package main

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"unicode"

	tea "github.com/charmbracelet/bubbletea"
	"github.com/mattn/go-runewidth"

	"todoapp/internal/todos"
)

type model struct {
	project   string
	todosDir  string
	items     []todos.Todo
	warnings  []error
	query     string
	search    bool
	selected  int // index into the filtered list
	detail    bool
	scroll    int
	width     int
	height    int
	editor    *editor
	confirm   string
	confirmID string
	notice    string
}

func newModel(project string) (model, error) {
	absolute, err := filepath.Abs(project)
	if err != nil {
		return model{}, fmt.Errorf("resolve project directory %q: %w", project, err)
	}
	info, err := os.Stat(absolute)
	if err != nil {
		return model{}, fmt.Errorf("project directory %q: %w", absolute, err)
	}
	if !info.IsDir() {
		return model{}, fmt.Errorf("project path %q is not a directory", absolute)
	}
	dir := todos.Dir(absolute)
	items, warnings, err := todos.Scan(dir)
	if err != nil {
		return model{}, fmt.Errorf("load todos: %w", err)
	}
	return model{project: absolute, todosDir: dir, items: items, warnings: warnings, width: 80, height: 24}, nil
}

func (m model) Init() tea.Cmd { return nil }

func (m model) filtered() []int {
	query := strings.ToLower(strings.TrimSpace(m.query))
	var matches []int
	for i, todo := range m.items {
		haystack := strings.ToLower(strings.Join([]string{todo.ID, todo.Title, todo.Status, strings.Join(todo.Tags, " "), todo.Body}, " "))
		if query == "" || strings.Contains(haystack, query) {
			matches = append(matches, i)
		}
	}
	return matches
}

func (m *model) clampSelection() {
	matches := m.filtered()
	if len(matches) == 0 {
		m.selected = 0
	} else if m.selected >= len(matches) {
		m.selected = len(matches) - 1
	}
}

func (m model) Update(message tea.Msg) (tea.Model, tea.Cmd) {
	switch msg := message.(type) {
	case tea.WindowSizeMsg:
		m.width, m.height = msg.Width, msg.Height
		return m, nil
	case tea.KeyMsg:
		if msg.String() == "ctrl+c" {
			return m, tea.Quit
		}
		if m.confirm != "" {
			m.handleConfirm(msg)
			return m, nil
		}
		if m.editor != nil {
			m.handleEditor(msg)
			return m, nil
		}
		if m.search {
			switch msg.String() {
			case "esc", "enter":
				m.search = false
			case "backspace", "ctrl+h":
				runes := []rune(m.query)
				if len(runes) > 0 {
					m.query = string(runes[:len(runes)-1])
				}
				m.selected = 0
			case "ctrl+u":
				m.query = ""
				m.selected = 0
			default:
				if msg.Type == tea.KeySpace {
					m.query += " "
					m.selected = 0
				} else if msg.Type == tea.KeyRunes {
					m.query += string(msg.Runes)
					m.selected = 0
				}
			}
			return m, nil
		}
		if msg.String() == "q" {
			return m, tea.Quit
		}
		if m.detail {
			if msg.String() == "e" {
				m.openEditor(false)
				return m, nil
			}
			if msg.String() == "x" || msg.String() == "o" {
				m.askStatusChange(msg.String())
				return m, nil
			}
			lines := m.detailLines()
			page := max(1, m.height-11)
			last := max(0, len(lines)-page)
			switch msg.String() {
			case "esc", "left":
				m.detail, m.scroll = false, 0
			case "up", "k":
				m.scroll = max(0, m.scroll-1)
			case "down", "j":
				m.scroll = min(last, m.scroll+1)
			case "pgup":
				m.scroll = max(0, m.scroll-page)
			case "pgdown", " ":
				m.scroll = min(last, m.scroll+page)
			case "home", "g":
				m.scroll = 0
			case "end", "G":
				m.scroll = last
			}
			return m, nil
		}
		matches := m.filtered()
		switch msg.String() {
		case "up", "k":
			m.selected = max(0, m.selected-1)
		case "down", "j":
			m.selected = min(max(0, len(matches)-1), m.selected+1)
		case "pgup":
			m.selected = max(0, m.selected-max(1, m.height-11))
		case "pgdown":
			m.selected = min(max(0, len(matches)-1), m.selected+max(1, m.height-11))
		case "home", "g":
			m.selected = 0
		case "end", "G":
			m.selected = max(0, len(matches)-1)
		case "enter":
			if len(matches) > 0 {
				m.detail, m.scroll = true, 0
			}
		case "/":
			m.search = true
		case "esc":
			m.query = ""
			m.selected = 0
		case "r":
			m.reload("")
		case "n":
			m.openEditor(true)
		case "e":
			m.openEditor(false)
		case "x", "o":
			m.askStatusChange(msg.String())
		}
	}
	return m, nil
}

// Remove terminal control characters from content read from Markdown files.
func safe(text string) string {
	return strings.Map(func(r rune) rune {
		if r == '\n' || r == '\t' || !unicode.IsControl(r) {
			return r
		}
		return -1
	}, text)
}

func (m model) detailLines() []string {
	matches := m.filtered()
	if len(matches) == 0 || m.selected >= len(matches) {
		return nil
	}
	body := safe(m.items[matches[m.selected]].Body)
	if strings.TrimSpace(body) == "" {
		return []string{"(No description)"}
	}
	var lines []string
	for _, line := range strings.Split(strings.TrimRight(body, "\n"), "\n") {
		lines = append(lines, strings.Split(runewidth.Wrap(line, m.contentWidth()), "\n")...)
	}
	return lines
}

func (m model) contentWidth() int {
	if m.width < 50 || m.height < 14 || newTheme().plain {
		return max(1, min(m.width, 100))
	}
	return max(1, min(m.width, 100)-6) // border and horizontal padding
}

func (m model) View() string {
	if m.confirm != "" {
		return m.confirmView()
	}
	if m.editor != nil {
		return m.editorView()
	}
	t := newTheme()
	width := m.contentWidth()
	matches := m.filtered()
	if m.detail && len(matches) > 0 {
		todo := m.items[matches[m.selected]]
		lines := m.detailLines()
		page := max(1, m.height-11)
		start := min(m.scroll, max(0, len(lines)-page))
		end := min(start+page, len(lines))
		header := t.heading("DETAIL / "+safe(todo.Title), todo.ID+"  •  "+safe(todo.CreatedAt), width)
		meta := t.status(todo.Status) + "  " + t.muted.Render(safe(strings.Join(todo.Tags, ", ")))
		hint := fmt.Sprintf("%d-%d/%d  ↑↓ scroll · e edit · x/o status · Esc back · q quit", start+1, end, len(lines))
		if width < 60 {
			hint = "↑↓ scroll · e edit · Esc back · q quit"
		}
		content := header + "\n" + meta + "\n\n" + strings.Join(lines[start:end], "\n") +
			fmt.Sprintf("\n\n%s\n", t.hint(hint, width))
		if m.notice != "" {
			content += t.alert(m.notice, width) + "\n"
		}
		return t.box(content, m.width, m.height)
	}
	var out strings.Builder
	fmt.Fprintln(&out, t.heading("TODOS", fmt.Sprintf("%d shown / %d total  ·  %s", len(matches), len(m.items), safe(m.project)), width))
	if len(m.warnings) > 0 {
		fmt.Fprintln(&out, t.alert(fmt.Sprintf("Warning: %d unreadable todo(s): %s", len(m.warnings), m.warnings[0]), width))
	}
	fmt.Fprintln(&out, t.muted.Render(runewidth.Truncate(m.todosDir, width, "…")))
	out.WriteString("\n")
	if len(matches) == 0 {
		if len(m.items) == 0 {
			fmt.Fprintln(&out, t.muted.Render("No todos yet. Pi stores todo items in this directory."))
		} else {
			fmt.Fprintln(&out, t.muted.Render("No matching todos."))
		}
	} else {
		page := max(1, m.height-11)
		start := max(0, m.selected-page+1)
		end := min(start+page, len(matches))
		for i := start; i < end; i++ {
			todo := m.items[matches[i]]
			status := runewidth.Truncate(safe(todo.Status), max(1, min(16, width/3)), "…")
			tags := ""
			if width >= 60 {
				tags = runewidth.Truncate(safe(strings.Join(todo.Tags, ", ")), min(16, width/5), "…")
			}
			tagsWidth := 0
			if tags != "" {
				tagsWidth = 2 + runewidth.StringWidth(tags)
			}
			title := runewidth.Truncate(safe(todo.Title), max(1, width-16-runewidth.StringWidth(status)-tagsWidth), "…")
			line := todo.ID + "  [" + status + "]  " + title
			if tags != "" {
				line += "  " + tags
			}
			if i == m.selected {
				fmt.Fprintln(&out, t.row(line, true, width))
			} else {
				row := t.muted.Render("  "+todo.ID) + "  " + t.status(status) + "  " + title
				if tags != "" {
					row += "  " + t.muted.Render(tags)
				}
				fmt.Fprintln(&out, row)
			}
		}
	}
	search := "Search: " + safe(m.query)
	if m.search {
		search += "▏"
	}
	fmt.Fprintln(&out, "\n"+t.accent.Render(runewidth.Truncate(search, width, "…")))
	if m.notice != "" {
		fmt.Fprintln(&out, t.alert(m.notice, width))
	}
	hint := "↑↓ select · Enter view · / search · n new · e edit · x/o status · r refresh · q quit"
	if width < 40 {
		hint = "↑↓ select · Enter view · q quit"
	} else if width < 70 {
		hint = "↑↓ move · Enter view · / find · n new · e edit · q quit"
	}
	fmt.Fprintln(&out, t.hint(hint, width))
	return t.box(out.String(), m.width, m.height)
}