package command

import (
	"errors"
	"fmt"
	"io"
	"net/url"
	"regexp"
	"strconv"
	"strings"
	"time"

	"github.com/MakeNowJust/heredoc"
	"github.com/cli/cli/api"
	"github.com/cli/cli/git"
	"github.com/cli/cli/internal/ghrepo"
	"github.com/cli/cli/pkg/githubtemplate"
	"github.com/cli/cli/utils"
	"github.com/spf13/cobra"
	"github.com/spf13/pflag"
)

func init() {
	RootCmd.AddCommand(issueCmd)
	issueCmd.AddCommand(issueStatusCmd)

	issueCmd.AddCommand(issueCreateCmd)
	issueCreateCmd.Flags().StringP("title", "t", "",
		"Supply a title. Will prompt for one otherwise.")
	issueCreateCmd.Flags().StringP("body", "b", "",
		"Supply a body. Will prompt for one otherwise.")
	issueCreateCmd.Flags().BoolP("web", "w", false, "Open the browser to create an issue")
	issueCreateCmd.Flags().StringSliceP("assignee", "a", nil, "Assign a person by their `login`")
	issueCreateCmd.Flags().StringSliceP("label", "l", nil, "Add a label by `name`")
	issueCreateCmd.Flags().StringSliceP("project", "p", nil, "Add the issue to a project by `name`")
	issueCreateCmd.Flags().StringP("milestone", "m", "", "Add the issue to a milestone by `name`")

	issueCmd.AddCommand(issueListCmd)
	issueListCmd.Flags().StringP("assignee", "a", "", "Filter by assignee")
	issueListCmd.Flags().StringSliceP("label", "l", nil, "Filter by label")
	issueListCmd.Flags().StringP("state", "s", "open", "Filter by state: {open|closed|all}")
	issueListCmd.Flags().IntP("limit", "L", 30, "Maximum number of issues to fetch")
	issueListCmd.Flags().StringP("author", "A", "", "Filter by author")
	issueListCmd.Flags().StringP("mention", "", "", "Filter by mention")
	issueListCmd.Flags().StringP("milestone", "", "", "Filter by milestone")

	issueCmd.AddCommand(issueViewCmd)
	issueViewCmd.Flags().BoolP("web", "w", false, "Open an issue in the browser")

	issueCmd.AddCommand(issueCloseCmd)
	issueCmd.AddCommand(issueReopenCmd)
}

var issueCmd = &cobra.Command{
	Use:   "issue <command>",
	Short: "Create and view issues",
	Long:  `Work with GitHub issues`,
	Example: heredoc.Doc(`
	$ gh issue list
	$ gh issue create --label bug
	$ gh issue view --web
	`),
	Annotations: map[string]string{
		"IsCore": "true",
		"help:arguments": `An issue can be supplied as argument in any of the following formats:
- by number, e.g. "123"; or
- by URL, e.g. "https://github.com/OWNER/REPO/issues/123".`},
}
var issueCreateCmd = &cobra.Command{
	Use:   "create",
	Short: "Create a new issue",
	RunE:  issueCreate,
}
var issueListCmd = &cobra.Command{
	Use:   "list",
	Short: "List and filter issues in this repository",
	RunE:  issueList,
}
var issueStatusCmd = &cobra.Command{
	Use:   "status",
	Short: "Show status of relevant issues",
	RunE:  issueStatus,
}
var issueViewCmd = &cobra.Command{
	Use:   "view {<number> | <url>}",
	Short: "View an issue",
	Args:  cobra.ExactArgs(1),
	Long: `Display the title, body, and other information about an issue.

With '--web', open the issue in a web browser instead.`,
	RunE: issueView,
}
var issueCloseCmd = &cobra.Command{
	Use:   "close {<number> | <url>}",
	Short: "Close issue",
	Args:  cobra.ExactArgs(1),
	RunE:  issueClose,
}
var issueReopenCmd = &cobra.Command{
	Use:   "reopen {<number> | <url>}",
	Short: "Reopen issue",
	Args:  cobra.ExactArgs(1),
	RunE:  issueReopen,
}

func issueList(cmd *cobra.Command, args []string) error {
	ctx := contextForCommand(cmd)
	apiClient, err := apiClientForContext(ctx)
	if err != nil {
		return err
	}

	baseRepo, err := determineBaseRepo(apiClient, cmd, ctx)
	if err != nil {
		return err
	}

	state, err := cmd.Flags().GetString("state")
	if err != nil {
		return err
	}

	labels, err := cmd.Flags().GetStringSlice("label")
	if err != nil {
		return err
	}

	assignee, err := cmd.Flags().GetString("assignee")
	if err != nil {
		return err
	}

	limit, err := cmd.Flags().GetInt("limit")
	if err != nil {
		return err
	}
	if limit <= 0 {
		return fmt.Errorf("invalid limit: %v", limit)
	}

	author, err := cmd.Flags().GetString("author")
	if err != nil {
		return err
	}

	mention, err := cmd.Flags().GetString("mention")
	if err != nil {
		return err
	}

	milestone, err := cmd.Flags().GetString("milestone")
	if err != nil {
		return err
	}

	listResult, err := api.IssueList(apiClient, baseRepo, state, labels, assignee, limit, author, mention, milestone)
	if err != nil {
		return err
	}

	hasFilters := false
	cmd.Flags().Visit(func(f *pflag.Flag) {
		switch f.Name {
		case "state", "label", "assignee", "author":
			hasFilters = true
		}
	})

	title := listHeader(ghrepo.FullName(baseRepo), "issue", len(listResult.Issues), listResult.TotalCount, hasFilters)
	// TODO: avoid printing header if piped to a script
	fmt.Fprintf(colorableErr(cmd), "\n%s\n\n", title)

	out := cmd.OutOrStdout()

	printIssues(out, "", len(listResult.Issues), listResult.Issues)

	return nil
}

func issueStatus(cmd *cobra.Command, args []string) error {
	ctx := contextForCommand(cmd)
	apiClient, err := apiClientForContext(ctx)
	if err != nil {
		return err
	}

	baseRepo, err := determineBaseRepo(apiClient, cmd, ctx)
	if err != nil {
		return err
	}

	currentUser, err := api.CurrentLoginName(apiClient)
	if err != nil {
		return err
	}

	issuePayload, err := api.IssueStatus(apiClient, baseRepo, currentUser)
	if err != nil {
		return err
	}

	out := colorableOut(cmd)

	fmt.Fprintln(out, "")
	fmt.Fprintf(out, "Relevant issues in %s\n", ghrepo.FullName(baseRepo))
	fmt.Fprintln(out, "")

	printHeader(out, "Issues assigned to you")
	if issuePayload.Assigned.TotalCount > 0 {
		printIssues(out, "  ", issuePayload.Assigned.TotalCount, issuePayload.Assigned.Issues)
	} else {
		message := "  There are no issues assigned to you"
		printMessage(out, message)
	}
	fmt.Fprintln(out)

	printHeader(out, "Issues mentioning you")
	if issuePayload.Mentioned.TotalCount > 0 {
		printIssues(out, "  ", issuePayload.Mentioned.TotalCount, issuePayload.Mentioned.Issues)
	} else {
		printMessage(out, "  There are no issues mentioning you")
	}
	fmt.Fprintln(out)

	printHeader(out, "Issues opened by you")
	if issuePayload.Authored.TotalCount > 0 {
		printIssues(out, "  ", issuePayload.Authored.TotalCount, issuePayload.Authored.Issues)
	} else {
		printMessage(out, "  There are no issues opened by you")
	}
	fmt.Fprintln(out)

	return nil
}

func issueView(cmd *cobra.Command, args []string) error {
	ctx := contextForCommand(cmd)

	apiClient, err := apiClientForContext(ctx)
	if err != nil {
		return err
	}

	baseRepo, err := determineBaseRepo(apiClient, cmd, ctx)
	if err != nil {
		return err
	}

	issue, err := issueFromArg(apiClient, baseRepo, args[0])
	if err != nil {
		return err
	}
	openURL := issue.URL

	web, err := cmd.Flags().GetBool("web")
	if err != nil {
		return err
	}

	if web {
		fmt.Fprintf(cmd.ErrOrStderr(), "Opening %s in your browser.\n", openURL)
		return utils.OpenInBrowser(openURL)
	}
	out := colorableOut(cmd)
	return printIssuePreview(out, issue)
}

func issueStateTitleWithColor(state string) string {
	colorFunc := colorFuncForState(state)
	return colorFunc(strings.Title(strings.ToLower(state)))
}

func listHeader(repoName string, itemName string, matchCount int, totalMatchCount int, hasFilters bool) string {
	if totalMatchCount == 0 {
		if hasFilters {
			return fmt.Sprintf("No %ss match your search in %s", itemName, repoName)
		}
		return fmt.Sprintf("There are no open %ss in %s", itemName, repoName)
	}

	if hasFilters {
		matchVerb := "match"
		if totalMatchCount == 1 {
			matchVerb = "matches"
		}
		return fmt.Sprintf("Showing %d of %s in %s that %s your search", matchCount, utils.Pluralize(totalMatchCount, itemName), repoName, matchVerb)
	}

	return fmt.Sprintf("Showing %d of %s in %s", matchCount, utils.Pluralize(totalMatchCount, itemName), repoName)
}

func printIssuePreview(out io.Writer, issue *api.Issue) error {
	now := time.Now()
	ago := now.Sub(issue.CreatedAt)

	// Header (Title and State)
	fmt.Fprintln(out, utils.Bold(issue.Title))
	fmt.Fprint(out, issueStateTitleWithColor(issue.State))
	fmt.Fprintln(out, utils.Gray(fmt.Sprintf(
		" • %s opened %s • %s",
		issue.Author.Login,
		utils.FuzzyAgo(ago),
		utils.Pluralize(issue.Comments.TotalCount, "comment"),
	)))

	// Metadata
	fmt.Fprintln(out)
	if assignees := issueAssigneeList(*issue); assignees != "" {
		fmt.Fprint(out, utils.Bold("Assignees: "))
		fmt.Fprintln(out, assignees)
	}
	if labels := issueLabelList(*issue); labels != "" {
		fmt.Fprint(out, utils.Bold("Labels: "))
		fmt.Fprintln(out, labels)
	}
	if projects := issueProjectList(*issue); projects != "" {
		fmt.Fprint(out, utils.Bold("Projects: "))
		fmt.Fprintln(out, projects)
	}
	if issue.Milestone.Title != "" {
		fmt.Fprint(out, utils.Bold("Milestone: "))
		fmt.Fprintln(out, issue.Milestone.Title)
	}

	// Body
	if issue.Body != "" {
		fmt.Fprintln(out)
		md, err := utils.RenderMarkdown(issue.Body)
		if err != nil {
			return err
		}
		fmt.Fprintln(out, md)
	}
	fmt.Fprintln(out)

	// Footer
	fmt.Fprintf(out, utils.Gray("View this issue on GitHub: %s\n"), issue.URL)
	return nil
}

var issueURLRE = regexp.MustCompile(`^https://github\.com/([^/]+)/([^/]+)/issues/(\d+)`)

func issueFromArg(apiClient *api.Client, baseRepo ghrepo.Interface, arg string) (*api.Issue, error) {
	if issueNumber, err := strconv.Atoi(strings.TrimPrefix(arg, "#")); err == nil {
		return api.IssueByNumber(apiClient, baseRepo, issueNumber)
	}

	if m := issueURLRE.FindStringSubmatch(arg); m != nil {
		issueNumber, _ := strconv.Atoi(m[3])
		return api.IssueByNumber(apiClient, baseRepo, issueNumber)
	}

	return nil, fmt.Errorf("invalid issue format: %q", arg)
}

func issueCreate(cmd *cobra.Command, args []string) error {
	ctx := contextForCommand(cmd)
	apiClient, err := apiClientForContext(ctx)
	if err != nil {
		return err
	}

	// NB no auto forking like over in pr create
	baseRepo, err := determineBaseRepo(apiClient, cmd, ctx)
	if err != nil {
		return err
	}

	baseOverride, err := cmd.Flags().GetString("repo")
	if err != nil {
		return err
	}

	var nonLegacyTemplateFiles []string
	if baseOverride == "" {
		if rootDir, err := git.ToplevelDir(); err == nil {
			// TODO: figure out how to stub this in tests
			nonLegacyTemplateFiles = githubtemplate.FindNonLegacy(rootDir, "ISSUE_TEMPLATE")
		}
	}

	title, err := cmd.Flags().GetString("title")
	if err != nil {
		return fmt.Errorf("could not parse title: %w", err)
	}
	body, err := cmd.Flags().GetString("body")
	if err != nil {
		return fmt.Errorf("could not parse body: %w", err)
	}

	assignees, err := cmd.Flags().GetStringSlice("assignee")
	if err != nil {
		return fmt.Errorf("could not parse assignees: %w", err)
	}
	labelNames, err := cmd.Flags().GetStringSlice("label")
	if err != nil {
		return fmt.Errorf("could not parse labels: %w", err)
	}
	projectNames, err := cmd.Flags().GetStringSlice("project")
	if err != nil {
		return fmt.Errorf("could not parse projects: %w", err)
	}
	var milestoneTitles []string
	if milestoneTitle, err := cmd.Flags().GetString("milestone"); err != nil {
		return fmt.Errorf("could not parse milestone: %w", err)
	} else if milestoneTitle != "" {
		milestoneTitles = append(milestoneTitles, milestoneTitle)
	}

	if isWeb, err := cmd.Flags().GetBool("web"); err == nil && isWeb {
		// TODO: move URL generation into GitHubRepository
		openURL := fmt.Sprintf("https://github.com/%s/issues/new", ghrepo.FullName(baseRepo))
		if title != "" || body != "" {
			milestone := ""
			if len(milestoneTitles) > 0 {
				milestone = milestoneTitles[0]
			}
			openURL, err = withPrAndIssueQueryParams(openURL, title, body, assignees, labelNames, projectNames, milestone)
			if err != nil {
				return err
			}
		} else if len(nonLegacyTemplateFiles) > 1 {
			openURL += "/choose"
		}
		cmd.Printf("Opening %s in your browser.\n", displayURL(openURL))
		return utils.OpenInBrowser(openURL)
	}

	fmt.Fprintf(colorableErr(cmd), "\nCreating issue in %s\n\n", ghrepo.FullName(baseRepo))

	repo, err := api.GitHubRepo(apiClient, baseRepo)
	if err != nil {
		return err
	}
	if !repo.HasIssuesEnabled {
		return fmt.Errorf("the '%s' repository has disabled issues", ghrepo.FullName(baseRepo))
	}

	action := SubmitAction
	tb := issueMetadataState{
		Type:       issueMetadata,
		Assignees:  assignees,
		Labels:     labelNames,
		Projects:   projectNames,
		Milestones: milestoneTitles,
	}

	interactive := !(cmd.Flags().Changed("title") && cmd.Flags().Changed("body"))

	if interactive {
		var legacyTemplateFile *string
		if baseOverride == "" {
			if rootDir, err := git.ToplevelDir(); err == nil {
				// TODO: figure out how to stub this in tests
				legacyTemplateFile = githubtemplate.FindLegacy(rootDir, "ISSUE_TEMPLATE")
			}
		}
		err := titleBodySurvey(cmd, &tb, apiClient, baseRepo, title, body, defaults{}, nonLegacyTemplateFiles, legacyTemplateFile, false, repo.ViewerCanTriage())
		if err != nil {
			return fmt.Errorf("could not collect title and/or body: %w", err)
		}

		action = tb.Action

		if tb.Action == CancelAction {
			fmt.Fprintln(cmd.ErrOrStderr(), "Discarding.")

			return nil
		}

		if title == "" {
			title = tb.Title
		}
		if body == "" {
			body = tb.Body
		}
	} else {
		if title == "" {
			return fmt.Errorf("title can't be blank")
		}
	}

	if action == PreviewAction {
		openURL := fmt.Sprintf("https://github.com/%s/issues/new/", ghrepo.FullName(baseRepo))
		milestone := ""
		if len(milestoneTitles) > 0 {
			milestone = milestoneTitles[0]
		}
		openURL, err = withPrAndIssueQueryParams(openURL, title, body, assignees, labelNames, projectNames, milestone)
		if err != nil {
			return err
		}
		// TODO could exceed max url length for explorer
		fmt.Fprintf(cmd.ErrOrStderr(), "Opening %s in your browser.\n", displayURL(openURL))
		return utils.OpenInBrowser(openURL)
	} else if action == SubmitAction {
		params := map[string]interface{}{
			"title": title,
			"body":  body,
		}

		err = addMetadataToIssueParams(apiClient, baseRepo, params, &tb)
		if err != nil {
			return err
		}

		newIssue, err := api.IssueCreate(apiClient, repo, params)
		if err != nil {
			return err
		}

		fmt.Fprintln(cmd.OutOrStdout(), newIssue.URL)
	} else {
		panic("Unreachable state")
	}

	return nil
}

func addMetadataToIssueParams(client *api.Client, baseRepo ghrepo.Interface, params map[string]interface{}, tb *issueMetadataState) error {
	if !tb.HasMetadata() {
		return nil
	}

	if tb.MetadataResult == nil {
		resolveInput := api.RepoResolveInput{
			Reviewers:  tb.Reviewers,
			Assignees:  tb.Assignees,
			Labels:     tb.Labels,
			Projects:   tb.Projects,
			Milestones: tb.Milestones,
		}

		var err error
		tb.MetadataResult, err = api.RepoResolveMetadataIDs(client, baseRepo, resolveInput)
		if err != nil {
			return err
		}
	}

	assigneeIDs, err := tb.MetadataResult.MembersToIDs(tb.Assignees)
	if err != nil {
		return fmt.Errorf("could not assign user: %w", err)
	}
	params["assigneeIds"] = assigneeIDs

	labelIDs, err := tb.MetadataResult.LabelsToIDs(tb.Labels)
	if err != nil {
		return fmt.Errorf("could not add label: %w", err)
	}
	params["labelIds"] = labelIDs

	projectIDs, err := tb.MetadataResult.ProjectsToIDs(tb.Projects)
	if err != nil {
		return fmt.Errorf("could not add to project: %w", err)
	}
	params["projectIds"] = projectIDs

	if len(tb.Milestones) > 0 {
		milestoneID, err := tb.MetadataResult.MilestoneToID(tb.Milestones[0])
		if err != nil {
			return fmt.Errorf("could not add to milestone '%s': %w", tb.Milestones[0], err)
		}
		params["milestoneId"] = milestoneID
	}

	if len(tb.Reviewers) == 0 {
		return nil
	}

	var userReviewers []string
	var teamReviewers []string
	for _, r := range tb.Reviewers {
		if strings.ContainsRune(r, '/') {
			teamReviewers = append(teamReviewers, r)
		} else {
			userReviewers = append(userReviewers, r)
		}
	}

	userReviewerIDs, err := tb.MetadataResult.MembersToIDs(userReviewers)
	if err != nil {
		return fmt.Errorf("could not request reviewer: %w", err)
	}
	params["userReviewerIds"] = userReviewerIDs

	teamReviewerIDs, err := tb.MetadataResult.TeamsToIDs(teamReviewers)
	if err != nil {
		return fmt.Errorf("could not request reviewer: %w", err)
	}
	params["teamReviewerIds"] = teamReviewerIDs

	return nil
}

func printIssues(w io.Writer, prefix string, totalCount int, issues []api.Issue) {
	table := utils.NewTablePrinter(w)
	for _, issue := range issues {
		issueNum := strconv.Itoa(issue.Number)
		if table.IsTTY() {
			issueNum = "#" + issueNum
		}
		issueNum = prefix + issueNum
		labels := issueLabelList(issue)
		if labels != "" && table.IsTTY() {
			labels = fmt.Sprintf("(%s)", labels)
		}
		now := time.Now()
		ago := now.Sub(issue.UpdatedAt)
		table.AddField(issueNum, nil, colorFuncForState(issue.State))
		table.AddField(replaceExcessiveWhitespace(issue.Title), nil, nil)
		table.AddField(labels, nil, utils.Gray)
		table.AddField(utils.FuzzyAgo(ago), nil, utils.Gray)
		table.EndRow()
	}
	_ = table.Render()
	remaining := totalCount - len(issues)
	if remaining > 0 {
		fmt.Fprintf(w, utils.Gray("%sAnd %d more\n"), prefix, remaining)
	}
}

func issueAssigneeList(issue api.Issue) string {
	if len(issue.Assignees.Nodes) == 0 {
		return ""
	}

	AssigneeNames := make([]string, 0, len(issue.Assignees.Nodes))
	for _, assignee := range issue.Assignees.Nodes {
		AssigneeNames = append(AssigneeNames, assignee.Login)
	}

	list := strings.Join(AssigneeNames, ", ")
	if issue.Assignees.TotalCount > len(issue.Assignees.Nodes) {
		list += ", …"
	}
	return list
}

func issueLabelList(issue api.Issue) string {
	if len(issue.Labels.Nodes) == 0 {
		return ""
	}

	labelNames := make([]string, 0, len(issue.Labels.Nodes))
	for _, label := range issue.Labels.Nodes {
		labelNames = append(labelNames, label.Name)
	}

	list := strings.Join(labelNames, ", ")
	if issue.Labels.TotalCount > len(issue.Labels.Nodes) {
		list += ", …"
	}
	return list
}

func issueProjectList(issue api.Issue) string {
	if len(issue.ProjectCards.Nodes) == 0 {
		return ""
	}

	projectNames := make([]string, 0, len(issue.ProjectCards.Nodes))
	for _, project := range issue.ProjectCards.Nodes {
		colName := project.Column.Name
		if colName == "" {
			colName = "Awaiting triage"
		}
		projectNames = append(projectNames, fmt.Sprintf("%s (%s)", project.Project.Name, colName))
	}

	list := strings.Join(projectNames, ", ")
	if issue.ProjectCards.TotalCount > len(issue.ProjectCards.Nodes) {
		list += ", …"
	}
	return list
}

func issueClose(cmd *cobra.Command, args []string) error {
	ctx := contextForCommand(cmd)
	apiClient, err := apiClientForContext(ctx)
	if err != nil {
		return err
	}

	baseRepo, err := determineBaseRepo(apiClient, cmd, ctx)
	if err != nil {
		return err
	}

	issue, err := issueFromArg(apiClient, baseRepo, args[0])
	var idErr *api.IssuesDisabledError
	if errors.As(err, &idErr) {
		return fmt.Errorf("issues disabled for %s", ghrepo.FullName(baseRepo))
	} else if err != nil {
		return fmt.Errorf("failed to find issue #%d: %w", issue.Number, err)
	}

	if issue.Closed {
		fmt.Fprintf(colorableErr(cmd), "%s Issue #%d is already closed\n", utils.Yellow("!"), issue.Number)
		return nil
	}

	err = api.IssueClose(apiClient, baseRepo, *issue)
	if err != nil {
		return fmt.Errorf("API call failed:%w", err)
	}

	fmt.Fprintf(colorableErr(cmd), "%s Closed issue #%d\n", utils.Red("✔"), issue.Number)

	return nil
}

func issueReopen(cmd *cobra.Command, args []string) error {
	ctx := contextForCommand(cmd)
	apiClient, err := apiClientForContext(ctx)
	if err != nil {
		return err
	}

	baseRepo, err := determineBaseRepo(apiClient, cmd, ctx)
	if err != nil {
		return err
	}

	issue, err := issueFromArg(apiClient, baseRepo, args[0])
	var idErr *api.IssuesDisabledError
	if errors.As(err, &idErr) {
		return fmt.Errorf("issues disabled for %s", ghrepo.FullName(baseRepo))
	} else if err != nil {
		return fmt.Errorf("failed to find issue #%d: %w", issue.Number, err)
	}

	if !issue.Closed {
		fmt.Fprintf(colorableErr(cmd), "%s Issue #%d is already open\n", utils.Yellow("!"), issue.Number)
		return nil
	}

	err = api.IssueReopen(apiClient, baseRepo, *issue)
	if err != nil {
		return fmt.Errorf("API call failed:%w", err)
	}

	fmt.Fprintf(colorableErr(cmd), "%s Reopened issue #%d\n", utils.Green("✔"), issue.Number)

	return nil
}

func displayURL(urlStr string) string {
	u, err := url.Parse(urlStr)
	if err != nil {
		return urlStr
	}
	return u.Hostname() + u.Path
}