//! Directory Tree widget for file system navigation.
//!
//! A specialized tree view for browsing directories and files.
//! Features auto-expansion, filtering, icons, and file info display.
//!
//! ## Example
//!
//! ```zig
//! var tree = try DirectoryTree.init(allocator, "/home/user");
//! defer tree.deinit();
//!
//! // Navigate
//! tree.moveDown();
//! tree.toggleExpand();
//!
//! // Render
//! tree.render(area, buf);
//! ```

const std = @import("std");
const fs = std.fs;
const buffer_mod = @import("../buffer.zig");
const Buffer = buffer_mod.Buffer;
const Rect = buffer_mod.Rect;
const style_mod = @import("../style.zig");
const Style = style_mod.Style;
const Color = style_mod.Color;

/// File type for styling and icons
pub const FileKind = enum {
    directory,
    file,
    symlink,
    executable,
    hidden,
    special,

    pub fn fromEntry(entry: fs.Dir.Entry) FileKind {
        return switch (entry.kind) {
            .directory => .directory,
            .sym_link => .symlink,
            .file => .file,
            else => .special,
        };
    }
};

/// Icons for different file types
pub const FileIcons = struct {
    directory: []const u8 = "📁",
    directory_open: []const u8 = "📂",
    file: []const u8 = "📄",
    symlink: []const u8 = "🔗",
    executable: []const u8 = "⚙️",
    hidden: []const u8 = "👁",
    special: []const u8 = "❓",

    // File extension icons
    zig: []const u8 = "⚡",
    rust: []const u8 = "🦀",
    python: []const u8 = "🐍",
    javascript: []const u8 = "📜",
    markdown: []const u8 = "📝",
    image: []const u8 = "🖼",
    archive: []const u8 = "📦",
    config: []const u8 = "⚙️",
    git: []const u8 = "🔀",

    pub const default: FileIcons = .{};

    pub const ascii: FileIcons = .{
        .directory = "[D]",
        .directory_open = "[D]",
        .file = "   ",
        .symlink = "[@]",
        .executable = "[*]",
        .hidden = "[.]",
        .special = "[?]",
        .zig = "[Z]",
        .rust = "[R]",
        .python = "[P]",
        .javascript = "[J]",
        .markdown = "[M]",
        .image = "[I]",
        .archive = "[A]",
        .config = "[C]",
        .git = "[G]",
    };

    pub fn forFile(self: FileIcons, name: []const u8, kind: FileKind, expanded: bool) []const u8 {
        // Check for hidden files
        if (name.len > 0 and name[0] == '.') {
            // Git directory
            if (std.mem.eql(u8, name, ".git")) return self.git;
        }

        // By file kind
        switch (kind) {
            .directory => return if (expanded) self.directory_open else self.directory,
            .symlink => return self.symlink,
            .executable => return self.executable,
            .hidden => return self.hidden,
            .special => return self.special,
            .file => {
                // By extension
                if (getExtension(name)) |ext| {
                    if (std.mem.eql(u8, ext, "zig")) return self.zig;
                    if (std.mem.eql(u8, ext, "rs")) return self.rust;
                    if (std.mem.eql(u8, ext, "py")) return self.python;
                    if (std.mem.eql(u8, ext, "js") or std.mem.eql(u8, ext, "ts")) return self.javascript;
                    if (std.mem.eql(u8, ext, "md")) return self.markdown;
                    if (std.mem.eql(u8, ext, "png") or std.mem.eql(u8, ext, "jpg") or
                        std.mem.eql(u8, ext, "gif") or std.mem.eql(u8, ext, "svg"))
                        return self.image;
                    if (std.mem.eql(u8, ext, "zip") or std.mem.eql(u8, ext, "tar") or
                        std.mem.eql(u8, ext, "gz") or std.mem.eql(u8, ext, "7z"))
                        return self.archive;
                    if (std.mem.eql(u8, ext, "json") or std.mem.eql(u8, ext, "toml") or
                        std.mem.eql(u8, ext, "yaml") or std.mem.eql(u8, ext, "yml"))
                        return self.config;
                }
                return self.file;
            },
        }
    }
};

fn getExtension(name: []const u8) ?[]const u8 {
    const idx = std.mem.lastIndexOfScalar(u8, name, '.');
    if (idx) |i| {
        // Must have content after the dot, and dot can't be at start (hidden files)
        if (i > 0 and i + 1 < name.len) return name[i + 1 ..];
    }
    return null;
}

/// A node in the directory tree
pub const DirNode = struct {
    name: []const u8,
    path: []const u8,
    kind: FileKind,
    depth: u16,
    expanded: bool = false,
    loaded: bool = false,
    children_start: usize = 0,
    children_count: usize = 0,
    size: u64 = 0,
};

/// Theme for directory tree
pub const DirTreeTheme = struct {
    directory: Style = Style.default.fg(Color.blue).add_modifier(.{ .bold = true }),
    file: Style = Style.default,
    symlink: Style = Style.default.fg(Color.cyan),
    executable: Style = Style.default.fg(Color.green),
    hidden: Style = Style.default.fg(Color.indexed(245)),
    special: Style = Style.default.fg(Color.yellow),
    selected: Style = Style.default.bg(Color.indexed(236)),
    tree_guide: Style = Style.default.fg(Color.indexed(240)),
    size: Style = Style.default.fg(Color.indexed(245)),

    pub const default: DirTreeTheme = .{};
};

/// Tree drawing symbols
pub const TreeSymbols = struct {
    branch: []const u8 = "├── ",
    last_branch: []const u8 = "└── ",
    vertical: []const u8 = "│   ",
    space: []const u8 = "    ",
    collapsed: []const u8 = "▸ ",
    expanded: []const u8 = "▾ ",

    pub const default: TreeSymbols = .{};

    pub const ascii: TreeSymbols = .{
        .branch = "|-- ",
        .last_branch = "`-- ",
        .vertical = "|   ",
        .space = "    ",
        .collapsed = "+ ",
        .expanded = "- ",
    };
};

/// Directory tree widget
pub const DirectoryTree = struct {
    allocator: std.mem.Allocator,
    root_path: []const u8,
    nodes: std.ArrayListUnmanaged(DirNode),
    flat_view: std.ArrayListUnmanaged(usize), // Indices into nodes for visible items
    selected: usize = 0,
    scroll_offset: u16 = 0,
    theme: DirTreeTheme = DirTreeTheme.default,
    symbols: TreeSymbols = TreeSymbols.default,
    icons: FileIcons = FileIcons.default,
    show_hidden: bool = false,
    show_icons: bool = true,
    show_size: bool = false,
    filter: ?[]const u8 = null,

    /// Creates a new directory tree rooted at the given path
    pub fn init(allocator: std.mem.Allocator, root_path: []const u8) !DirectoryTree {
        var tree = DirectoryTree{
            .allocator = allocator,
            .root_path = try allocator.dupe(u8, root_path),
            .nodes = .{},
            .flat_view = .{},
        };

        // Add root node
        try tree.nodes.append(allocator, .{
            .name = try allocator.dupe(u8, std.fs.path.basename(root_path)),
            .path = tree.root_path,
            .kind = .directory,
            .depth = 0,
            .expanded = true,
            .loaded = false,
        });

        // Load root directory
        try tree.loadChildren(0);
        try tree.rebuildFlatView();

        return tree;
    }

    /// Frees all resources
    pub fn deinit(self: *DirectoryTree) void {
        for (self.nodes.items) |node| {
            if (node.name.ptr != node.path.ptr) {
                self.allocator.free(node.name);
            }
            if (node.depth > 0) {
                self.allocator.free(node.path);
            }
        }
        self.nodes.deinit(self.allocator);
        self.flat_view.deinit(self.allocator);
        self.allocator.free(self.root_path);
    }

    /// Loads children for a directory node
    fn loadChildren(self: *DirectoryTree, node_idx: usize) !void {
        var node = &self.nodes.items[node_idx];
        if (node.loaded or node.kind != .directory) return;

        var dir = fs.openDirAbsolute(node.path, .{ .iterate = true }) catch {
            node.loaded = true;
            return;
        };
        defer dir.close();

        const children_start = self.nodes.items.len;
        var children_count: usize = 0;

        var iter = dir.iterate();
        while (try iter.next()) |entry| {
            // Filter hidden files
            if (!self.show_hidden and entry.name.len > 0 and entry.name[0] == '.') {
                continue;
            }

            // Apply filter if set
            if (self.filter) |f| {
                if (std.mem.indexOf(u8, entry.name, f) == null) {
                    continue;
                }
            }

            const full_path = try fs.path.join(self.allocator, &.{ node.path, entry.name });
            const name = try self.allocator.dupe(u8, entry.name);

            try self.nodes.append(self.allocator, .{
                .name = name,
                .path = full_path,
                .kind = FileKind.fromEntry(entry),
                .depth = node.depth + 1,
            });
            children_count += 1;
        }

        // Sort children: directories first, then alphabetically
        const children = self.nodes.items[children_start..];
        std.mem.sort(DirNode, children, {}, struct {
            fn lessThan(_: void, a: DirNode, b: DirNode) bool {
                // Directories first
                if (a.kind == .directory and b.kind != .directory) return true;
                if (a.kind != .directory and b.kind == .directory) return false;
                // Then alphabetical (case-insensitive)
                return std.ascii.lessThanIgnoreCase(a.name, b.name);
            }
        }.lessThan);

        node.children_start = children_start;
        node.children_count = children_count;
        node.loaded = true;
    }

    /// Rebuilds the flat view based on expanded state
    fn rebuildFlatView(self: *DirectoryTree) !void {
        self.flat_view.clearRetainingCapacity();
        try self.addToFlatView(0);
    }

    fn addToFlatView(self: *DirectoryTree, node_idx: usize) !void {
        try self.flat_view.append(self.allocator, node_idx);

        const node = self.nodes.items[node_idx];
        if (node.expanded and node.loaded) {
            const children_end = node.children_start + node.children_count;
            for (node.children_start..children_end) |child_idx| {
                try self.addToFlatView(child_idx);
            }
        }
    }

    // Navigation methods
    pub fn moveUp(self: *DirectoryTree) void {
        if (self.selected > 0) {
            self.selected -= 1;
            self.ensureVisible();
        }
    }

    pub fn moveDown(self: *DirectoryTree) void {
        if (self.selected + 1 < self.flat_view.items.len) {
            self.selected += 1;
            self.ensureVisible();
        }
    }

    pub fn pageUp(self: *DirectoryTree, page_size: u16) void {
        if (self.selected > page_size) {
            self.selected -= page_size;
        } else {
            self.selected = 0;
        }
        self.ensureVisible();
    }

    pub fn pageDown(self: *DirectoryTree, page_size: u16) void {
        self.selected = @min(self.selected + page_size, self.flat_view.items.len -| 1);
        self.ensureVisible();
    }

    pub fn goToTop(self: *DirectoryTree) void {
        self.selected = 0;
        self.scroll_offset = 0;
    }

    pub fn goToBottom(self: *DirectoryTree) void {
        self.selected = self.flat_view.items.len -| 1;
        self.ensureVisible();
    }

    fn ensureVisible(self: *DirectoryTree) void {
        const sel = @as(u16, @intCast(self.selected));
        if (sel < self.scroll_offset) {
            self.scroll_offset = sel;
        }
        // Will be adjusted during render based on area height
    }

    /// Toggles expansion of the selected directory
    pub fn toggleExpand(self: *DirectoryTree) !void {
        if (self.flat_view.items.len == 0) return;

        const node_idx = self.flat_view.items[self.selected];
        var node = &self.nodes.items[node_idx];

        if (node.kind != .directory) return;

        if (!node.loaded) {
            try self.loadChildren(node_idx);
        }

        node.expanded = !node.expanded;
        try self.rebuildFlatView();

        // Adjust selected if it's now out of range
        if (self.selected >= self.flat_view.items.len) {
            self.selected = self.flat_view.items.len -| 1;
        }
    }

    /// Expands the selected directory
    pub fn expand(self: *DirectoryTree) !void {
        if (self.flat_view.items.len == 0) return;

        const node_idx = self.flat_view.items[self.selected];
        var node = &self.nodes.items[node_idx];

        if (node.kind != .directory or node.expanded) return;

        if (!node.loaded) {
            try self.loadChildren(node_idx);
        }

        node.expanded = true;
        try self.rebuildFlatView();
    }

    /// Collapses the selected directory
    pub fn collapse(self: *DirectoryTree) !void {
        if (self.flat_view.items.len == 0) return;

        const node_idx = self.flat_view.items[self.selected];
        var node = &self.nodes.items[node_idx];

        if (node.kind == .directory and node.expanded) {
            node.expanded = false;
            try self.rebuildFlatView();
        } else if (node.depth > 0) {
            // Go to parent
            self.goToParent();
        }
    }

    /// Navigates to the parent directory
    pub fn goToParent(self: *DirectoryTree) void {
        if (self.flat_view.items.len == 0) return;

        const node_idx = self.flat_view.items[self.selected];
        const node = self.nodes.items[node_idx];

        if (node.depth == 0) return;

        // Find parent in flat view
        for (self.flat_view.items, 0..) |idx, i| {
            const n = self.nodes.items[idx];
            if (n.depth == node.depth - 1 and
                n.children_start <= node_idx and
                node_idx < n.children_start + n.children_count)
            {
                self.selected = i;
                self.ensureVisible();
                break;
            }
        }
    }

    /// Returns the currently selected node
    pub fn getSelected(self: *const DirectoryTree) ?DirNode {
        if (self.flat_view.items.len == 0) return null;
        return self.nodes.items[self.flat_view.items[self.selected]];
    }

    /// Returns the path of the selected item
    pub fn getSelectedPath(self: *const DirectoryTree) ?[]const u8 {
        if (self.getSelected()) |node| {
            return node.path;
        }
        return null;
    }

    /// Toggles hidden file visibility
    pub fn toggleHidden(self: *DirectoryTree) !void {
        self.show_hidden = !self.show_hidden;
        // Reload all expanded directories
        for (self.nodes.items) |*node| {
            if (node.expanded) {
                node.loaded = false;
            }
        }
        // Clear and reload
        self.nodes.shrinkRetainingCapacity(1);
        self.nodes.items[0].loaded = false;
        self.nodes.items[0].children_count = 0;
        try self.loadChildren(0);
        try self.rebuildFlatView();
        self.selected = @min(self.selected, self.flat_view.items.len -| 1);
    }

    // Builder methods
    pub fn setTheme(self: DirectoryTree, t: DirTreeTheme) DirectoryTree {
        var tree = self;
        tree.theme = t;
        return tree;
    }

    pub fn setSymbols(self: DirectoryTree, s: TreeSymbols) DirectoryTree {
        var tree = self;
        tree.symbols = s;
        return tree;
    }

    pub fn setIcons(self: DirectoryTree, i: FileIcons) DirectoryTree {
        var tree = self;
        tree.icons = i;
        return tree;
    }

    pub fn setShowHidden(self: DirectoryTree, show: bool) DirectoryTree {
        var tree = self;
        tree.show_hidden = show;
        return tree;
    }

    pub fn setShowIcons(self: DirectoryTree, show: bool) DirectoryTree {
        var tree = self;
        tree.show_icons = show;
        return tree;
    }

    pub fn setShowSize(self: DirectoryTree, show: bool) DirectoryTree {
        var tree = self;
        tree.show_size = show;
        return tree;
    }

    /// Renders the directory tree
    pub fn render(self: *DirectoryTree, area: Rect, buf: *Buffer) void {
        if (area.isEmpty() or self.flat_view.items.len == 0) return;

        // Adjust scroll to keep selected visible
        const sel = @as(u16, @intCast(self.selected));
        if (sel >= self.scroll_offset + area.height) {
            self.scroll_offset = sel - area.height + 1;
        }
        if (sel < self.scroll_offset) {
            self.scroll_offset = sel;
        }

        var y: u16 = 0;
        var visible_idx: u16 = 0;

        for (self.flat_view.items) |node_idx| {
            if (visible_idx < self.scroll_offset) {
                visible_idx += 1;
                continue;
            }

            if (y >= area.height) break;

            const node = self.nodes.items[node_idx];
            const is_selected = visible_idx == @as(u16, @intCast(self.selected));

            self.renderNode(node, is_selected, area.x, area.y + y, area.width, buf);

            y += 1;
            visible_idx += 1;
        }
    }

    fn renderNode(
        self: *const DirectoryTree,
        node: DirNode,
        is_selected: bool,
        x: u16,
        y: u16,
        width: u16,
        buf: *Buffer,
    ) void {
        var pos = x;

        // Selection highlight (fill entire line)
        if (is_selected) {
            var fill_x = x;
            while (fill_x < x + width) : (fill_x += 1) {
                if (buf.getPtr(fill_x, y)) |cell| {
                    cell.bg = self.theme.selected.background orelse Color.indexed(236);
                }
            }
        }

        // Indentation with tree guides
        const indent = node.depth * 4;
        pos += @intCast(indent);

        // Expand/collapse indicator for directories
        if (node.kind == .directory) {
            const indicator = if (node.expanded) self.symbols.expanded else self.symbols.collapsed;
            pos = buf.setString(pos, y, indicator, self.theme.tree_guide);
        }

        // Icon
        if (self.show_icons) {
            const icon = self.icons.forFile(node.name, node.kind, node.expanded);
            pos = buf.setString(pos, y, icon, self.getStyleForKind(node.kind));
            pos = buf.setString(pos, y, " ", Style.default);
        }

        // Name
        const name_style = if (is_selected)
            self.getStyleForKind(node.kind).bg(self.theme.selected.background orelse Color.indexed(236))
        else
            self.getStyleForKind(node.kind);

        _ = buf.setString(pos, y, node.name, name_style);
    }

    fn getStyleForKind(self: *const DirectoryTree, kind: FileKind) Style {
        return switch (kind) {
            .directory => self.theme.directory,
            .file => self.theme.file,
            .symlink => self.theme.symlink,
            .executable => self.theme.executable,
            .hidden => self.theme.hidden,
            .special => self.theme.special,
        };
    }
};

// ============================================================================
// Tests
// ============================================================================

test "FileIcons forFile" {
    const icons = FileIcons.default;

    try std.testing.expectEqualStrings("📁", icons.forFile("src", .directory, false));
    try std.testing.expectEqualStrings("📂", icons.forFile("src", .directory, true));
    try std.testing.expectEqualStrings("⚡", icons.forFile("main.zig", .file, false));
    try std.testing.expectEqualStrings("🐍", icons.forFile("app.py", .file, false));
    try std.testing.expectEqualStrings("📄", icons.forFile("readme.txt", .file, false));
}

test "getExtension" {
    try std.testing.expectEqualStrings("zig", getExtension("main.zig").?);
    try std.testing.expectEqualStrings("rs", getExtension("lib.rs").?);
    try std.testing.expectEqualStrings("gz", getExtension("archive.tar.gz").?);
    try std.testing.expect(getExtension("noextension") == null);
    try std.testing.expect(getExtension(".hidden") == null);
}

test "FileKind fromEntry" {
    // Basic type detection (can't easily test without real fs entries)
    _ = FileKind.directory;
    _ = FileKind.file;
    _ = FileKind.symlink;
}