package command

import (
	"fmt"
	"io"
	"regexp"
	"strconv"
	"strings"

	"github.com/cli/cli/api"
	"github.com/cli/cli/context"
	"github.com/cli/cli/git"
	"github.com/cli/cli/internal/ghrepo"
	"github.com/cli/cli/utils"
	"github.com/spf13/cobra"
	"github.com/spf13/pflag"
)

func init() {
	RootCmd.AddCommand(prCmd)
	prCmd.AddCommand(prCheckoutCmd)
	prCmd.AddCommand(prCreateCmd)
	prCmd.AddCommand(prListCmd)
	prCmd.AddCommand(prStatusCmd)
	prCmd.AddCommand(prViewCmd)

	prListCmd.Flags().IntP("limit", "L", 30, "Maximum number of items to fetch")
	prListCmd.Flags().StringP("state", "s", "open", "Filter by state: {open|closed|merged|all}")
	prListCmd.Flags().StringP("base", "B", "", "Filter by base branch")
	prListCmd.Flags().StringSliceP("label", "l", nil, "Filter by label")
	prListCmd.Flags().StringP("assignee", "a", "", "Filter by assignee")
	prListCmd.Flags().BoolP("self", "S", false, "Query current repository instead of forked parent")

	prViewCmd.Flags().BoolP("preview", "p", false, "Display preview of pull request content")
	prViewCmd.Flags().BoolP("self", "S", false, "Query current repository instead of forked parent")

	prStatusCmd.Flags().BoolP("self", "S", false, "Query current repository instead of forked parent")
}

var prCmd = &cobra.Command{
	Use:   "pr",
	Short: "Create, view, and checkout pull requests",
	Long: `Work with GitHub pull requests.

A pull request can be supplied as argument in any of the following formats:
- by number, e.g. "123";
- by URL, e.g. "https://github.com/OWNER/REPO/pull/123"; or
- by the name of its head branch, e.g. "patch-1" or "OWNER:patch-1".`,
}
var prListCmd = &cobra.Command{
	Use:   "list",
	Short: "List and filter pull requests in this repository",
	RunE:  prList,
}
var prStatusCmd = &cobra.Command{
	Use:   "status",
	Short: "Show status of relevant pull requests",
	RunE:  prStatus,
}
var prViewCmd = &cobra.Command{
	Use:   "view [{<number> | <url> | <branch>}]",
	Short: "View a pull request in the browser",
	Long: `View a pull request specified by the argument in the browser.

Without an argument, the pull request that belongs to the current
branch is opened.`,
	RunE: prView,
}

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

	referSelf, _ := cmd.Flags().GetBool("self")
	if referSelf == false {
		ctx = context.ExpandOnline(ctx, apiClient)
	}

	baseRepo, err := context.DetermineRepo(ctx, referSelf)
	if err != nil {
		return err
	}
	currentPRNumber, currentPRHeadRef, err := prSelectorForCurrentBranch(ctx)
	if err != nil {
		return err
	}
	currentUser, err := ctx.AuthLogin()
	if err != nil {
		return err
	}

	prPayload, err := api.PullRequests(apiClient, baseRepo, currentPRNumber, currentPRHeadRef, currentUser)
	if err != nil {
		return err
	}

	out := colorableOut(cmd)

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

	printHeader(out, "Current branch")
	if prPayload.CurrentPR != nil {
		printPrs(out, 0, *prPayload.CurrentPR)
	} else {
		message := fmt.Sprintf("  There is no pull request associated with %s", utils.Cyan("["+currentPRHeadRef+"]"))
		printMessage(out, message)
	}
	fmt.Fprintln(out)

	printHeader(out, "Created by you")
	if prPayload.ViewerCreated.TotalCount > 0 {
		printPrs(out, prPayload.ViewerCreated.TotalCount, prPayload.ViewerCreated.PullRequests...)
	} else {
		printMessage(out, "  You have no open pull requests")
	}
	fmt.Fprintln(out)

	printHeader(out, "Requesting a code review from you")
	if prPayload.ReviewRequested.TotalCount > 0 {
		printPrs(out, prPayload.ReviewRequested.TotalCount, prPayload.ReviewRequested.PullRequests...)
	} else {
		printMessage(out, "  You have no pull requests to review")
	}
	fmt.Fprintln(out)

	return nil
}

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

	referSelf, _ := cmd.Flags().GetBool("self")
	if referSelf == false {
		ctx = context.ExpandOnline(ctx, apiClient)
	}

	baseRepo, err := context.DetermineRepo(ctx, referSelf)
	if err != nil {
		return err
	}

	fmt.Fprintf(colorableErr(cmd), "\nPull requests for %s\n\n", ghrepo.FullName(baseRepo))

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

	var graphqlState []string
	switch state {
	case "open":
		graphqlState = []string{"OPEN"}
	case "closed":
		graphqlState = []string{"CLOSED"}
	case "merged":
		graphqlState = []string{"MERGED"}
	case "all":
		graphqlState = []string{"OPEN", "CLOSED", "MERGED"}
	default:
		return fmt.Errorf("invalid state: %s", state)
	}

	params := map[string]interface{}{
		"owner": baseRepo.RepoOwner(),
		"repo":  baseRepo.RepoName(),
		"state": graphqlState,
	}
	if len(labels) > 0 {
		params["labels"] = labels
	}
	if baseBranch != "" {
		params["baseBranch"] = baseBranch
	}
	if assignee != "" {
		params["assignee"] = assignee
	}

	prs, err := api.PullRequestList(apiClient, params, limit)
	if err != nil {
		return err
	}

	if len(prs) == 0 {
		colorErr := colorableErr(cmd) // Send to stderr because otherwise when piping this command it would seem like the "no open prs" message is acually a pr
		msg := "There are no open pull requests"

		userSetFlags := false
		cmd.Flags().Visit(func(f *pflag.Flag) {
			userSetFlags = true
		})
		if userSetFlags {
			msg = "No pull requests match your search"
		}
		printMessage(colorErr, msg)
		return nil
	}

	table := utils.NewTablePrinter(cmd.OutOrStdout())
	for _, pr := range prs {
		prNum := strconv.Itoa(pr.Number)
		if table.IsTTY() {
			prNum = "#" + prNum
		}
		table.AddField(prNum, nil, colorFuncForState(pr.State))
		table.AddField(replaceExcessiveWhitespace(pr.Title), nil, nil)
		table.AddField(pr.HeadLabel(), nil, utils.Cyan)
		table.EndRow()
	}
	err = table.Render()
	if err != nil {
		return err
	}

	return nil
}

func colorFuncForState(state string) func(string) string {
	switch state {
	case "OPEN":
		return utils.Green
	case "CLOSED":
		return utils.Red
	case "MERGED":
		return utils.Magenta
	default:
		return nil
	}
}

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

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

	referSelf, _ := cmd.Flags().GetBool("self")
	if referSelf == false {
		ctx = context.ExpandOnline(ctx, apiClient)
	}

	baseRepo, err := context.DetermineRepo(ctx, referSelf)
	if err != nil {
		return err
	}

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

	var openURL string
	var pr *api.PullRequest
	if len(args) > 0 {
		pr, err = prFromArg(apiClient, baseRepo, args[0])
		if err != nil {
			return err
		}
		openURL = pr.URL
	} else {
		prNumber, branchWithOwner, err := prSelectorForCurrentBranch(ctx)
		if err != nil {
			return err
		}

		if prNumber > 0 {
			openURL = fmt.Sprintf("https://github.com/%s/pull/%d", ghrepo.FullName(baseRepo), prNumber)
			if preview {
				pr, err = api.PullRequestByNumber(apiClient, baseRepo, prNumber)
				if err != nil {
					return err
				}
			}
		} else {
			pr, err = api.PullRequestForBranch(apiClient, baseRepo, branchWithOwner)
			if err != nil {
				return err
			}

			openURL = pr.URL
		}
	}

	if preview {
		out := colorableOut(cmd)
		printPrPreview(out, pr)
		return nil
	} else {
		fmt.Fprintf(cmd.ErrOrStderr(), "Opening %s in your browser.\n", openURL)
		return utils.OpenInBrowser(openURL)
	}
}

func printPrPreview(out io.Writer, pr *api.PullRequest) {
	fmt.Fprintln(out, utils.Bold(pr.Title))
	fmt.Fprintln(out, utils.Gray(fmt.Sprintf(
		"%s wants to merge %s into %s from %s",
		pr.Author.Login,
		utils.Pluralize(pr.Commits.TotalCount, "commit"),
		pr.BaseRefName,
		pr.HeadRefName,
	)))
	fmt.Fprintln(out)
	fmt.Fprintln(out, utils.RenderMarkdown(pr.Body))
	fmt.Fprintln(out)
	fmt.Fprintf(out, utils.Gray("View this pull request on GitHub: %s\n"), pr.URL)
}

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

func prFromArg(apiClient *api.Client, baseRepo ghrepo.Interface, arg string) (*api.PullRequest, error) {
	if prNumber, err := strconv.Atoi(arg); err == nil {
		return api.PullRequestByNumber(apiClient, baseRepo, prNumber)
	}

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

	return api.PullRequestForBranch(apiClient, baseRepo, arg)
}

func prSelectorForCurrentBranch(ctx context.Context) (prNumber int, prHeadRef string, err error) {
	baseRepo, err := ctx.BaseRepo()
	if err != nil {
		return
	}
	prHeadRef, err = ctx.Branch()
	if err != nil {
		return
	}
	branchConfig := git.ReadBranchConfig(prHeadRef)

	// the branch is configured to merge a special PR head ref
	prHeadRE := regexp.MustCompile(`^refs/pull/(\d+)/head$`)
	if m := prHeadRE.FindStringSubmatch(branchConfig.MergeRef); m != nil {
		prNumber, _ = strconv.Atoi(m[1])
		return
	}

	var branchOwner string
	if branchConfig.RemoteURL != nil {
		// the branch merges from a remote specified by URL
		if r, err := ghrepo.FromURL(branchConfig.RemoteURL); err == nil {
			branchOwner = r.RepoOwner()
		}
	} else if branchConfig.RemoteName != "" {
		// the branch merges from a remote specified by name
		rem, _ := ctx.Remotes()
		if r, err := rem.FindByName(branchConfig.RemoteName); err == nil {
			branchOwner = r.RepoOwner()
		}
	}

	if branchOwner != "" {
		if strings.HasPrefix(branchConfig.MergeRef, "refs/heads/") {
			prHeadRef = strings.TrimPrefix(branchConfig.MergeRef, "refs/heads/")
		}
		// prepend `OWNER:` if this branch is pushed to a fork
		if !strings.EqualFold(branchOwner, baseRepo.RepoOwner()) {
			prHeadRef = fmt.Sprintf("%s:%s", branchOwner, prHeadRef)
		}
	}

	return
}

func printPrs(w io.Writer, totalCount int, prs ...api.PullRequest) {
	for _, pr := range prs {
		prNumber := fmt.Sprintf("#%d", pr.Number)
		fmt.Fprintf(w, "  %s  %s %s", utils.Green(prNumber), truncate(50, replaceExcessiveWhitespace(pr.Title)), utils.Cyan("["+pr.HeadLabel()+"]"))

		checks := pr.ChecksStatus()
		reviews := pr.ReviewStatus()
		if checks.Total > 0 || reviews.ChangesRequested || reviews.Approved {
			fmt.Fprintf(w, "\n  ")
		}

		if checks.Total > 0 {
			var summary string
			if checks.Failing > 0 {
				if checks.Failing == checks.Total {
					summary = utils.Red("All checks failing")
				} else {
					summary = utils.Red(fmt.Sprintf("%d/%d checks failing", checks.Failing, checks.Total))
				}
			} else if checks.Pending > 0 {
				summary = utils.Yellow("Checks pending")
			} else if checks.Passing == checks.Total {
				summary = utils.Green("Checks passing")
			}
			fmt.Fprintf(w, " - %s", summary)
		}

		if reviews.ChangesRequested {
			fmt.Fprintf(w, " - %s", utils.Red("Changes requested"))
		} else if reviews.ReviewRequired {
			fmt.Fprintf(w, " - %s", utils.Yellow("Review required"))
		} else if reviews.Approved {
			fmt.Fprintf(w, " - %s", utils.Green("Approved"))
		}

		fmt.Fprint(w, "\n")
	}
	remaining := totalCount - len(prs)
	if remaining > 0 {
		fmt.Fprintf(w, utils.Gray("  And %d more\n"), remaining)
	}
}

func printHeader(w io.Writer, s string) {
	fmt.Fprintln(w, utils.Bold(s))
}

func printMessage(w io.Writer, s string) {
	fmt.Fprintln(w, utils.Gray(s))
}

func truncate(maxLength int, title string) string {
	if len(title) > maxLength {
		return title[0:maxLength-3] + "..."
	}
	return title
}

func replaceExcessiveWhitespace(s string) string {
	s = strings.TrimSpace(s)
	s = regexp.MustCompile(`\r?\n`).ReplaceAllString(s, " ")
	s = regexp.MustCompile(`\s{2,}`).ReplaceAllString(s, " ")
	return s
}