// Copyright 2026 The Gitea Authors. All rights reserved.
// SPDX-License-Identifier: MIT

package app

import (
	"cmp"
	"errors"
	"fmt"
	"strings"

	"gitea.dev/tea/internal/clierr"
	"gitea.dev/tea/internal/git"
	"gitea.dev/tea/internal/services"
	"gitea.dev/tea/internal/settings"
	"github.com/spf13/cobra"
)

func (a *application) repositorySyncCommand() *cobra.Command {
	var branch string
	command := &cobra.Command{
		Use:   "sync [<repository>]",
		Short: "Sync a branch with its remote or its fork's parent",
		Long: `Fast-forward a local branch to the branch of the same name on the repository's Git remote.

The branch defaults to the repository's default branch. It is created when it is missing, and it is
never checked out: the branch you are on stays checked out. When the branch is checked out, the
working tree must be clean. Branches that have diverged from the remote are left unchanged.

Given a repository that has no remote in the current directory, sync updates it on the server
instead: a fork's branch is fast-forwarded to its parent's, and a pull mirror fetches its source.`,
		Example: `# Fast-forward the default branch from the repository's remote
$ tea repo sync

# Fast-forward another branch
$ tea repo sync --branch release/1.0

# Update a fork on the server from its parent
$ tea repo sync bob/project`,
		Annotations: map[string]string{"tea.arguments": repositoryArguments},
		Args:        usageArgs(cobra.MaximumNArgs(1)),
		RunE: func(cmd *cobra.Command, args []string) error {
			if cmd.Flags().Changed("branch") && strings.TrimSpace(branch) == "" {
				return clierr.Wrap(clierr.Usage, errors.New("--branch cannot be empty"))
			}
			if err := a.repositoryArgument(args); err != nil {
				return err
			}
			target, err := a.resolve(cmd.Context(), true)
			if err != nil {
				return err
			}
			snapshot, err := a.deps.Settings.Load()
			if err != nil {
				return err
			}
			inside, _ := a.gitProbe().Output(cmd.Context(), a.options.cwd, false, "rev-parse", "--is-inside-work-tree")
			remote, err := "", errNoMatchingRemote
			if inside == "true" {
				remote, err = a.checkoutRemote(cmd.Context(), target, snapshot)
			}
			switch {
			case errors.Is(err, errNoMatchingRemote) && len(args) > 0:
				return a.syncOnServer(cmd, target, branch)
			case inside != "true":
				return clierr.Wrap(clierr.Usage, fmt.Errorf("repo sync needs a Git clone of %s; run it inside one, or pass a fork to update it on the server: tea repo sync OWNER/REPO", target.Repo))
			case errors.Is(err, errNoMatchingRemote):
				return clierr.Wrap(clierr.Usage, errors.New("no Git remote of this clone points to "+target.Repo+"; add one with git remote add, or pass --remote"))
			case err != nil:
				return clierr.Wrap(clierr.Usage, err)
			}
			if branch == "" {
				repository, err := (services.Repositories{Client: target.client}).View(cmd.Context(), target.Repo)
				if err != nil {
					return err
				}
				branch = repository.DefaultBranch
			}
			raw, err := a.git(cmd.Context(), "remote", "get-url", remote)
			if err != nil {
				return err
			}
			if !target.ownsRemote(raw) {
				return clierr.Wrap(clierr.Usage, errors.New("selected Git remote changed; resolve the repository again before sync"))
			}
			credentials, err := a.gitTransportArguments(target, settings.RemoteIsSSH(raw))
			if err != nil {
				return err
			}
			result, err := git.SyncBranch(cmd.Context(), a.deps.Git, git.SyncOptions{Directory: a.options.cwd, Remote: remote, Branch: branch, CredentialArgs: credentials, Prompt: a.policy(snapshot).CanPrompt(a.deps.Streams)})
			if err != nil {
				return err
			}
			a.reportSync(cmd, result, remote+"/"+result.Branch)
			return a.jsonResult(cmd, result)
		},
	}
	command.Flags().StringVarP(&branch, "branch", "b", "", "Branch to sync (default: the repository's default branch)")
	_ = command.RegisterFlagCompletionFunc("branch", a.completeBranches())
	command.ValidArgsFunction = a.completeRepos()
	return command
}

// syncOnServer updates the repository of t on the server: a fork's branch, the default branch
// unless named, fast-forwards to its parent's, and a pull mirror fetches its source.
func (a *application) syncOnServer(cmd *cobra.Command, t target, branch string) error {
	repositories := services.Repositories{Client: t.client}
	item, err := repositories.View(cmd.Context(), t.Repo)
	if err != nil {
		return err
	}
	switch {
	case item.Mirror:
		if err := repositories.MirrorSync(cmd.Context(), item.FullName); err != nil {
			return err
		}
		a.done(cmd, "Started updating the mirror %s from its source", item.FullName)
		return a.jsonResult(cmd, git.SyncResult{Remote: mirrorSourceURL(item)})
	case !item.Fork || item.Parent == nil:
		return clierr.Wrap(clierr.Usage, fmt.Errorf("%s is neither a fork nor a mirror, and has no Git remote here; run tea repo sync inside a clone of it", item.FullName))
	}
	branch = cmp.Or(branch, item.DefaultBranch)
	branches := services.Branches{Client: t.client}
	before, err := branches.View(cmd.Context(), item.FullName, branch)
	if err != nil {
		return err
	}
	if _, err := repositories.MergeUpstream(cmd.Context(), item.FullName, branch); err != nil {
		return err
	}
	after, err := branches.View(cmd.Context(), item.FullName, branch)
	if err != nil {
		return err
	}
	result := git.SyncResult{Branch: branch, Commit: after.SHA, Previous: before.SHA, Remote: item.Parent.FullName}
	if result.Previous == result.Commit {
		a.done(cmd, "%s %s is already up to date with %s", item.FullName, branch, item.Parent.FullName)
	} else {
		a.done(cmd, "Synced %s %s from %s (fast-forward %s..%s)", item.FullName, branch, item.Parent.FullName, shortSHA(result.Previous), shortSHA(result.Commit))
	}
	return a.jsonResult(cmd, result)
}

// reportSync tells how a sync from source, such as origin/main, changed the branch.
func (a *application) reportSync(cmd *cobra.Command, result git.SyncResult, source string) {
	switch result.Previous {
	case result.Commit:
		a.done(cmd, "%s is already up to date with %s", result.Branch, source)
	case "":
		a.done(cmd, "Created %s from %s (%s)", result.Branch, source, shortSHA(result.Commit))
	default:
		a.done(cmd, "Synced %s from %s (fast-forward %s..%s)", result.Branch, source, shortSHA(result.Previous), shortSHA(result.Commit))
	}
}