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//! The painter: one walk of the retained tree per frame, in dvui widgets.
//!
//! The tree carries no sizes and no widget state of its own. Everything here
//! reads props and answers events back into the tree, so the same tree could
//! be walked by a different painter — which is the whole point of the shape
//! `jolt-tui` already proves from the other side.

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

const tree_mod = @import("tree.zig");
const Tree = tree_mod.Tree;

/// Every widget here is keyed by the tree's `(generation, index)` identity, so
/// one `@src()` per tag is enough to keep dvui's ids apart.
fn opts(t: *Tree, id: u32) dvui.Options {
    var o: dvui.Options = .{ .id_extra = t.widgetId(id) };
    if (t.getNum(id, "width-request") > 0) {
        o.min_size_content = .{ .w = @floatCast(t.getNum(id, "width-request")), .h = 0 };
    }
    if (t.getNum(id, "margin") > 0) {
        const m: f32 = @floatCast(t.getNum(id, "margin"));
        o.margin = .{ .x = m, .y = m, .w = m, .h = m };
    }
    // `align` is the cross-axis pull a box gives a child: 0 start, 1 end.
    const a = t.getStr(id, "align");
    if (a.len != 0) {
        if (std.mem.eql(u8, a, "center")) {
            o.gravity_x = 0.5;
        } else if (std.mem.eql(u8, a, "end")) {
            o.gravity_x = 1.0;
        } else if (std.mem.eql(u8, a, "fill")) {
            o.expand = .horizontal;
        }
    }
    if (t.getBool(id, "fill-height")) o.expand = .both;
    return o;
}

fn direction(t: *Tree, id: u32) dvui.enums.Direction {
    const tag = (t.get(id) orelse return .vertical).tag;
    if (std.mem.eql(u8, tag, "hbox")) return .horizontal;
    if (std.mem.eql(u8, tag, "vbox")) return .vertical;
    const o = t.getStr(id, "orientation");
    if (std.mem.eql(u8, o, "horizontal")) return .horizontal;
    return .vertical;
}

/// The label a widget shows: `text` first, `label` second. Two names because
/// the tags disagree about which one reads better, not because they differ.
fn caption(t: *Tree, id: u32) []const u8 {
    const text = t.getStr(id, "text");
    if (text.len != 0) return text;
    return t.getStr(id, "label");
}

pub fn walk(t: *Tree, id: u32) void {
    const n = t.get(id) orelse return;
    const tag = n.tag;

    if (std.mem.eql(u8, tag, "window") or
        std.mem.eql(u8, tag, "box") or
        std.mem.eql(u8, tag, "hbox") or
        std.mem.eql(u8, tag, "vbox"))
    {
        var o = opts(t, id);
        if (o.expand == null) o.expand = .horizontal;
        var b = dvui.box(@src(), .{ .dir = direction(t, id) }, o);
        defer b.deinit();
        children(t, id, @floatCast(t.getNum(id, "spacing")));
        return;
    }

    if (std.mem.eql(u8, tag, "page")) {
        // A page is a column with a reading width, centred in whatever it got.
        var o = opts(t, id);
        o.expand = .both;
        var outer = dvui.box(@src(), .{ .dir = .horizontal }, o);
        defer outer.deinit();
        const max = t.getNum(id, "max-width");
        var inner = dvui.box(@src(), .{ .dir = .vertical }, .{
            .id_extra = t.widgetId(id),
            .expand = .vertical,
            .gravity_x = 0.5,
            .min_size_content = .{ .w = if (max > 0) @floatCast(max) else 0, .h = 0 },
            .max_size_content = if (max > 0) .width(@floatCast(max)) else null,
        });
        defer inner.deinit();
        children(t, id, @floatCast(t.getNum(id, "spacing")));
        return;
    }

    if (std.mem.eql(u8, tag, "card") or std.mem.eql(u8, tag, "frame")) {
        var o = opts(t, id);
        if (o.expand == null) o.expand = .horizontal;
        o.background = true;
        o.corners = dvui.CornerRect.all(6);
        o.border = dvui.Rect.all(1);
        o.padding = dvui.Rect.all(8);
        var b = dvui.box(@src(), .{ .dir = direction(t, id) }, o);
        defer b.deinit();
        children(t, id, @floatCast(t.getNum(id, "spacing")));
        return;
    }

    if (std.mem.eql(u8, tag, "scroll")) {
        var o = opts(t, id);
        o.expand = .both;
        var s = dvui.scrollArea(@src(), .{}, o);
        defer s.deinit();
        children(t, id, @floatCast(t.getNum(id, "spacing")));
        return;
    }

    if (std.mem.eql(u8, tag, "label") or
        std.mem.eql(u8, tag, "title") or
        std.mem.eql(u8, tag, "dim-label"))
    {
        var o = opts(t, id);
        if (std.mem.eql(u8, tag, "title")) {
            o.font = dvui.themeGet().font_title;
        } else if (std.mem.eql(u8, tag, "dim-label")) {
            o.color_text = .{ .color = dvui.themeGet().color(.window, .text).opacity(0.6) };
        }
        dvui.labelNoFmt(@src(), caption(t, id), .{ .align_x = o.gravity_x orelse 0 }, o);
        return;
    }

    if (std.mem.eql(u8, tag, "separator")) {
        var o = opts(t, id);
        if (o.expand == null) o.expand = .horizontal;
        o.min_size_content = .{ .w = 0, .h = 1 };
        _ = dvui.separator(@src(), o);
        return;
    }

    if (std.mem.eql(u8, tag, "spacer") or std.mem.eql(u8, tag, "gap")) {
        var o = opts(t, id);
        const size: f32 = @floatCast(t.getNum(id, "size"));
        o.min_size_content = .{ .w = size, .h = size };
        _ = dvui.spacer(@src(), o);
        return;
    }

    if (std.mem.eql(u8, tag, "button")) {
        var o = opts(t, id);
        // `sensitive` is absent by default, and absent means enabled — an
        // unset prop must not read as a dead button.
        const enabled = t.get(id).?.props.contains("sensitive") == false or t.getBool(id, "sensitive");
        if (!enabled) o.color_text = .{ .color = dvui.themeGet().color(.window, .text).opacity(0.4) };
        const kind = t.getStr(id, "kind");
        if (std.mem.eql(u8, kind, "primary")) {
            o.color_fill = .{ .color = dvui.themeGet().color(.highlight, .fill) };
        } else if (std.mem.eql(u8, kind, "destructive")) {
            o.color_fill = .{ .color = dvui.themeGet().color(.err, .fill) };
        }
        if (dvui.button(@src(), caption(t, id), .{}, o) and enabled) {
            t.emit(id, "click", "", 0);
        }
        return;
    }

    if (std.mem.eql(u8, tag, "checkbox") or std.mem.eql(u8, tag, "checkbutton")) {
        // dvui writes through the target, so the prop is the store: read it in,
        // let the widget edit it, write back what changed and say so.
        var checked = t.getBool(id, "value") or t.getBool(id, "active");
        const before = checked;
        _ = dvui.checkbox(@src(), &checked, caption(t, id), opts(t, id));
        if (checked != before) {
            t.setBool(id, "value", checked);
            t.setBool(id, "active", checked);
            t.emit(id, "toggled", "", if (checked) 1 else 0);
        }
        return;
    }

    if (std.mem.eql(u8, tag, "entry")) {
        entry(t, id);
        return;
    }

    if (std.mem.eql(u8, tag, "progress")) {
        var o = opts(t, id);
        if (o.expand == null) o.expand = .horizontal;
        o.min_size_content = .{ .w = 0, .h = 10 };
        dvui.progress(@src(), .{ .percent = @floatCast(t.getNum(id, "value")) }, o);
        return;
    }

    // An unknown tag is a container, not an error: a tree written against a
    // richer painter should still show its contents here rather than vanish.
    var b = dvui.box(@src(), .{ .dir = .vertical }, opts(t, id));
    defer b.deinit();
    children(t, id, @floatCast(t.getNum(id, "spacing")));
}

fn entry(t: *Tree, id: u32) void {
    const n = t.get(id) orelse return;
    if (n.entry == null) n.entry = .empty;
    if (!n.entry_seeded) {
        // The caller's `text` wins until the person typing changes it.
        const want = t.getStr(id, "text");
        n.entry.?.clearRetainingCapacity();
        n.entry.?.appendSlice(t.gpa, want) catch {};
        n.entry_seeded = true;
    }

    const placeholder = t.getStr(id, "placeholder");
    var o = opts(t, id);
    if (o.expand == null) o.expand = .horizontal;

    var te = dvui.textEntry(@src(), .{
        .text = .{ .array_list = .{ .backing = &n.entry.?, .allocator = t.gpa } },
        .placeholder = if (placeholder.len != 0) placeholder else null,
        .multiline = t.getBool(id, "multiline"),
    }, o);
    const changed = te.text_changed;
    const entered = te.enter_pressed;
    te.deinit();

    // Read the buffer back only after deinit: the widget updates the list there.
    const now = if (t.get(id)) |m| (if (m.entry) |buf| buf.items else "") else "";
    if (changed) {
        // Mirror into the prop so `zvui_node_get_str(node, "text")` answers what
        // is on screen, then emit — without disturbing `entry_seeded`, which
        // `setStr` would clear and so wipe the cursor position every keystroke.
        const owned = t.gpa.dupe(u8, now) catch return;
        defer t.gpa.free(owned);
        t.setStr(id, "text", owned);
        if (t.get(id)) |m| m.entry_seeded = true;
        t.emit(id, "change", owned, 0);
    }
    if (entered) t.emit(id, "activate", now, 0);
}

fn children(t: *Tree, id: u32, spacing: f32) void {
    const n = t.get(id) orelse return;
    // Copy the child list before walking it: painting emits events, and a
    // caller is free to restructure the tree between frames on the same thread.
    const kids = t.gpa.dupe(u32, n.children.items) catch return;
    defer t.gpa.free(kids);
    for (kids, 0..) |c, i| {
        if (spacing > 0 and i > 0) {
            _ = dvui.spacer(@src(), .{
                .id_extra = t.widgetId(c),
                .min_size_content = .{ .w = spacing, .h = spacing },
            });
        }
        walk(t, c);
    }
}