// app.go wires together config loading, auth bootstrap, and the Bubble Tea program.
// It decides whether cached Twitch auth can be reused and, when needed,
// connects the interactive login flow to the TUI through auth update messages.
package app

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"os"
	"strings"
	"time"

	tea "github.com/charmbracelet/bubbletea"

	"parasocial/internal/auth"
	"parasocial/internal/config"
	"parasocial/internal/gql"
	"parasocial/internal/tui"
	"parasocial/internal/twitch"
)

// Run loads the application configuration and starts the terminal UI.
func Run(ctx context.Context) error {
	ctx, cancel := context.WithCancel(ctx)
	defer cancel()

	cfg, err := config.LoadDefault()
	if err != nil {
		return err
	}

	httpClient := &http.Client{Timeout: 30 * time.Second}
	authClient := auth.NewClient(httpClient)
	authPath := auth.DefaultPath()

	state, err := authClient.ReuseAuth(ctx, authPath)
	if err != nil {
		return err
	}

	program := tea.NewProgram(
		tui.New(tui.Options{
			Streamers: twitch.LoadingStreamerEntries(cfg.Streamers),
			AuthState: state,
			StartAuth: func(ch chan<- tui.AuthUpdate) {
				go func() {
					defer close(ch)

					state, err := authClient.EnsureAuth(ctx, authPath, func(line string) {
						ch <- tui.AuthUpdate{Line: strings.TrimRight(line, "\n")}
					})
					if err != nil {
						ch <- tui.AuthUpdate{
							Line: fmt.Sprintf("Authentication failed: %v", err),
							Err:  err,
							Done: true,
						}
						return
					}

					ch <- tui.AuthUpdate{State: state, Done: true}
				}()
			},
			StartResolve: func(state *auth.State, ch chan<- tui.StreamerUpdate) {
				go func() {
					defer close(ch)

					service, err := newTwitchService(httpClient, state)
					if err != nil {
						ch <- tui.StreamerUpdate{Err: err, Done: true}
						return
					}
					if err := resolveStreamerEntries(ctx, service, cfg.Streamers, func(update tui.StreamerUpdate) {
						ch <- update
					}); err != nil {
						if errors.Is(err, context.Canceled) {
							return
						}
						ch <- tui.StreamerUpdate{Err: err, Done: true}
						return
					}
					ch <- tui.StreamerUpdate{Done: true}
				}()
			},
		}),
		tea.WithContext(ctx),
		tea.WithInput(os.Stdin),
		tea.WithOutput(os.Stdout),
	)
	_, err = program.Run()
	return err
}

// streamerService captures the Twitch lookups the app needs during UI resolution.
type streamerService interface {
	CurrentUser(context.Context) (*twitch.Viewer, error)
	ResolveStreamer(context.Context, string) (*twitch.Channel, error)
}

// newTwitchService builds a Twitch service from the authenticated session state.
func newTwitchService(httpClient *http.Client, state *auth.State) (*twitch.Service, error) {
	client := &gql.Client{
		HTTPClient: httpClient,
		Session: gql.Session{
			AccessToken: state.AccessToken,
			ClientID:    state.ClientID,
			DeviceID:    state.DeviceID,
			UserAgent:   auth.TVUserAgent(),
		},
	}
	if err := client.Validate(); err != nil {
		return nil, fmt.Errorf("configure graphql session: %w", err)
	}
	return &twitch.Service{GQL: client}, nil
}

// resolveStreamerEntries streams viewer and streamer resolution results into the TUI.
func resolveStreamerEntries(ctx context.Context, service streamerService, logins []string, send func(tui.StreamerUpdate)) error {
	viewer, err := service.CurrentUser(ctx)
	if err != nil {
		return fmt.Errorf("resolve current user: %w", err)
	}
	send(tui.StreamerUpdate{Viewer: viewer})

	for index, login := range logins {
		entry := twitch.StreamerEntry{
			ConfigLogin: login,
			Status:      twitch.StreamerLoading,
		}

		channel, err := service.ResolveStreamer(ctx, login)
		switch {
		case err == nil:
			entry.Login = channel.Login
			entry.ChannelID = channel.ID
			entry.Status = twitch.StreamerReady
		case errors.Is(err, context.Canceled):
			return err
		default:
			entry.Status = twitch.StreamerError
			entry.Error = err.Error()
		}

		send(tui.StreamerUpdate{
			Index: index,
			Entry: &entry,
		})
	}

	return nil
}