//! Viewport Demo - Shows scrollable content
//!
//! Run with: zig build viewport-demo

const std = @import("std");
const zcatui = @import("zcatui");

const Terminal = zcatui.Terminal;
const Rect = zcatui.Rect;
const Buffer = zcatui.Buffer;
const Style = zcatui.Style;
const Color = zcatui.Color;
const Block = zcatui.widgets.Block;
const Borders = zcatui.widgets.Borders;

// Sample content - pre-generated long text
const sample_content =
    \\  1 | === Welcome to the Viewport Demo ===
    \\  2 | This demonstrates scrollable content.
    \\  3 | Use j/k or arrows to scroll.
    \\  4 |
    \\  5 | Lorem ipsum dolor sit amet, line 5.
    \\  6 | Lorem ipsum dolor sit amet, line 6.
    \\  7 | Lorem ipsum dolor sit amet, line 7.
    \\  8 | Lorem ipsum dolor sit amet, line 8.
    \\  9 | Lorem ipsum dolor sit amet, line 9.
    \\ 10 | === Section 1 ===
    \\ 11 | Lorem ipsum dolor sit amet, line 11.
    \\ 12 | Lorem ipsum dolor sit amet, line 12.
    \\ 13 | Lorem ipsum dolor sit amet, line 13.
    \\ 14 | Lorem ipsum dolor sit amet, line 14.
    \\ 15 | --- subsection ---
    \\ 16 | Lorem ipsum dolor sit amet, line 16.
    \\ 17 | Lorem ipsum dolor sit amet, line 17.
    \\ 18 | Lorem ipsum dolor sit amet, line 18.
    \\ 19 | Lorem ipsum dolor sit amet, line 19.
    \\ 20 | === Section 2 ===
    \\ 21 | Lorem ipsum dolor sit amet, line 21.
    \\ 22 | Lorem ipsum dolor sit amet, line 22.
    \\ 23 | Lorem ipsum dolor sit amet, line 23.
    \\ 24 | Lorem ipsum dolor sit amet, line 24.
    \\ 25 | --- subsection ---
    \\ 26 | Lorem ipsum dolor sit amet, line 26.
    \\ 27 | Lorem ipsum dolor sit amet, line 27.
    \\ 28 | Lorem ipsum dolor sit amet, line 28.
    \\ 29 | Lorem ipsum dolor sit amet, line 29.
    \\ 30 | === Section 3 ===
    \\ 31 | Lorem ipsum dolor sit amet, line 31.
    \\ 32 | Lorem ipsum dolor sit amet, line 32.
    \\ 33 | Lorem ipsum dolor sit amet, line 33.
    \\ 34 | Lorem ipsum dolor sit amet, line 34.
    \\ 35 | --- subsection ---
    \\ 36 | Lorem ipsum dolor sit amet, line 36.
    \\ 37 | Lorem ipsum dolor sit amet, line 37.
    \\ 38 | Lorem ipsum dolor sit amet, line 38.
    \\ 39 | Lorem ipsum dolor sit amet, line 39.
    \\ 40 | === Section 4 ===
    \\ 41 | Lorem ipsum dolor sit amet, line 41.
    \\ 42 | Lorem ipsum dolor sit amet, line 42.
    \\ 43 | Lorem ipsum dolor sit amet, line 43.
    \\ 44 | Lorem ipsum dolor sit amet, line 44.
    \\ 45 | --- subsection ---
    \\ 46 | Lorem ipsum dolor sit amet, line 46.
    \\ 47 | Lorem ipsum dolor sit amet, line 47.
    \\ 48 | Lorem ipsum dolor sit amet, line 48.
    \\ 49 | Lorem ipsum dolor sit amet, line 49.
    \\ 50 | === End of content ===
;

/// State for the demo
const State = struct {
    offset_y: u16 = 0,
    content_height: u16 = 50,
    running: bool = true,
    view_height: u16 = 20,
};

pub fn main() !void {
    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
    defer _ = gpa.deinit();
    const allocator = gpa.allocator();

    var term = try Terminal.init(allocator);
    defer term.deinit();

    // Enable mouse for scroll wheel
    try term.enableMouseCapture();

    var state = State{};

    while (state.running) {
        state.view_height = term.area().height -| 4;
        try term.drawWithContext(&state, render);

        if (try term.pollEvent(100)) |event| {
            switch (event) {
                .key => |key| {
                    switch (key.code) {
                        .char => |c| {
                            if (c == 'q') state.running = false;
                            if (c == 'j') state.offset_y +|= 1;
                            if (c == 'k' and state.offset_y > 0) state.offset_y -= 1;
                            if (c == 'g') state.offset_y = 0;
                            if (c == 'G') state.offset_y = state.content_height -| state.view_height;
                        },
                        .up => if (state.offset_y > 0) {
                            state.offset_y -= 1;
                        },
                        .down => state.offset_y +|= 1,
                        .page_up => state.offset_y -|= state.view_height,
                        .page_down => state.offset_y +|= state.view_height,
                        .home => state.offset_y = 0,
                        .end => state.offset_y = state.content_height -| state.view_height,
                        .esc => state.running = false,
                        else => {},
                    }
                },
                .mouse => |mouse| {
                    switch (mouse.kind) {
                        .scroll_up => if (state.offset_y >= 3) {
                            state.offset_y -= 3;
                        },
                        .scroll_down => state.offset_y +|= 3,
                        else => {},
                    }
                },
                else => {},
            }
        }
    }
}

fn render(state: *State, area: Rect, buf: *Buffer) void {
    // Main border
    const block = Block.init()
        .title(" Viewport Demo ")
        .setBorders(Borders.all)
        .borderStyle((Style{}).fg(Color.cyan));
    block.render(area, buf);

    // Content area
    const content_area = Rect.init(1, 1, area.width -| 2, area.height -| 3);

    // Render visible content manually
    var lines = std.mem.splitScalar(u8, sample_content, '\n');
    var line_num: u16 = 0;
    var y: u16 = 0;
    while (lines.next()) |line| {
        if (line_num >= state.offset_y and y < content_area.height) {
            _ = buf.setString(content_area.x, content_area.y + y, line, Style{});
            y += 1;
        }
        line_num += 1;
    }

    // Scrollbar indicator
    const scroll_pct: u16 = if (state.content_height > state.view_height)
        @min(state.offset_y * 100 / (state.content_height -| state.view_height), 100)
    else
        0;

    // Footer with scroll info
    var footer_buf: [128]u8 = undefined;
    const footer = std.fmt.bufPrint(&footer_buf, "Line {d}/{d} ({d}%) | j/k up/down scroll, g/G top/bottom, PgUp/PgDn, q quit", .{
        state.offset_y + 1,
        state.content_height,
        scroll_pct,
    }) catch "...";

    _ = buf.setString(
        2,
        area.height -| 1,
        footer,
        (Style{}).fg(Color.rgb(100, 100, 100)),
    );
}