package filetree

import (
	"os"
	"path/filepath"
	"sort"
	"strings"
)

// Node represents a file or directory in the tree
type Node struct {
	Name     string
	Path     string
	IsDir    bool
	IsOpen   bool
	Level    int
	Parent   *Node
	Children []*Node
}

// Model represents the file tree state
type Model struct {
	Root     *Node
	Nodes    []*Node // Flattened visible nodes for navigation
	Cursor   int
	RootPath string
}

// New creates a new file tree model
func New(rootPath string) Model {
	absPath, err := filepath.Abs(rootPath)
	if err != nil {
		absPath = rootPath
	}

	root := &Node{
		Name:   filepath.Base(absPath),
		Path:   absPath,
		IsDir:  true,
		IsOpen: true,
		Level:  0,
	}

	m := Model{
		Root:     root,
		RootPath: absPath,
		Cursor:   0,
	}

	m.loadChildren(root)
	m.updateVisibleNodes()

	return m
}

// loadChildren loads the children of a directory node
func (m *Model) loadChildren(node *Node) {
	if !node.IsDir {
		return
	}

	entries, err := os.ReadDir(node.Path)
	if err != nil {
		return
	}

	// Sort: directories first, then alphabetically
	sort.Slice(entries, func(i, j int) bool {
		iDir := entries[i].IsDir()
		jDir := entries[j].IsDir()
		if iDir != jDir {
			return iDir
		}
		return strings.ToLower(entries[i].Name()) < strings.ToLower(entries[j].Name())
	})

	node.Children = make([]*Node, 0, len(entries))
	for _, entry := range entries {
		// Skip hidden files
		if strings.HasPrefix(entry.Name(), ".") {
			continue
		}

		child := &Node{
			Name:   entry.Name(),
			Path:   filepath.Join(node.Path, entry.Name()),
			IsDir:  entry.IsDir(),
			Level:  node.Level + 1,
			Parent: node,
		}
		node.Children = append(node.Children, child)
	}
}

// updateVisibleNodes updates the flattened list of visible nodes
func (m *Model) updateVisibleNodes() {
	m.Nodes = make([]*Node, 0)
	m.flattenNode(m.Root)
}

func (m *Model) flattenNode(node *Node) {
	m.Nodes = append(m.Nodes, node)
	if node.IsDir && node.IsOpen {
		for _, child := range node.Children {
			m.flattenNode(child)
		}
	}
}

// SelectedNode returns the currently selected node
func (m *Model) SelectedNode() *Node {
	if m.Cursor < 0 || m.Cursor >= len(m.Nodes) {
		return nil
	}
	return m.Nodes[m.Cursor]
}

// Toggle expands or collapses the selected directory
func (m *Model) Toggle() {
	node := m.SelectedNode()
	if node == nil || !node.IsDir {
		return
	}

	node.IsOpen = !node.IsOpen
	if node.IsOpen && len(node.Children) == 0 {
		m.loadChildren(node)
	}
	m.updateVisibleNodes()
}

// MoveUp moves the cursor up
func (m *Model) MoveUp() {
	if m.Cursor > 0 {
		m.Cursor--
	}
}

// MoveDown moves the cursor down
func (m *Model) MoveDown() {
	if m.Cursor < len(m.Nodes)-1 {
		m.Cursor++
	}
}

// Collapse collapses the current directory or moves to parent
func (m *Model) Collapse() {
	node := m.SelectedNode()
	if node == nil {
		return
	}

	if node.IsDir && node.IsOpen {
		node.IsOpen = false
		m.updateVisibleNodes()
	} else if node.Parent != nil {
		// Find parent in visible nodes
		for i, n := range m.Nodes {
			if n == node.Parent {
				m.Cursor = i
				break
			}
		}
	}
}

// Expand expands the current directory
func (m *Model) Expand() {
	node := m.SelectedNode()
	if node == nil || !node.IsDir {
		return
	}

	if !node.IsOpen {
		node.IsOpen = true
		if len(node.Children) == 0 {
			m.loadChildren(node)
		}
		m.updateVisibleNodes()
	}
}

// Ext returns the file extension of a node
func (n *Node) Ext() string {
	if n.IsDir {
		return ""
	}
	return strings.ToLower(filepath.Ext(n.Name))
}