guess wrongly if the input is already ambiguous. For example:
// * "refs/heads/the-name" vs "refs/heads/refs/heads/the-name"
// * "refs/tags/1234567890" vs commit "1234567890"
// In most cases, it SHOULD AVOID using this function, unless there is an irresistible reason (eg: make API friendly to end users)
// If the function is used, the caller SHOULD CHECK the ref type carefully.
func (repo *Repository) UnstableGuessRefByShortName(ctx context.Context, shortName string) RefName {
	if repo.IsBranchExist(ctx, shortName) {
		return RefNameFromBranch(shortName)
	}
	if repo.IsTagExist(ctx, shortName) {
		return RefNameFromTag(shortName)
	}
	if strings.HasPrefix(shortName, "refs/") {
		if repo.IsReferenceExist(ctx, shortName) {
			return RefName(shortName)
		}
	}
	commit, err := repo.GetCommit(ctx, shortName)
	if err == nil {
		commitIDString := commit.ID.String()
		// make sure the "shortName" is either partial commit ID, or it is HEAD
		if strings.HasPrefix(commitIDString, shortName) || shortName == RefNameHead {
			return RefName(commitIDString)
		} else {
			setting.PanicInDevOrTesting("abuse of UnstableGuessRefByShortName, queried %s, got %s", shortName, commitIDString)
		}
	}
	return ""
}

// GetRefsFiltered returns all references of the repository that matches patterm exactly or starting with.
func (repo *Repository) GetRefsFiltered(ctx context.Context, pattern string) ([]*Reference, error) {
	refs := make([]*Reference, 0)
	cmd := gitcmd.NewCommand("for-each-ref")
	stdoutReader, stdoutReaderClose := cmd.MakeStdoutPipe()
	defer stdoutReaderClose()
	err := cmd.WithRepo(repo).
		WithPipelineFunc(func(context gitcmd.Context) error {
			bufReader := bufio.NewReader(stdoutReader)
			for {
				// The output of for-each-ref is simply a list:
				// <sha> SP <type> TAB <ref> LF
				sha, err := bufReader.ReadString(' ')
				if err == io.EOF {
					break
				}
				if err != nil {
					return err
				}
				sha = sha[:len(sha)-1]

				typ, err := bufReader.ReadString('\t')
				if err == io.EOF {
					// This should not happen, but we'll tolerate it
					break
				}
				if err != nil {
					return err
				}
				typ = typ[:len(typ)-1]

				refName, err := bufReader.ReadString('\n')
				if err == io.EOF {
					// This should not happen, but we'll tolerate it
					break
				}
				if err != nil {
					return err
				}
				refName = refName[:len(refName)-1]

				// refName cannot be HEAD but can be remotes or stash
				if strings.HasPrefix(refName, RemotePrefix) || refName == "/refs/stash" {
					continue
				}

				if pattern == "" || strings.HasPrefix(refName, pattern) {
					r := &Reference{
						Name:   refName,
						Object: MustIDFromString(sha),
						Type:   typ,
						repo:   repo,
					}
					refs = append(refs, r)
				}
			}
			return nil
		}).RunWithStderr(ctx)
	return refs, err
}