package edit

import (
	"fmt"
	"net/http"
	"slices"
	"strings"
	"time"

	"github.com/MakeNowJust/heredoc"
	"github.com/cli/cli/v2/api"
	fd "github.com/cli/cli/v2/internal/featuredetection"
	"github.com/cli/cli/v2/internal/gh"
	"github.com/cli/cli/v2/internal/ghrepo"
	"github.com/cli/cli/v2/internal/prompter"
	shared "github.com/cli/cli/v2/pkg/cmd/pr/shared"
	"github.com/cli/cli/v2/pkg/cmdutil"
	"github.com/cli/cli/v2/pkg/iostreams"
	"github.com/cli/cli/v2/pkg/set"
	"github.com/spf13/cobra"
	"golang.org/x/sync/errgroup"
)

type EditOptions struct {
	HttpClient func() (*http.Client, error)
	IO         *iostreams.IOStreams

	Finder          shared.PRFinder
	Surveyor        Surveyor
	Fetcher         EditableOptionsFetcher
	EditorRetriever EditorRetriever
	Prompter        shared.EditPrompter
	Detector        fd.Detector
	BaseRepo        func() (ghrepo.Interface, error)

	SelectorArg string
	Interactive bool

	shared.Editable
}

func NewCmdEdit(f *cmdutil.Factory, runF func(*EditOptions) error) *cobra.Command {
	opts := &EditOptions{
		IO:              f.IOStreams,
		HttpClient:      f.HttpClient,
		Surveyor:        surveyor{P: f.Prompter},
		Fetcher:         fetcher{},
		EditorRetriever: editorRetriever{config: f.Config},
		Prompter:        f.Prompter,
	}

	var bodyFile string
	var removeMilestone bool

	cmd := &cobra.Command{
		Use:   "edit [<number> | <url> | <branch>]",
		Short: "Edit a pull request",
		Long: heredoc.Docf(`
			Edit a pull request.

			Without an argument, the pull request that belongs to the current branch
			is selected.

			Editing a pull request's projects requires authorization with the %[1]sproject%[1]s scope.
			To authorize, run %[1]sgh auth refresh -s project%[1]s.

			The %[1]s--add-assignee%[1]s and %[1]s--remove-assignee%[1]s flags both support
			the following special values:
			- %[1]s@me%[1]s: assign or unassign yourself
			- %[1]s@copilot%[1]s: assign or unassign Copilot (not supported on GitHub Enterprise Server)

			The %[1]s--add-reviewer%[1]s and %[1]s--remove-reviewer%[1]s flags support
			the following special value:
			- %[1]s@copilot%[1]s: request or remove review from Copilot (not supported on GitHub Enterprise Server)
		`, "`"),
		Example: heredoc.Doc(`
			# Edit the title and body of a pull request
			$ gh pr edit 23 --title "I found a bug" --body "Nothing works"

			# Use a file as the body
			$ gh pr edit 23 --body-file body.txt

			# Manage labels
			$ gh pr edit 23 --add-label "bug,help wanted" --remove-label "core"

			# Manage reviewers
			$ gh pr edit 23 --add-reviewer monalisa,hubot --remove-reviewer myorg/team-name

			# Re-request review
			$ gh pr edit 23 --add-reviewer monalisa

			# Request a review from GitHub Copilot
			$ gh pr edit 23 --add-reviewer "@copilot"

			# Manage assignees
			$ gh pr edit 23 --add-assignee "@me" --remove-assignee monalisa,hubot

			# Assign GitHub Copilot
			$ gh pr edit 23 --add-assignee "@copilot"

			# Manage projects and milestones
			$ gh pr edit 23 --add-project "Roadmap" --remove-project v1,v2
			$ gh pr edit 23 --milestone "Version 1"
			$ gh pr edit 23 --remove-milestone
		`),
		Args: cobra.MaximumNArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			opts.Finder = shared.NewFinder(f)

			// support `-R, --repo` override
			opts.BaseRepo = f.BaseRepo

			if len(args) > 0 {
				opts.SelectorArg = args[0]
			}

			if opts.SelectorArg != "" {
				// If a URL is provided, we need to parse it to override the
				// base repository, especially the hostname part. That's because
				// we need a feature detector down in this command, and that
				// needs to know the API host. If the command is run outside of
				// a git repo, we cannot instantiate the detector unless we have
				// already parsed the URL.
				if baseRepo, _, _, err := shared.ParseURL(opts.SelectorArg); err == nil {
					opts.BaseRepo = func() (ghrepo.Interface, error) {
						return baseRepo, nil
					}
				}
			}

			flags := cmd.Flags()

			bodyProvided := flags.Changed("body")
			bodyFileProvided := bodyFile != ""

			if err := cmdutil.MutuallyExclusive(
				"specify only one of `--body` or `--body-file`",
				bodyProvided,
				bodyFileProvided,
			); err != nil {
				return err
			}
			if bodyProvided || bodyFileProvided {
				opts.Editable.Body.Edited = true
				if bodyFileProvided {
					b, err := cmdutil.ReadFile(bodyFile, opts.IO.In)
					if err != nil {
						return err
					}
					opts.Editable.Body.Value = string(b)
				}
			}

			if err := cmdutil.MutuallyExclusive(
				"specify only one of `--milestone` or `--remove-milestone`",
				flags.Changed("milestone"),
				removeMilestone,
			); err != nil {
				return err
			}

			if flags.Changed("title") {
				opts.Editable.Title.Edited = true
			}
			if flags.Changed("body") {
				opts.Editable.Body.Edited = true
			}
			if flags.Changed("base") {
				opts.Editable.Base.Edited = true
			}
			if flags.Changed("add-reviewer") || flags.Changed("remove-reviewer") {
				opts.Editable.Reviewers.Edited = true
			}
			if flags.Changed("add-assignee") || flags.Changed("remove-assignee") {
				opts.Editable.Assignees.Edited = true
			}
			if flags.Changed("add-label") || flags.Changed("remove-label") {
				opts.Editable.Labels.Edited = true
			}
			if flags.Changed("add-project") || flags.Changed("remove-project") {
				opts.Editable.Projects.Edited = true
			}
			if flags.Changed("milestone") || removeMilestone {
				opts.Editable.Milestone.Edited = true

				// Note that when `--remove-milestone` is provided, the value of
				// `opts.Editable.Milestone.Value` will automatically be empty,
				// which results in milestone association removal. For reference,
				// see the `Editable.MilestoneId` method.
			}

			if !opts.Editable.Dirty() {
				opts.Interactive = true
			}

			if opts.Interactive && !opts.IO.CanPrompt() {
				return cmdutil.FlagErrorf("--title, --body, --reviewer, --assignee, --label, --project, or --milestone required when not running interactively")
			}

			if runF != nil {
				return runF(opts)
			}

			return editRun(opts)
		},
	}

	cmd.Flags().StringVarP(&opts.Editable.Title.Value, "title", "t", "", "Set the new title.")
	cmd.Flags().StringVarP(&opts.Editable.Body.Value, "body", "b", "", "Set the new body.")
	cmd.Flags().StringVarP(&bodyFile, "body-file", "F", "", "Read body text from `file` (use \"-\" to read from standard input)")
	cmd.Flags().StringVarP(&opts.Editable.Base.Value, "base", "B", "", "Change the base `branch` for this pull request")
	cmd.Flags().StringSliceVar(&opts.Editable.Reviewers.Add, "add-reviewer", nil, "Add or re-request reviewers by their `login`. Use \"@copilot\" to request review from Copilot.")
	cmd.Flags().StringSliceVar(&opts.Editable.Reviewers.Remove, "remove-reviewer", nil, "Remove reviewers by their `login`. Use \"@copilot\" to remove review request from Copilot.")
	cmd.Flags().StringSliceVar(&opts.Editable.Assignees.Add, "add-assignee", nil, "Add assigned users by their `login`. Use \"@me\" to assign yourself, or \"@copilot\" to assign Copilot.")
	cmd.Flags().StringSliceVar(&opts.Editable.Assignees.Remove, "remove-assignee", nil, "Remove assigned users by their `login`. Use \"@me\" to unassign yourself, or \"@copilot\" to unassign Copilot.")
	cmd.Flags().StringSliceVar(&opts.Editable.Labels.Add, "add-label", nil, "Add labels by `name`")
	cmd.Flags().StringSliceVar(&opts.Editable.Labels.Remove, "remove-label", nil, "Remove labels by `name`")
	cmd.Flags().StringSliceVar(&opts.Editable.Projects.Add, "add-project", nil, "Add the pull request to projects by `title`")
	cmd.Flags().StringSliceVar(&opts.Editable.Projects.Remove, "remove-project", nil, "Remove the pull request from projects by `title`")
	cmd.Flags().StringVarP(&opts.Editable.Milestone.Value, "milestone", "m", "", "Edit the milestone the pull request belongs to by `name`")
	cmd.Flags().BoolVar(&removeMilestone, "remove-milestone", false, "Remove the milestone association from the pull request")

	_ = cmdutil.RegisterBranchCompletionFlags(f.GitClient, cmd, "base")

	for _, flagName := range []string{"add-reviewer", "remove-reviewer"} {
		_ = cmd.RegisterFlagCompletionFunc(flagName, func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
			baseRepo, err := f.BaseRepo()
			if err != nil {
				return nil, cobra.ShellCompDirectiveError
			}
			httpClient, err := f.HttpClient()
			if err != nil {
				return nil, cobra.ShellCompDirectiveError
			}
			results, err := shared.RequestableReviewersForCompletion(httpClient, baseRepo)
			if err != nil {
				return nil, cobra.ShellCompDirectiveError
			}
			return results, cobra.ShellCompDirectiveNoFileComp
		})
	}

	return cmd
}

func editRun(opts *EditOptions) error {
	httpClient, err := opts.HttpClient()
	if err != nil {
		return err
	}

	if opts.Detector == nil {
		baseRepo, err := opts.BaseRepo()
		if err != nil {
			return err
		}

		cachedClient := api.NewCachedHTTPClient(httpClient, time.Hour*24)
		opts.Detector = fd.NewDetector(cachedClient, baseRepo.RepoHost())
	}

	findOptions := shared.FindOptions{
		Selector: opts.SelectorArg,
		Fields:   []string{"id", "author", "url", "title", "body", "baseRefName", "reviewRequests", "labels", "projectCards", "projectItems", "milestone"},
		Detector: opts.Detector,
	}

	issueFeatures, err := opts.Detector.IssueFeatures()
	if err != nil {
		return err
	}

	// TODO ApiActorsSupported
	if issueFeatures.ApiActorsSupported {
		findOptions.Fields = append(findOptions.Fields, "assignedActors")
	} else {
		findOptions.Fields = append(findOptions.Fields, "assignees")
	}

	pr, repo, err := opts.Finder.Find(findOptions)
	if err != nil {
		return err
	}

	editable := opts.Editable
	editable.Reviewers.Allowed = true
	editable.Title.Default = pr.Title
	editable.Body.Default = pr.Body
	editable.Base.Default = pr.BaseRefName
	editable.Reviewers.Default = pr.ReviewRequests.DisplayNames()
	editable.Reviewers.DefaultLogins = pr.ReviewRequests.Logins()
	// TODO ApiActorsSupported
	if issueFeatures.ApiActorsSupported {
		editable.ApiActorsSupported = true
		editable.Assignees.Default = pr.AssignedActors.DisplayNames()
		editable.Assignees.DefaultLogins = pr.AssignedActors.Logins()
	} else {
		editable.Assignees.Default = pr.Assignees.Logins()
	}
	editable.Labels.Default = pr.Labels.Names()
	editable.Projects.Default = append(pr.ProjectCards.ProjectNames(), pr.ProjectItems.ProjectTitles()...)
	projectItems := map[string]string{}
	for _, n := range pr.ProjectItems.Nodes {
		projectItems[n.Project.ID] = n.ID
	}
	editable.Projects.ProjectItems = projectItems
	if pr.Milestone != nil {
		editable.Milestone.Default = pr.Milestone.Title
	}

	if opts.Interactive {
		err = opts.Surveyor.FieldsToEdit(&editable)
		if err != nil {
			return err
		}
	}

	apiClient := api.NewClientFromHTTP(httpClient)

	// Wire up search functions for assignees and reviewers.
	// When these aren't wired up, it triggers a downstream fallback
	// to legacy reviewer/assignee fetching.
	// TODO ApiActorsSupported
	if issueFeatures.ApiActorsSupported {
		editable.AssigneeSearchFunc = shared.AssigneeSearchFunc(apiClient, repo, pr.ID)
		editable.ReviewerSearchFunc = reviewerSearchFunc(apiClient, repo, &editable, pr.ID)
	}

	opts.IO.StartProgressIndicator()
	err = opts.Fetcher.EditableOptionsFetch(apiClient, repo, &editable, opts.Detector.ProjectsV1())
	opts.IO.StopProgressIndicator()
	if err != nil {
		return err
	}

	if opts.Interactive {
		// Remove PR author from reviewer options;
		// REST API errors if author is included (GraphQL silently ignores).
		if editable.Reviewers.Edited {
			s := set.NewStringSet()
			s.AddValues(editable.Reviewers.Options)
			s.Remove(pr.Author.Login)
			editable.Reviewers.Options = s.ToSlice()
		}

		editorCommand, err := opts.EditorRetriever.Retrieve()
		if err != nil {
			return err
		}
		err = opts.Surveyor.EditFields(&editable, editorCommand)
		if err != nil {
			return err
		}
	}

	opts.IO.StartProgressIndicator()
	err = updatePullRequest(httpClient, repo, pr.ID, pr.Number, editable)
	opts.IO.StopProgressIndicator()
	if err != nil {
		return err
	}

	fmt.Fprintln(opts.IO.Out, pr.URL)

	return nil
}

// reviewerSearchFunc is intended to be an arg for MultiSelectWithSearch
// to return potential reviewer candidates (users, bots, and teams).
// It also updates the editable's metadata for later ID resolution.
func reviewerSearchFunc(apiClient *api.Client, repo ghrepo.Interface, editable *shared.Editable, prID string) func(string) prompter.MultiSelectSearchResult {
	searchFunc := func(input string) prompter.MultiSelectSearchResult {
		candidates, moreResults, err := api.SuggestedReviewerActors(
			apiClient,
			repo,
			prID,
			input)
		if err != nil {
			return prompter.MultiSelectSearchResult{
				Keys:        nil,
				Labels:      nil,
				MoreResults: 0,
				Err:         err,
			}
		}

		keys := make([]string, 0, len(candidates))
		labels := make([]string, 0, len(candidates))

		for _, c := range candidates {
			keys = append(keys, c.Login())
			labels = append(labels, c.DisplayName())

			// Update the teams metadata in the editable struct
			// so that updating the PR later can resolve the team ID.
			if team, ok := c.(api.ReviewerTeam); ok {
				editable.Metadata.Teams = append(editable.Metadata.Teams, api.OrgTeam{
					ID:   "", // ID not needed for REST API reviewer mutations
					Slug: team.Slug(),
				})
			}
		}
		return prompter.MultiSelectSearchResult{
			Keys:        keys,
			Labels:      labels,
			MoreResults: moreResults,
			Err:         nil,
		}
	}
	return searchFunc
}

func updatePullRequest(httpClient *http.Client, repo ghrepo.Interface, id string, number int, editable shared.Editable) error {
	var wg errgroup.Group
	wg.Go(func() error {
		return shared.UpdateIssue(httpClient, repo, id, true, editable)
	})
	if editable.Reviewers.Edited {
		wg.Go(func() error {
			return updatePullRequestReviews(httpClient, repo, id, number, editable)
		})
	}
	return wg.Wait()
}

func updatePullRequestReviews(httpClient *http.Client, repo ghrepo.Interface, prID string, number int, editable shared.Editable) error {
	if !editable.Reviewers.Edited {
		return nil
	}

	client := api.NewClientFromHTTP(httpClient)

	// Rebuild the Value slice from non-interactive flag input.
	if len(editable.Reviewers.Add) != 0 || len(editable.Reviewers.Remove) != 0 {
		add := editable.Reviewers.Add
		remove := editable.Reviewers.Remove

		// Replace @copilot with the Copilot reviewer login (only on github.com).
		// Also use DefaultLogins (not Default display names) for computing the set.
		var defaultLogins []string
		// TODO ApiActorsSupported
		if editable.ApiActorsSupported {
			copilotReplacer := shared.NewCopilotReviewerReplacer()
			add = copilotReplacer.ReplaceSlice(add)
			remove = copilotReplacer.ReplaceSlice(remove)
			defaultLogins = editable.Reviewers.DefaultLogins
		} else {
			// On GHES, Default already contains logins (no display name distinction)
			defaultLogins = editable.Reviewers.Default
		}

		s := set.NewStringSet()
		s.AddValues(add)
		s.AddValues(defaultLogins)
		s.RemoveValues(remove)
		editable.Reviewers.Value = s.ToSlice()
	}

	// On github.com, use the new GraphQL mutation which supports bots.
	// On GHES, fall back to REST API.
	// TODO ApiActorsSupported
	if editable.ApiActorsSupported {
		return updatePullRequestReviewsGraphQL(client, repo, prID, editable)
	}
	return updatePullRequestReviewsREST(client, repo, number, editable)
}

// updatePullRequestReviewsGraphQL uses the RequestReviewsByLogin mutation.
// This mutation replaces the entire reviewer set (union: false).
func updatePullRequestReviewsGraphQL(client *api.Client, repo ghrepo.Interface, prID string, editable shared.Editable) error {
	users, bots, teams := partitionReviewersByType(editable.Reviewers.Value)
	return api.RequestReviewsByLogin(client, repo, prID, users, bots, teams, false)
}

// updatePullRequestReviewsREST uses the REST API to add/remove reviewers.
// This is the legacy path for GHES compatibility.
func updatePullRequestReviewsREST(client *api.Client, repo ghrepo.Interface, number int, editable shared.Editable) error {
	addUsers, addBots, addTeams := partitionReviewersByType(editable.Reviewers.Value)
	// REST API doesn't distinguish bots from users, so we need to combine them.
	allAddUsers := append(addUsers, addBots...)

	// Reviewers in Default but not in Value have been removed interactively.
	var toRemove []string
	for _, r := range editable.Reviewers.Default {
		if !slices.Contains(editable.Reviewers.Value, r) {
			toRemove = append(toRemove, r)
		}
	}
	removeUsers, removeBots, removeTeams := partitionReviewersByType(toRemove)
	allRemoveUsers := append(removeUsers, removeBots...)

	wg := errgroup.Group{}
	wg.Go(func() error {
		return api.AddPullRequestReviews(client, repo, number, allAddUsers, addTeams)
	})
	wg.Go(func() error {
		return api.RemovePullRequestReviews(client, repo, number, allRemoveUsers, removeTeams)
	})
	return wg.Wait()
}

type Surveyor interface {
	FieldsToEdit(*shared.Editable) error
	EditFields(*shared.Editable, string) error
}

type surveyor struct {
	P shared.EditPrompter
}

func (s surveyor) FieldsToEdit(editable *shared.Editable) error {
	return shared.FieldsToEditSurvey(s.P, editable)
}

func (s surveyor) EditFields(editable *shared.Editable, editorCmd string) error {
	return shared.EditFieldsSurvey(s.P, editable, editorCmd)
}

type EditableOptionsFetcher interface {
	EditableOptionsFetch(*api.Client, ghrepo.Interface, *shared.Editable, gh.ProjectsV1Support) error
}

type fetcher struct{}

func (f fetcher) EditableOptionsFetch(client *api.Client, repo ghrepo.Interface, opts *shared.Editable, projectsV1Support gh.ProjectsV1Support) error {
	return shared.FetchOptions(client, repo, opts, projectsV1Support)
}

type EditorRetriever interface {
	Retrieve() (string, error)
}

type editorRetriever struct {
	config func() (gh.Config, error)
}

func (e editorRetriever) Retrieve() (string, error) {
	return cmdutil.DetermineEditor(e.config)
}

// partitionReviewersByType splits reviewer identifiers into users, bots, and teams.
// Team identifiers are in the form "org/slug" and are returned as-is.
// Bot logins (currently only Copilot) are identified and returned separately.
func partitionReviewersByType(values []string) (users []string, bots []string, teams []string) {
	for _, v := range values {
		if v == "" {
			continue
		}
		if strings.ContainsRune(v, '/') {
			// Team: org/slug format, pass as-is
			teams = append(teams, v)
		} else if v == api.CopilotReviewerLogin {
			bots = append(bots, v)
		} else {
			users = append(users, v)
		}
	}
	return
}
