package create

import (
	"context"
	"errors"
	"fmt"
	"net/url"
	"strings"
	"time"

	"github.com/cenkalti/backoff/v4"

	"github.com/MakeNowJust/heredoc"
	"github.com/cli/cli/v2/internal/gh"
	"github.com/cli/cli/v2/internal/ghrepo"
	"github.com/cli/cli/v2/internal/prompter"
	"github.com/cli/cli/v2/pkg/cmd/agent-task/capi"
	"github.com/cli/cli/v2/pkg/cmd/agent-task/shared"
	"github.com/cli/cli/v2/pkg/cmdutil"
	"github.com/cli/cli/v2/pkg/iostreams"
	"github.com/spf13/cobra"
)

// CreateOptions holds options for create command
type CreateOptions struct {
	IO               *iostreams.IOStreams
	BaseRepo         func() (ghrepo.Interface, error)
	CapiClient       func() (capi.CapiClient, error)
	Config           func() (gh.Config, error)
	ProblemStatement string
	BackOff          backoff.BackOff
	BaseBranch       string
	Prompter         prompter.Prompter
}

func NewCmdCreate(f *cmdutil.Factory, runF func(*CreateOptions) error) *cobra.Command {
	opts := &CreateOptions{
		IO:         f.IOStreams,
		CapiClient: shared.CapiClientFunc(f),
		Config:     f.Config,
		Prompter:   f.Prompter,
	}

	var fromFileName string

	cmd := &cobra.Command{
		Use:   "create [<task description>] [flags]",
		Short: "Create an agent task (preview)",
		Args:  cobra.MaximumNArgs(1),
		RunE: func(cmd *cobra.Command, args []string) error {
			// Support -R/--repo override
			opts.BaseRepo = f.BaseRepo

			if err := cmdutil.MutuallyExclusive("only one of -F or arg can be provided", len(args) > 0, fromFileName != ""); err != nil {
				return err
			}

			// Gather arg inputs for ProblemStatement
			if len(args) > 0 {
				opts.ProblemStatement = args[0]
			} else if fromFileName != "" {
				fileContent, err := cmdutil.ReadFile(fromFileName, opts.IO.In)
				if err != nil {
					return cmdutil.FlagErrorf("could not read task description file: %v", err)
				}
				trimmed := strings.TrimSpace(string(fileContent))
				if trimmed == "" {
					return cmdutil.FlagErrorf("task description file is empty")
				}
				opts.ProblemStatement = trimmed
			}

			if runF != nil {
				return runF(opts)
			}
			return createRun(opts)
		},
		Example: heredoc.Doc(`
			# Create a task from an inline description
			$ gh agent-task create "build me a new app"

			# Create a task from a file
			$ gh agent-task create -F task-desc.md

			# Create a task with problem statement from stdin
			$ echo "build me a new app" | gh agent-task create -F -

			# Create a task with an editor prompt (interactive)
			$ gh agent-task create

			# Select a different base branch for the PR
			$ gh agent-task create "fix errors" --base branch
		`),
	}

	cmdutil.EnableRepoOverride(cmd, f)

	cmd.Flags().StringVarP(&fromFileName, "from-file", "F", "", "Read task description from `file` (use \"-\" to read from standard input)")
	cmd.Flags().StringVarP(&opts.BaseBranch, "base", "b", "", "Base branch for the pull request (use default branch if not provided)")

	return cmd
}

func createRun(opts *CreateOptions) error {
	repo, err := opts.BaseRepo()
	if err != nil || repo == nil {
		// Not printing the error that came back from BaseRepo() here because we want
		// something clear, human friendly, and actionable.
		return fmt.Errorf("a repository is required; re-run in a repository or supply one with --repo owner/name")
	}

	if opts.ProblemStatement == "" {
		if !opts.IO.CanPrompt() {
			return cmdutil.FlagErrorf("a task description or -F is required when running non-interactively")
		}

		desc, err := opts.Prompter.MarkdownEditor("Enter the task description", opts.ProblemStatement, false)
		if err != nil {
			return err
		}

		trimmed := strings.TrimSpace(desc)
		if trimmed == "" {
			return cmdutil.FlagErrorf("a task description is required")
		}
		opts.ProblemStatement = trimmed
	}

	client, err := opts.CapiClient()
	if err != nil {
		return err
	}

	ctx := context.Background()
	opts.IO.StartProgressIndicatorWithLabel(fmt.Sprintf("Creating agent task in %s/%s...", repo.RepoOwner(), repo.RepoName()))
	defer opts.IO.StopProgressIndicator()

	job, err := client.CreateJob(ctx, repo.RepoOwner(), repo.RepoName(), opts.ProblemStatement, opts.BaseBranch)
	if err != nil {
		return err
	}

	// Print this agent session URL and exit if we happen to get it.
	// Right now, this never happens.
	if job.PullRequest != nil && job.PullRequest.Number > 0 {
		fmt.Fprintf(opts.IO.Out, "%s\n", agentSessionWebURL(repo, job))
		return nil
	}

	// Otherwise, poll using exponential backoff until we either observe a PR or hit the overall timeout.
	if opts.BackOff == nil {
		opts.BackOff = backoff.NewExponentialBackOff(
			backoff.WithMaxElapsedTime(10*time.Second),
			backoff.WithInitialInterval(300*time.Millisecond),
			backoff.WithMaxInterval(10*time.Second),
			backoff.WithMultiplier(1.5),
		)
	}

	jobWithPR, err := fetchJobWithBackoff(ctx, client, repo, job.ID, opts.BackOff)
	if err != nil {
		// If this does happen ever, we still want the user to get the
		// fallback message and URL. So, we don't return with this error,
		// but we do still want to print it.
		fmt.Fprintf(opts.IO.ErrOut, "%v\n", err)
	}

	if jobWithPR != nil {
		opts.IO.StopProgressIndicator()
		fmt.Fprintln(opts.IO.Out, agentSessionWebURL(repo, jobWithPR))
		return nil
	}

	// Fallback if PR not yet ready
	opts.IO.StopProgressIndicator()
	fmt.Fprintf(opts.IO.Out, "job %s queued. View progress: https://github.com/copilot/agents\n", job.ID)
	return nil
}

func agentSessionWebURL(repo ghrepo.Interface, j *capi.Job) string {
	if j.PullRequest == nil {
		return ""
	}
	if j.SessionID == "" {
		return fmt.Sprintf("https://github.com/%s/%s/pull/%d", url.PathEscape(repo.RepoOwner()), url.PathEscape(repo.RepoName()), j.PullRequest.Number)
	}
	return fmt.Sprintf("https://github.com/%s/%s/pull/%d/agent-sessions/%s", url.PathEscape(repo.RepoOwner()), url.PathEscape(repo.RepoName()), j.PullRequest.Number, url.PathEscape(j.SessionID))
}

// fetchJobWithBackoff polls the job resource until a PR number is present or the overall
// timeout elapses. It returns the updated Job on success, (nil, nil) on timeout,
// and (nil, error) only for non-retryable failures.
func fetchJobWithBackoff(ctx context.Context, client capi.CapiClient, repo ghrepo.Interface, jobID string, bo backoff.BackOff) (*capi.Job, error) {
	// sentinel error to signal timeout
	var errPRNotReady = errors.New("job not ready")

	var result *capi.Job
	retryErr := backoff.Retry(func() error {
		j, err := client.GetJob(ctx, repo.RepoOwner(), repo.RepoName(), jobID)
		if err != nil {
			// Do not retry on GetJob errors; surface immediately.
			return backoff.Permanent(err)
		}
		if j.PullRequest != nil && j.PullRequest.Number > 0 {
			result = j
			return nil
		}
		return errPRNotReady
	}, backoff.WithContext(bo, ctx))

	if retryErr != nil {
		if errors.Is(retryErr, errPRNotReady) {
			// Timed out
			return nil, nil
		}
		return nil, retryErr
	}
	return result, nil
}