package ui

import (
	"fmt"
	"math"
	"regexp"
	"strconv"
	"strings"

	"github.com/charmbracelet/bubbles/list"
	"github.com/charmbracelet/bubbles/viewport"
	tea "github.com/charmbracelet/bubbletea"
	"github.com/charmbracelet/lipgloss"

	"github.com/oug-t/difi/internal/config"
	"github.com/oug-t/difi/internal/git"
	"github.com/oug-t/difi/internal/tree"
)

type Focus int

const (
	FocusTree Focus = iota
	FocusDiff
)

type Model struct {
	fileTree     list.Model
	treeDelegate TreeDelegate
	diffViewport viewport.Model

	selectedPath  string
	currentBranch string
	targetBranch  string
	repoName      string

	diffContent string
	diffLines   []string
	diffCursor  int

	inputBuffer string
	pendingZ    bool

	focus    Focus
	showHelp bool

	width, height int
}

func NewModel(cfg config.Config, targetBranch string) Model {
	InitStyles(cfg)

	files, _ := git.ListChangedFiles(targetBranch)
	items := tree.Build(files)

	delegate := TreeDelegate{Focused: true}
	l := list.New(items, delegate, 0, 0)

	l.SetShowTitle(false)
	l.SetShowHelp(false)
	l.SetShowStatusBar(false)
	l.SetFilteringEnabled(false)
	l.SetShowPagination(false)
	l.DisableQuitKeybindings()

	m := Model{
		fileTree:      l,
		treeDelegate:  delegate,
		diffViewport:  viewport.New(0, 0),
		focus:         FocusTree,
		currentBranch: git.GetCurrentBranch(),
		targetBranch:  targetBranch,
		repoName:      git.GetRepoName(),
		showHelp:      false,
		inputBuffer:   "",
		pendingZ:      false,
	}

	if len(items) > 0 {
		if first, ok := items[0].(tree.TreeItem); ok {
			m.selectedPath = first.FullPath
		}
	}
	return m
}

func (m Model) Init() tea.Cmd {
	if m.selectedPath != "" {
		return git.DiffCmd(m.targetBranch, m.selectedPath)
	}
	return nil
}

func (m *Model) getRepeatCount() int {
	if m.inputBuffer == "" {
		return 1
	}
	count, err := strconv.Atoi(m.inputBuffer)
	if err != nil {
		return 1
	}
	m.inputBuffer = ""
	return count
}

func (m Model) Update(msg tea.Msg) (tea.Model, tea.Cmd) {
	var cmd tea.Cmd
	var cmds []tea.Cmd

	keyHandled := false

	switch msg := msg.(type) {
	case tea.WindowSizeMsg:
		m.width = msg.Width
		m.height = msg.Height
		m.updateSizes()

	case tea.KeyMsg:
		if msg.String() == "q" || msg.String() == "ctrl+c" {
			return m, tea.Quit
		}

		if len(m.fileTree.Items()) == 0 {
			return m, nil
		}

		// Handle z-prefix commands (zz, zt, zb)
		if m.pendingZ {
			m.pendingZ = false
			if m.focus == FocusDiff {
				switch msg.String() {
				case "z", ".":
					m.centerDiffCursor()
				case "t":
					m.diffViewport.SetYOffset(m.diffCursor)
				case "b":
					offset := m.diffCursor - m.diffViewport.Height + 1
					if offset < 0 {
						offset = 0
					}
					m.diffViewport.SetYOffset(offset)
				}
			}
			return m, nil
		}

		if len(msg.String()) == 1 && strings.ContainsAny(msg.String(), "0123456789") {
			m.inputBuffer += msg.String()
			return m, nil
		}

		if msg.String() == "?" {
			m.showHelp = !m.showHelp
			m.updateSizes()
			return m, nil
		}

		switch msg.String() {
		case "tab":
			if m.focus == FocusTree {
				m.focus = FocusDiff
			} else {
				m.focus = FocusTree
			}
			m.updateTreeFocus()
			m.inputBuffer = ""

		case "l", "]", "ctrl+l", "right":
			m.focus = FocusDiff
			m.updateTreeFocus()
			m.inputBuffer = ""

		case "h", "[", "ctrl+h", "left":
			m.focus = FocusTree
			m.updateTreeFocus()
			m.inputBuffer = ""

		case "e", "enter":
			if m.selectedPath != "" {
				line := 0
				if m.focus == FocusDiff {
					line = git.CalculateFileLine(m.diffContent, m.diffCursor)
				} else {
					line = git.CalculateFileLine(m.diffContent, 0)
				}
				m.inputBuffer = ""
				return m, git.OpenEditorCmd(m.selectedPath, line)
			}

		// Viewport trigger
		case "z":
			if m.focus == FocusDiff {
				m.pendingZ = true
				return m, nil
			}

		// Cursor screen positioning (H, M, L)
		case "H":
			if m.focus == FocusDiff {
				m.diffCursor = m.diffViewport.YOffset
				if m.diffCursor >= len(m.diffLines) {
					m.diffCursor = len(m.diffLines) - 1
				}
			}

		case "M":
			if m.focus == FocusDiff {
				half := m.diffViewport.Height / 2
				m.diffCursor = m.diffViewport.YOffset + half
				if m.diffCursor >= len(m.diffLines) {
					m.diffCursor = len(m.diffLines) - 1
				}
			}

		case "L":
			if m.focus == FocusDiff {
				m.diffCursor = m.diffViewport.YOffset + m.diffViewport.Height - 1
				if m.diffCursor >= len(m.diffLines) {
					m.diffCursor = len(m.diffLines) - 1
				}
			}

		// Page navigation
		case "ctrl+d":
			if m.focus == FocusDiff {
				halfScreen := m.diffViewport.Height / 2
				m.diffCursor += halfScreen
				if m.diffCursor >= len(m.diffLines) {
					m.diffCursor = len(m.diffLines) - 1
				}
				m.centerDiffCursor()
			}
			m.inputBuffer = ""

		case "ctrl+u":
			if m.focus == FocusDiff {
				halfScreen := m.diffViewport.Height / 2
				m.diffCursor -= halfScreen
				if m.diffCursor < 0 {
					m.diffCursor = 0
				}
				m.centerDiffCursor()
			}
			m.inputBuffer = ""

		case "j", "down":
			keyHandled = true
			count := m.getRepeatCount()
			for i := 0; i < count; i++ {
				if m.focus == FocusDiff {
					if m.diffCursor < len(m.diffLines)-1 {
						m.diffCursor++
						// Scroll if hitting bottom edge
						if m.diffCursor >= m.diffViewport.YOffset+m.diffViewport.Height {
							m.diffViewport.LineDown(1)
						}
					}
				} else {
					m.fileTree.CursorDown()
				}
			}
			m.inputBuffer = ""

		case "k", "up":
			keyHandled = true
			count := m.getRepeatCount()
			for i := 0; i < count; i++ {
				if m.focus == FocusDiff {
					if m.diffCursor > 0 {
						m.diffCursor--
						// Scroll if hitting top edge
						if m.diffCursor < m.diffViewport.YOffset {
							m.diffViewport.LineUp(1)
						}
					}
				} else {
					m.fileTree.CursorUp()
				}
			}
			m.inputBuffer = ""

		default:
			m.inputBuffer = ""
		}
	}

	if len(m.fileTree.Items()) > 0 && m.focus == FocusTree {
		if !keyHandled {
			m.fileTree, cmd = m.fileTree.Update(msg)
			cmds = append(cmds, cmd)
		}

		if item, ok := m.fileTree.SelectedItem().(tree.TreeItem); ok && !item.IsDir {
			if item.FullPath != m.selectedPath {
				m.selectedPath = item.FullPath
				m.diffCursor = 0
				m.diffViewport.GotoTop()
				cmds = append(cmds, git.DiffCmd(m.targetBranch, m.selectedPath))
			}
		}
	}

	switch msg := msg.(type) {
	case git.DiffMsg:
		m.diffContent = msg.Content
		m.diffLines = strings.Split(msg.Content, "\n")
		m.diffViewport.SetContent(msg.Content)

	case git.EditorFinishedMsg:
		return m, git.DiffCmd(m.targetBranch, m.selectedPath)
	}

	return m, tea.Batch(cmds...)
}

func (m *Model) centerDiffCursor() {
	halfScreen := m.diffViewport.Height / 2
	targetOffset := m.diffCursor - halfScreen
	if targetOffset < 0 {
		targetOffset = 0
	}
	m.diffViewport.SetYOffset(targetOffset)
}

func (m *Model) updateSizes() {
	reservedHeight := 1
	if m.showHelp {
		reservedHeight += 6
	}

	contentHeight := m.height - reservedHeight
	if contentHeight < 1 {
		contentHeight = 1
	}

	treeWidth := int(float64(m.width) * 0.20)
	if treeWidth < 20 {
		treeWidth = 20
	}

	m.fileTree.SetSize(treeWidth, contentHeight)
	m.diffViewport.Width = m.width - treeWidth - 2
	m.diffViewport.Height = contentHeight
}

func (m *Model) updateTreeFocus() {
	m.treeDelegate.Focused = (m.focus == FocusTree)
	m.fileTree.SetDelegate(m.treeDelegate)
}

func (m Model) View() string {
	if m.width == 0 {
		return "Loading..."
	}

	if len(m.fileTree.Items()) == 0 {
		return m.viewEmptyState()
	}

	// Panes
	treeStyle := PaneStyle
	if m.focus == FocusTree {
		treeStyle = FocusedPaneStyle
	} else {
		treeStyle = PaneStyle
	}

	treeView := treeStyle.Copy().
		Width(m.fileTree.Width()).
		Height(m.fileTree.Height()).
		Render(m.fileTree.View())

	var renderedDiff strings.Builder
	start := m.diffViewport.YOffset
	end := start + m.diffViewport.Height
	if end > len(m.diffLines) {
		end = len(m.diffLines)
	}

	for i := start; i < end; i++ {
		line := m.diffLines[i]

		var numStr string
		mode := CurrentConfig.UI.LineNumbers

		if mode == "hidden" {
			numStr = ""
		} else {
			isCursor := (i == m.diffCursor)
			if isCursor && mode == "hybrid" {
				realLine := git.CalculateFileLine(m.diffContent, m.diffCursor)
				numStr = fmt.Sprintf("%d", realLine)
			} else if isCursor && mode == "relative" {
				numStr = "0"
			} else if mode == "absolute" {
				numStr = fmt.Sprintf("%d", i+1)
			} else {
				dist := int(math.Abs(float64(i - m.diffCursor)))
				numStr = fmt.Sprintf("%d", dist)
			}
		}

		lineNumRendered := ""
		if numStr != "" {
			lineNumRendered = LineNumberStyle.Render(numStr)
		}

		if m.focus == FocusDiff && i == m.diffCursor {
			cleanLine := stripAnsi(line)
			line = DiffSelectionStyle.Render("  " + cleanLine)
		} else {
			line = "  " + line
		}

		renderedDiff.WriteString(lineNumRendered + line + "\n")
	}

	diffView := DiffStyle.Copy().
		Width(m.diffViewport.Width).
		Height(m.diffViewport.Height).
		Render(renderedDiff.String())

	mainPanes := lipgloss.JoinHorizontal(lipgloss.Top, treeView, diffView)

	// Bottom area
	repoSection := StatusKeyStyle.Render(" " + m.repoName)
	divider := StatusDividerStyle.Render("│")

	statusText := fmt.Sprintf(" %s ↔ %s", m.currentBranch, m.targetBranch)
	if m.inputBuffer != "" {
		statusText += fmt.Sprintf(" [Cmd: %s]", m.inputBuffer)
	}
	branchSection := StatusBarStyle.Render(statusText)

	leftStatus := lipgloss.JoinHorizontal(lipgloss.Center, repoSection, divider, branchSection)
	rightStatus := StatusBarStyle.Render("? Help")

	statusBar := StatusBarStyle.Copy().
		Width(m.width).
		Render(lipgloss.JoinHorizontal(lipgloss.Top,
			leftStatus,
			lipgloss.PlaceHorizontal(m.width-lipgloss.Width(leftStatus)-lipgloss.Width(rightStatus), lipgloss.Right, rightStatus),
		))

	var finalView string
	if m.showHelp {
		col1 := lipgloss.JoinVertical(lipgloss.Left,
			HelpTextStyle.Render("↑/k   Move Up"),
			HelpTextStyle.Render("↓/j   Move Down"),
		)
		col2 := lipgloss.JoinVertical(lipgloss.Left,
			HelpTextStyle.Render("←/h   Left Panel"),
			HelpTextStyle.Render("→/l   Right Panel"),
		)
		col3 := lipgloss.JoinVertical(lipgloss.Left,
			HelpTextStyle.Render("C-d/u Page Dn/Up"),
			HelpTextStyle.Render("zz/zt Scroll View"),
		)
		col4 := lipgloss.JoinVertical(lipgloss.Left,
			HelpTextStyle.Render("H/M/L Move Cursor"),
			HelpTextStyle.Render("e     Edit File"),
		)

		helpDrawer := HelpDrawerStyle.Copy().
			Width(m.width).
			Render(lipgloss.JoinHorizontal(lipgloss.Top,
				col1,
				lipgloss.NewStyle().Width(4).Render(""),
				col2,
				lipgloss.NewStyle().Width(4).Render(""),
				col3,
				lipgloss.NewStyle().Width(4).Render(""),
				col4,
			))

		finalView = lipgloss.JoinVertical(lipgloss.Top, mainPanes, helpDrawer, statusBar)
	} else {
		finalView = lipgloss.JoinVertical(lipgloss.Top, mainPanes, statusBar)
	}

	return finalView
}

func (m Model) viewEmptyState() string {
	logo := EmptyLogoStyle.Render("difi")
	desc := EmptyDescStyle.Render("A calm, focused way to review Git diffs.")

	statusMsg := fmt.Sprintf("✓ No changes found against '%s'", m.targetBranch)
	status := EmptyStatusStyle.Render(statusMsg)

	usageHeader := EmptyHeaderStyle.Render("Usage Patterns")

	cmd1 := lipgloss.NewStyle().Foreground(ColorText).Render("difi")
	desc1 := EmptyCodeStyle.Render("Diff against main")

	cmd2 := lipgloss.NewStyle().Foreground(ColorText).Render("difi develop")
	desc2 := EmptyCodeStyle.Render("Diff against target branch")

	cmd3 := lipgloss.NewStyle().Foreground(ColorText).Render("difi HEAD~1")
	desc3 := EmptyCodeStyle.Render("Diff against previous commit")

	usageBlock := lipgloss.JoinVertical(lipgloss.Left,
		usageHeader,
		lipgloss.JoinHorizontal(lipgloss.Left, cmd1, desc1),
		lipgloss.JoinHorizontal(lipgloss.Left, cmd2, desc2),
		lipgloss.JoinHorizontal(lipgloss.Left, cmd3, desc3),
	)

	navHeader := EmptyHeaderStyle.Render("Navigation")

	key1 := lipgloss.NewStyle().Foreground(ColorText).Render("Tab")
	keyDesc1 := EmptyCodeStyle.Render("Switch panels")

	key2 := lipgloss.NewStyle().Foreground(ColorText).Render("j / k")
	keyDesc2 := EmptyCodeStyle.Render("Move cursor")

	key3 := lipgloss.NewStyle().Foreground(ColorText).Render("zz/zt")
	keyDesc3 := EmptyCodeStyle.Render("Center/Top")

	navBlock := lipgloss.JoinVertical(lipgloss.Left,
		navHeader,
		lipgloss.JoinHorizontal(lipgloss.Left, key1, keyDesc1),
		lipgloss.JoinHorizontal(lipgloss.Left, key2, keyDesc2),
		lipgloss.JoinHorizontal(lipgloss.Left, key3, keyDesc3),
	)

	guides := lipgloss.JoinHorizontal(lipgloss.Top,
		usageBlock,
		lipgloss.NewStyle().Width(8).Render(""),
		navBlock,
	)

	content := lipgloss.JoinVertical(lipgloss.Center,
		logo,
		desc,
		status,
		lipgloss.NewStyle().Height(1).Render(""),
		guides,
	)

	var verticalPad string
	if m.height > lipgloss.Height(content) {
		lines := (m.height - lipgloss.Height(content)) / 2
		verticalPad = strings.Repeat("\n", lines)
	}

	return lipgloss.JoinVertical(lipgloss.Top,
		verticalPad,
		lipgloss.PlaceHorizontal(m.width, lipgloss.Center, content),
	)
}

func stripAnsi(str string) string {
	re := regexp.MustCompile("[\u001B\u009B][[\\]()#;?]*(?:(?:(?:[a-zA-Z\\d]*(?:;[a-zA-Z\\d]*)*)?\u0007)|(?:(?:\\d{1,4}(?:;\\d{0,4})*)?[\\dA-PRZcf-ntqry=><~]))")
	return re.ReplaceAllString(str, "")
}