// Package tui provides an interactive terminal UI for browsing gitflow scan
// results using bubbletea.
package tui

import (
	"context"
	"fmt"
	"strings"
	"time"

	"github.com/charmbracelet/bubbletea"

	"gitea.oblak.solutions/dimitar/gitFlow/internal/ai"
	"gitea.oblak.solutions/dimitar/gitFlow/internal/app"
	"gitea.oblak.solutions/dimitar/gitFlow/internal/config"
	"gitea.oblak.solutions/dimitar/gitFlow/internal/presenter"
	"gitea.oblak.solutions/dimitar/gitFlow/pkg/status"
)

// Model is the top-level bubbletea model for the TUI.
type Model struct {
	app  *app.App
	ai   ai.Provider // nil when AI is disabled
	cfg  *config.Config
	opts presenter.Options

	result     status.ScanResult
	prevResult status.ScanResult
	cursor     int
	detail     bool
	help       bool
	aiPanel    bool

	width  int
	height int

	loading   bool
	aiLoading bool
	err       string
	first     bool

	interval time.Duration
	lastScan time.Time
	changed  map[string]bool // repo paths whose state changed since previous scan

	styles Styles
}

// New builds a bubbletea Program for the TUI. It runs an initial scan
// synchronously so the first frame shows results immediately.
func New(cfg *config.Config, a *app.App, aiProvider ai.Provider, opts presenter.Options) (*tea.Program, error) {
	result, err := a.ScanOnce(context.Background())
	if err != nil {
		return nil, fmt.Errorf("tui: initial scan: %w", err)
	}
	return newProgram(cfg, a, aiProvider, opts, result, false), nil
}

func newProgram(cfg *config.Config, a *app.App, aiProvider ai.Provider, opts presenter.Options, result status.ScanResult, loading bool) *tea.Program {
	m := Model{
		app:      a,
		ai:       aiProvider,
		cfg:      cfg,
		opts:     opts,
		result:   result,
		cursor:   0,
		detail:   false,
		first:    true,
		interval: cfg.Interval,
		lastScan: time.Now(),
		changed:  map[string]bool{},
		styles:   NewStyles(opts),
	}
	if loading {
		m.loading = true
	}
	return tea.NewProgram(m, tea.WithAltScreen())
}

// Init is the initial command.
func (m Model) Init() tea.Cmd {
	if m.loading {
		return m.scanCmd
	}
	if m.interval > 0 {
		return tea.Tick(m.interval, func(t time.Time) tea.Msg {
			return scanTickMsg{t}
		})
	}
	return nil
}

// scanTickMsg is sent by the ticker every interval.
type scanTickMsg struct{ at time.Time }

// scanResultMsg carries a completed scan.
type scanResultMsg struct{ result status.ScanResult }

// scanErrorMsg carries a failed scan.
type scanErrorMsg struct{ err error }

// scanCmd triggers a scan in the background.
func (m Model) scanCmd() tea.Msg {
	result, err := m.app.ScanOnce(context.Background())
	if err != nil {
		return scanErrorMsg{err}
	}
	return scanResultMsg{result}
}

// ---- update ----------------------------------------------------------------

// Update handles incoming messages.
func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
	switch msg := msg.(type) {
	case tea.WindowSizeMsg:
		m.width = msg.Width
		m.height = msg.Height

	case tea.KeyMsg:
		switch msg.String() {
		case "ctrl+c", "q":
			return m, tea.Quit
		case "?":
			m.help = !m.help
		case "down", "j":
			if m.cursor < len(m.result.Repos)-1 {
				m.cursor++
			}
		case "up", "k":
			if m.cursor > 0 {
				m.cursor--
			}
		case "home", "g":
			m.cursor = 0
		case "end", "G":
			if n := len(m.result.Repos); n > 0 {
				m.cursor = n - 1
			}
		case "enter", " ":
			m.detail = !m.detail
		case "r":
			if !m.loading {
				m.loading = true
				return m, m.scanCmd
			}
		}

	case scanTickMsg:
		if !m.loading {
			m.loading = true
			return m, m.scanCmd
		}
		if m.interval > 0 {
			return m, tea.Tick(m.interval, func(t time.Time) tea.Msg {
				return scanTickMsg{t}
			})
		}

	case scanResultMsg:
		if !m.first {
			m.prevResult = m.result
			m.changed = make(map[string]bool, len(msg.result.Repos))
			for _, r := range status.Changed(m.prevResult, msg.result) {
				m.changed[r.Path] = true
			}
		}
		m.result = msg.result
		m.loading = false
		m.err = ""
		m.lastScan = time.Now()
		if m.first {
			m.first = false
		}
		if m.interval > 0 {
			return m, tea.Tick(m.interval, func(t time.Time) tea.Msg {
				return scanTickMsg{t}
			})
		}

	case scanErrorMsg:
		m.err = msg.err.Error()
		m.loading = false
		m.lastScan = time.Now()
		if m.interval > 0 {
			return m, tea.Tick(m.interval, func(t time.Time) tea.Msg {
				return scanTickMsg{t}
			})
		}
	}
	return m, nil
}

// ---- view ------------------------------------------------------------------

// View renders the full TUI.
func (m Model) View() string {
	if m.help {
		return m.helpView()
	}

	var b strings.Builder
	b.WriteString(m.repoListView())
	b.WriteString("\n")
	if m.detail && m.cursor < len(m.result.Repos) {
		b.WriteString(m.detailView(m.result.Repos[m.cursor]))
		b.WriteString("\n")
	}
	b.WriteString(m.statusBarView())
	return b.String()
}

// ---- repo list -------------------------------------------------------------

func (m Model) repoListView() string {
	if m.loading && m.first {
		return fmt.Sprintf("\n  %s scanning %s...\n", m.styles.Dim("⏳"), m.cfg.Dir)
	}
	if len(m.result.Repos) == 0 {
		return fmt.Sprintf("\n  %s\n", m.styles.Dim("no repositories found under "+m.cfg.Dir))
	}

	var b strings.Builder
	header := m.styles.Header
	fmt.Fprintf(&b, "%s%-5s %-30s %-15s %-10s %5s %6s\n%s",
		header.Render(""),
		header.Render("STATUS"),
		header.Render("REPOSITORY"),
		header.Render("BRANCH"),
		header.Render("AHEAD/BEHIND"),
		header.Render("CHGS"),
		header.Render("STASH"),
		header.Render(""),
	)

	for i, repo := range m.result.Repos {
		changed := m.changed[repo.Path]
		cursor := " "
		if i == m.cursor {
			cursor = ">"
		} else if changed {
			cursor = "▲"
		}

		ab := "-"
		if repo.AheadBy > 0 || repo.BehindBy > 0 {
			ab = fmt.Sprintf("%d/%d", repo.AheadBy, repo.BehindBy)
		}

		chs := "-"
		if n := repo.FileCount(); n > 0 {
			chs = fmt.Sprintf("%d", n)
		}

		stash := "-"
		if repo.StashCount > 0 {
			stash = fmt.Sprintf("%d", repo.StashCount)
		}

		line := fmt.Sprintf("%s %-5s %-30s %-15s %5s %6s %6s\n",
			cursor,
			presenter.StatusSymbolFor(repo.Status),
			truncate(shortPath(repo.Path), 29),
			truncate(repo.Branch, 14),
			ab,
			chs,
			stash,
		)
		line = m.colorLine(repo.Status, cursor, line)
		if changed && cursor != ">" {
			line = m.styles.Changed.Render(line)
		}

		if i == m.cursor {
			b.WriteString(m.styles.CursorRow.Render(line))
		} else {
			b.WriteString(m.styles.Row.Render(line))
		}
	}
	return b.String()
}

func (m Model) colorLine(s status.RepoStatus, cursor string, line string) string {
	switch s {
	case status.StatusError:
		return m.styles.Dim(line)
	}
	return line
}

// ---- detail view -----------------------------------------------------------

func (m Model) detailView(repo status.RepoInfo) string {
	var b strings.Builder
	w := m.width
	if w < 40 {
		w = 80
	}
	sep := m.styles.Dim(strings.Repeat("─", max(0, w-2)))
	b.WriteString(sep + "\n")
	line := fmt.Sprintf(" %s  branch: %s  |  remote: %s  |  ahead: %d  behind: %d",
		repo.Path, repo.Branch, truncate(repo.RemoteURL, 30), repo.AheadBy, repo.BehindBy)
	b.WriteString(m.styles.Dim(line) + "\n")
	d := fmt.Sprintf(" staged: %d  modified: %d  untracked: %d  stash: %d",
		len(repo.StagedFiles), len(repo.ModifiedFiles), len(repo.UntrackedFiles), repo.StashCount)
	b.WriteString(d + "\n")
	if repo.Error != "" {
		b.WriteString(m.styles.Err(repo.Error) + "\n")
	}
	if len(repo.StagedFiles) > 0 {
		b.WriteString(" staged:   " + strings.Join(repo.StagedFiles, ", ") + "\n")
	}
	if len(repo.ModifiedFiles) > 0 {
		b.WriteString(" modified: " + strings.Join(repo.ModifiedFiles, ", ") + "\n")
	}
	if len(repo.UntrackedFiles) > 0 {
		b.WriteString(" untracked: " + strings.Join(repo.UntrackedFiles, ", ") + "\n")
	}
	return b.String()
}

// ---- status bar ------------------------------------------------------------

func (m Model) statusBarView() string {
	s := m.result.Summary()
	left := fmt.Sprintf("%d repos | %d clean | %d need attention | %d errors",
		s.Total, s.Clean, s.Attention, s.Errored)
	if m.err != "" {
		left += " [error: " + m.err + "]"
	}
	if m.interval > 0 {
		elapsed := time.Since(m.lastScan).Round(time.Second)
		next := m.interval - elapsed
		if next < 0 {
			next = 0
		}
		left += fmt.Sprintf(" | next: %v", next)
	}
	if m.loading {
		left += " | scanning…"
	}
	right := "r refresh  ? help  q quit  ↑↓ nav  Enter detail"
	bar := left + strings.Repeat(" ", max(0, m.width-len(left)-len(right))) + right
	return m.styles.StatusBar.Render(bar)
}

// ---- help ------------------------------------------------------------------

func (m Model) helpView() string {
	return m.styles.Dim(
		"\n KEYBINDINGS\n" +
			"  ↑/↓ or j/k  g/G  navigate\n" +
			"  Enter / Space   toggle detail pane\n" +
			"  r               refresh now\n" +
			"  a               AI suggestions (requires --ai)\n" +
			"  ?               toggle this help\n" +
			"  q / Ctrl-C      quit\n",
	)
}

// ---- helpers ---------------------------------------------------------------

func shortPath(p string) string {
	return presenter.ShortPath(p)
}

func truncate(s string, n int) string {
	if len(s) <= n {
		return s
	}
	return s[:n-1] + "…"
}