//! TextInput Widget - Editable text field
//!
//! A single-line text input with cursor, selection, and editing support.
//! Manages its own buffer that the caller provides.

const std = @import("std");
const Context = @import("../core/context.zig").Context;
const Command = @import("../core/command.zig");
const Layout = @import("../core/layout.zig");
const Style = @import("../core/style.zig");
const Input = @import("../core/input.zig");
const shortcuts = @import("../core/shortcuts.zig");

/// Text input state (caller-managed)
pub const TextInputState = struct {
    /// Text buffer
    buffer: []u8,
    /// Current text length
    len: usize = 0,
    /// Cursor position (byte index)
    cursor: usize = 0,
    /// Selection start (byte index), null if no selection
    selection_start: ?usize = null,
    /// Whether this input has focus
    focused: bool = false,

    /// Initialize with empty buffer
    pub fn init(buffer: []u8) TextInputState {
        return .{ .buffer = buffer };
    }

    /// Get the current text
    pub fn text(self: TextInputState) []const u8 {
        return self.buffer[0..self.len];
    }

    /// Set text programmatically
    pub fn setText(self: *TextInputState, new_text: []const u8) void {
        const copy_len = @min(new_text.len, self.buffer.len);
        @memcpy(self.buffer[0..copy_len], new_text[0..copy_len]);
        self.len = copy_len;
        self.cursor = copy_len;
        self.selection_start = null;
    }

    /// Clear the text
    pub fn clear(self: *TextInputState) void {
        self.len = 0;
        self.cursor = 0;
        self.selection_start = null;
    }

    /// Insert text at cursor
    pub fn insert(self: *TextInputState, new_text: []const u8) void {
        // Delete selection first if any
        self.deleteSelection();

        const available = self.buffer.len - self.len;
        const to_insert = @min(new_text.len, available);

        if (to_insert == 0) return;

        // Move text after cursor
        const after_cursor = self.len - self.cursor;
        if (after_cursor > 0) {
            std.mem.copyBackwards(
                u8,
                self.buffer[self.cursor + to_insert .. self.len + to_insert],
                self.buffer[self.cursor..self.len],
            );
        }

        // Insert new text
        @memcpy(self.buffer[self.cursor..][0..to_insert], new_text[0..to_insert]);
        self.len += to_insert;
        self.cursor += to_insert;
    }

    /// Delete character before cursor (backspace)
    pub fn deleteBack(self: *TextInputState) void {
        if (self.selection_start != null) {
            self.deleteSelection();
            return;
        }

        if (self.cursor == 0) return;

        // Move text after cursor back
        const after_cursor = self.len - self.cursor;
        if (after_cursor > 0) {
            std.mem.copyForwards(
                u8,
                self.buffer[self.cursor - 1 .. self.len - 1],
                self.buffer[self.cursor..self.len],
            );
        }

        self.cursor -= 1;
        self.len -= 1;
    }

    /// Delete character at cursor (delete key)
    pub fn deleteForward(self: *TextInputState) void {
        if (self.selection_start != null) {
            self.deleteSelection();
            return;
        }

        if (self.cursor >= self.len) return;

        // Move text after cursor back
        const after_cursor = self.len - self.cursor - 1;
        if (after_cursor > 0) {
            std.mem.copyForwards(
                u8,
                self.buffer[self.cursor .. self.len - 1],
                self.buffer[self.cursor + 1 .. self.len],
            );
        }

        self.len -= 1;
    }

    /// Delete selected text
    fn deleteSelection(self: *TextInputState) void {
        const start = self.selection_start orelse return;
        const sel_start = @min(start, self.cursor);
        const sel_end = @max(start, self.cursor);
        const sel_len = sel_end - sel_start;

        if (sel_len == 0) {
            self.selection_start = null;
            return;
        }

        // Move text after selection
        const after_sel = self.len - sel_end;
        if (after_sel > 0) {
            std.mem.copyForwards(
                u8,
                self.buffer[sel_start .. sel_start + after_sel],
                self.buffer[sel_end..self.len],
            );
        }

        self.len -= sel_len;
        self.cursor = sel_start;
        self.selection_start = null;
    }

    /// Move cursor left
    pub fn cursorLeft(self: *TextInputState, shift: bool) void {
        if (shift and self.selection_start == null) {
            self.selection_start = self.cursor;
        } else if (!shift) {
            self.selection_start = null;
        }

        if (self.cursor > 0) {
            self.cursor -= 1;
        }
    }

    /// Move cursor right
    pub fn cursorRight(self: *TextInputState, shift: bool) void {
        if (shift and self.selection_start == null) {
            self.selection_start = self.cursor;
        } else if (!shift) {
            self.selection_start = null;
        }

        if (self.cursor < self.len) {
            self.cursor += 1;
        }
    }

    /// Move cursor to start
    pub fn cursorHome(self: *TextInputState, shift: bool) void {
        if (shift and self.selection_start == null) {
            self.selection_start = self.cursor;
        } else if (!shift) {
            self.selection_start = null;
        }
        self.cursor = 0;
    }

    /// Move cursor to end
    pub fn cursorEnd(self: *TextInputState, shift: bool) void {
        if (shift and self.selection_start == null) {
            self.selection_start = self.cursor;
        } else if (!shift) {
            self.selection_start = null;
        }
        self.cursor = self.len;
    }

    /// Select all text
    pub fn selectAll(self: *TextInputState) void {
        self.selection_start = 0;
        self.cursor = self.len;
    }
};

/// Text input configuration
pub const TextInputConfig = struct {
    /// Placeholder text when empty
    placeholder: []const u8 = "",
    /// Read-only mode
    readonly: bool = false,
    /// Password mode (show dots instead of text)
    password: bool = false,
    /// Padding inside the input
    padding: u32 = 4,
    /// Override text color (for validation feedback). If null, uses theme default.
    text_color: ?Style.Color = null,
    /// Override border color (for validation feedback). If null, uses theme default.
    border_color: ?Style.Color = null,
    /// Corner radius (default 3 for fancy mode)
    corner_radius: u8 = 3,
};

/// Result of text input widget
pub const TextInputResult = struct {
    /// Text was changed this frame
    changed: bool,
    /// Enter was pressed
    submitted: bool,
    /// Widget was clicked (for focus management)
    clicked: bool,
};

/// Draw a text input and return interaction result
pub fn textInput(ctx: *Context, state: *TextInputState) TextInputResult {
    return textInputEx(ctx, state, .{});
}

/// Draw a text input with custom configuration
pub fn textInputEx(ctx: *Context, state: *TextInputState, config: TextInputConfig) TextInputResult {
    const bounds = ctx.layout.nextRect();
    return textInputRect(ctx, bounds, state, config);
}

/// Draw a text input in a specific rectangle
pub fn textInputRect(
    ctx: *Context,
    bounds: Layout.Rect,
    state: *TextInputState,
    config: TextInputConfig,
) TextInputResult {
    var result = TextInputResult{
        .changed = false,
        .submitted = false,
        .clicked = false,
    };

    if (bounds.isEmpty()) return result;

    // Generate unique ID for this widget based on buffer memory address
    const widget_id: u64 = @intFromPtr(state.buffer.ptr);

    // Register as focusable in the active focus group
    ctx.registerFocusable(widget_id);

    // Check mouse interaction
    const mouse = ctx.input.mousePos();
    const hovered = bounds.contains(mouse.x, mouse.y);
    const clicked = hovered and ctx.input.mousePressed(.left);

    if (clicked) {
        // Request focus - this also activates the group containing this widget
        ctx.requestFocus(widget_id);
        result.clicked = true;
    }

    // Check if this widget has focus (is focused widget in active group)
    const has_focus = ctx.hasFocus(widget_id);

    // Sync state.focused for backwards compatibility
    state.focused = has_focus;

    // Theme colors
    const theme = Style.Theme.dark;
    const bg_color = if (has_focus) theme.input_bg.lighten(5) else theme.input_bg;
    // Use override colors if provided, otherwise use theme defaults
    const border_color = config.border_color orelse (if (has_focus) theme.primary else theme.input_border);
    const text_color = config.text_color orelse theme.input_fg;
    const placeholder_color = theme.secondary;

    // Draw background and border based on render mode
    if (Style.isFancy() and config.corner_radius > 0) {
        // Fancy mode: rounded corners
        ctx.pushCommand(Command.roundedRect(bounds.x, bounds.y, bounds.w, bounds.h, bg_color, config.corner_radius));
        ctx.pushCommand(Command.roundedRectOutline(bounds.x, bounds.y, bounds.w, bounds.h, border_color, config.corner_radius));
        // Draw focus ring when focused
        if (has_focus) {
            ctx.pushCommand(Command.focusRing(bounds.x, bounds.y, bounds.w, bounds.h, config.corner_radius));
        }
    } else {
        // Simple mode: square corners
        ctx.pushCommand(Command.rect(bounds.x, bounds.y, bounds.w, bounds.h, bg_color));
        ctx.pushCommand(Command.rectOutline(bounds.x, bounds.y, bounds.w, bounds.h, border_color));
    }

    // Inner area
    const inner = bounds.shrink(config.padding);
    if (inner.isEmpty()) return result;

    // Handle keyboard input if focused
    if (has_focus and !config.readonly) {
        // Handle special keys (navigation, deletion)
        for (ctx.input.key_events[0..ctx.input.key_event_count]) |key_event| {
            if (key_event.pressed) {
                const shift = key_event.modifiers.shift;
                switch (key_event.key) {
                    .backspace => {
                        state.deleteBack();
                        result.changed = true;
                    },
                    .delete => {
                        state.deleteForward();
                        result.changed = true;
                    },
                    .left => state.cursorLeft(shift),
                    .right => state.cursorRight(shift),
                    .home => state.cursorHome(shift),
                    .end => state.cursorEnd(shift),
                    .enter => {
                        result.submitted = true;
                    },
                    else => {},
                }
            }
        }

        // Check standard shortcuts using centralized system
        if (shortcuts.isStandardActive(&ctx.input, .select_all)) {
            state.selectAll();
        }

        // Handle typed text
        const text_in = ctx.input.getTextInput();
        if (text_in.len > 0) {
            state.insert(text_in);
            result.changed = true;
        }
    }

    // Draw text or placeholder
    const display_text = if (state.len == 0)
        config.placeholder
    else
        state.text();

    const display_color = if (state.len == 0) placeholder_color else text_color;

    // Calculate text position (left-aligned, vertically centered)
    // Use 16 for 8x16 fonts (VGA standard, better readability)
    const char_height: u32 = 16;
    const text_y = inner.y + @as(i32, @intCast((inner.h -| char_height) / 2));

    if (config.password and state.len > 0) {
        // Draw dots for password
        var dots: [256]u8 = undefined;
        const dot_count = @min(state.len, dots.len);
        @memset(dots[0..dot_count], '*');
        ctx.pushCommand(Command.text(inner.x, text_y, dots[0..dot_count], display_color));
    } else {
        ctx.pushCommand(Command.text(inner.x, text_y, display_text, display_color));
    }

    // Draw cursor if focused
    // Hybrid behavior: blinks while active, solid after idle timeout
    if (has_focus and !config.readonly) {
        // Use ctx.measureTextToCursor for accurate cursor positioning with variable-width fonts
        const cursor_offset = ctx.measureTextToCursor(display_text, state.cursor);
        const cursor_x = inner.x + @as(i32, @intCast(cursor_offset));
        const cursor_color = theme.foreground;

        // Determine if cursor should be visible
        const cursor_visible = blk: {
            // If no timing available, always show cursor
            if (ctx.current_time_ms == 0) break :blk true;

            // Check idle time (time since last user input)
            const idle_time = ctx.current_time_ms -| ctx.last_input_time_ms;

            if (idle_time >= Context.CURSOR_IDLE_TIMEOUT_MS) {
                // Idle: cursor always visible (solid, no blink)
                break :blk true;
            } else {
                // Active: cursor blinks
                break :blk (ctx.current_time_ms / Context.CURSOR_BLINK_PERIOD_MS) % 2 == 0;
            }
        };

        if (cursor_visible) {
            ctx.pushCommand(Command.rect(
                cursor_x,
                inner.y,
                2,
                inner.h,
                cursor_color,
            ));
        }
    }

    // Draw selection if any
    if (state.selection_start) |sel_start| {
        const start = @min(sel_start, state.cursor);
        const end = @max(sel_start, state.cursor);
        // Use ctx.measureTextToCursor for accurate selection with variable-width fonts
        const start_offset = ctx.measureTextToCursor(display_text, start);
        const end_offset = ctx.measureTextToCursor(display_text, end);
        const sel_x = inner.x + @as(i32, @intCast(start_offset));
        const sel_w: u32 = end_offset - start_offset;

        if (sel_w > 0) {
            ctx.pushCommand(Command.rect(
                sel_x,
                inner.y,
                sel_w,
                inner.h,
                theme.selection_bg.blend(Style.Color.rgba(0, 0, 0, 128)),
            ));
        }
    }

    return result;
}

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

test "TextInputState insert" {
    var buf: [64]u8 = undefined;
    var state = TextInputState.init(&buf);

    state.insert("Hello");
    try std.testing.expectEqualStrings("Hello", state.text());
    try std.testing.expectEqual(@as(usize, 5), state.cursor);

    state.insert(" World");
    try std.testing.expectEqualStrings("Hello World", state.text());
}

test "TextInputState backspace" {
    var buf: [64]u8 = undefined;
    var state = TextInputState.init(&buf);

    state.insert("Hello");
    state.deleteBack();
    try std.testing.expectEqualStrings("Hell", state.text());

    state.deleteBack();
    state.deleteBack();
    try std.testing.expectEqualStrings("He", state.text());
}

test "TextInputState cursor movement" {
    var buf: [64]u8 = undefined;
    var state = TextInputState.init(&buf);

    state.insert("Hello");
    try std.testing.expectEqual(@as(usize, 5), state.cursor);

    state.cursorLeft(false);
    try std.testing.expectEqual(@as(usize, 4), state.cursor);

    state.cursorHome(false);
    try std.testing.expectEqual(@as(usize, 0), state.cursor);

    state.cursorEnd(false);
    try std.testing.expectEqual(@as(usize, 5), state.cursor);
}

test "TextInputState selection" {
    var buf: [64]u8 = undefined;
    var state = TextInputState.init(&buf);

    state.insert("Hello");
    state.selectAll();

    try std.testing.expectEqual(@as(?usize, 0), state.selection_start);
    try std.testing.expectEqual(@as(usize, 5), state.cursor);

    state.insert("X");
    try std.testing.expectEqualStrings("X", state.text());
}

test "textInput generates commands" {
    var ctx = try Context.init(std.testing.allocator, 800, 600);
    defer ctx.deinit();

    var buf: [64]u8 = undefined;
    var state = TextInputState.init(&buf);

    ctx.beginFrame();
    ctx.layout.row_height = 24;

    _ = textInput(&ctx, &state);

    // Should generate: rect (bg) + rect_outline (border) + text (placeholder)
    try std.testing.expect(ctx.commands.items.len >= 2);

    ctx.endFrame();
}