// The MIT License (MIT)
//
// Copyright (C) 2026 Scott Duensing
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to
// deal in the Software without restriction, including without limitation the
// rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
// sell copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
// IN THE SOFTWARE.

#define DVX_WIDGET_IMPL
// widgetOps.c  -- Paint dispatcher and public widget operations
//
// This file contains two categories of functions:
//   1. The paint dispatcher (widgetPaintOne, widgetPaintOverlays, wgtPaint)
//      which walks the widget tree and calls per-type paint functions.
//   2. Public operations (wgtSetText, wgtSetEnabled, wgtSetVisible,
//      wgtFind, wgtDestroy, etc.) that form the widget system's public API.
//
// The paint dispatcher and the public operations are in the same file
// because they share the same invalidation infrastructure (wgtInvalidate
// and wgtInvalidatePaint).

#include "dvxWgtP.h"
#include "dvxPlat.h"
#include "stb_ds_wrap.h"
#include "../../../widgets/kpunch/box/box.h"

static bool sFullRepaint = false;

// Knuth multiplicative hash constant (2^32 / golden ratio).
#define KNUTH_HASH_MUL 2654435761u


// ============================================================
// Prototypes
// ============================================================

static void     debugContainerBorder(WidgetT *w, DisplayT *d, const BlitOpsT *ops);
static bool     pressableHitTest(const WidgetT *w, const WidgetT *root, int32_t x, int32_t y);
static WidgetT *wgtFindImpl(WidgetT *w, const char *name);
static bool     widgetDropFocusWithin(WidgetT *w);
static void     widgetNotifyChildChanged(WidgetT *w);


// Draws a 1px border in a neon color derived from the widget pointer.
// The Knuth multiplicative hash (KNUTH_HASH_MUL) distributes pointer values
// across the palette evenly so adjacent containers get different colors.
// This is only active when sDebugLayout is true (toggled via
// wgtSetDebugLayout), used during development to visualize container
// boundaries and diagnose layout issues.

static void debugContainerBorder(WidgetT *w, DisplayT *d, const BlitOpsT *ops) {
    static const uint8_t palette[][3] = {
        {255,   0, 255},  // magenta
        {  0, 255,   0},  // lime
        {255, 255,   0},  // yellow
        {  0, 255, 255},  // cyan
        {255, 128,   0},  // orange
        {128,   0, 255},  // purple
        {255,   0, 128},  // hot pink
        {  0, 128, 255},  // sky blue
        {128, 255,   0},  // chartreuse
        {255,  64,  64},  // salmon
        { 64, 255, 128},  // mint
        {255, 128, 255},  // orchid
    };

    uint32_t h     = (uint32_t)(uintptr_t)w * KNUTH_HASH_MUL;
    int32_t  idx   = (int32_t)((h >> 16) % DVX_ARRAY_LEN(palette));
    uint32_t color = packColor(d, palette[idx][0], palette[idx][1], palette[idx][2]);

    drawRectOutline(d, ops, w->x, w->y, w->w, w->h, color);
}


// Destroys a widget and its entire subtree. The order is:
//   1. Unlink from parent (so the parent doesn't reference freed memory)
//   2. Recursively destroy all children (depth-first)
//   3. Call the widget's own destroy callback (free buffers, etc.)
//   4. Clear any global state that references this widget
//   5. Clear the window's root pointer if this was the root
//   6. Free the widget memory
//
// This ordering ensures that per-widget destroy callbacks can still
// access the widget's data (step 3 comes after child cleanup but
// before the widget itself is freed).


// Shared hit test for pressable widgets: true when (x,y) falls within
// the widget bounds and the drag originated in the same window.
static bool pressableHitTest(const WidgetT *w, const WidgetT *root, int32_t x, int32_t y) {
    return w->window == root->window &&
           x >= w->x && x < w->x + w->w &&
           y >= w->y && y < w->y + w->h;
}


void wgtDestroy(WidgetT *w) {
    if (!w) {
        return;
    }

    // Notify parent chain of child destruction via onChildChanged vtable
    widgetNotifyChildChanged(w);

    if (w->parent) {
        widgetRemoveChild(w->parent, w);
    }

    widgetDestroyChildren(w);

    wclsDestroy(w);

    widgetClearReferences(w);

    // If this is the root, clear the window's reference
    if (w->window && w->window->widgetRoot == w) {
        w->window->widgetRoot = NULL;
    }

    free(w);
}


// Destroys all children of w, leaving w itself intact and childless.
// Each child goes through the full wgtDestroy path -- so parents get
// onChildChanged notifications and global references are cleared --
// unlike the internal bulk widgetDestroyChildren used during teardown.
// Use this when rebuilding a container's contents at runtime so the
// old subtrees are freed instead of leaked.
void wgtDestroyChildren(WidgetT *w) {
    if (!w) {
        return;
    }

    WidgetT *child = w->firstChild;

    while (child) {
        WidgetT *next = child->nextSibling;
        wgtDestroy(child);
        child = next;
    }
}


WidgetT *wgtFind(WidgetT *root, const char *name) {
    if (!root || !name) {
        return NULL;
    }

    return wgtFindImpl(root, name);
}


static WidgetT *wgtFindImpl(WidgetT *w, const char *name) {
    if (w->name[0] && strcmp(w->name, name) == 0) {
        return w;
    }

    for (WidgetT *c = w->firstChild; c; c = c->nextSibling) {
        WidgetT *found = wgtFindImpl(c, name);

        if (found) {
            return found;
        }
    }

    return NULL;
}


// Retrieves the AppContextT from any widget by walking up to the root.
// The root widget stores the context in its userData field (set during
// wgtInitWindow). This is the only way to get the AppContextT from
// deep inside the widget tree without passing it as a parameter
// through every function call. The walk is O(depth) but widget trees
// are shallow (typically 3-6 levels deep).

AppContextT *wgtGetContext(const WidgetT *w) {
    if (!w) {
        return NULL;
    }

    const WidgetT *root = w;

    while (root->parent) {
        root = root->parent;
    }

    return (AppContextT *)root->userData;
}


WidgetT *wgtGetFocused(void) {
    return sFocusedWidget;
}


// Polymorphic text getter  -- dispatches through the vtable to the
// appropriate getText implementation for the widget's type. Returns
// an empty string (not NULL) if the widget has no text or no getText
// handler, so callers don't need NULL checks.

const char *wgtGetText(const WidgetT *w) {
    if (!w) {
        return "";
    }

    return wclsGetText(w);
}


// Sets up a window for widget-based content. Creates a root VBox
// container and installs the four window callbacks (onPaint, onMouse,
// onKey, onResize) that bridge WM events into the widget system.
//
// The root widget's userData points to the AppContextT, which is
// the bridge back to the display, font, colors, and blitOps needed
// for painting. This avoids threading the context through every
// widget function  -- any widget can retrieve it via wgtGetContext().

WidgetT *wgtInitWindow(AppContextT *ctx, WindowT *win) {
    WidgetT *root = dvxBoxApi() ? dvxBoxApi()->vBox(NULL) : NULL;

    if (!root) {
        dvxLog("Widget: wgtInitWindow failed (%s)", dvxBoxApi() ? "vBox returned NULL" : "dvxBoxApi returned NULL");
        return NULL;
    }

    root->window   = win;
    root->userData = ctx;

    win->widgetRoot = root;
    win->onPaint    = widgetOnPaint;
    win->onMouse    = widgetOnMouse;
    win->onKey      = widgetOnKey;
    win->onKeyUp    = widgetOnKeyUp;
    win->onResize   = widgetOnResize;
    win->onBlur     = widgetOnBlur;
    win->onFocus    = widgetOnFocus;

    return root;
}


// Full invalidation: re-measures the widget tree, manages scrollbars,
// re-lays out, repaints, and dirties the window on screen.
//
// This is the "something structural changed" path  -- use when widget
// sizes may have changed (text changed, children added/removed,
// visibility toggled). If only visual state changed (cursor blink,
// selection highlight), use wgtInvalidatePaint() instead to skip
// the expensive measure/layout passes.
//
// The widgetOnPaint check ensures that custom paint handlers (used
// by some dialog implementations) aren't bypassed by the scrollbar
// management code.

void wgtInvalidate(WidgetT *w) {
    if (!w || !w->window) {
        return;
    }

    AppContextT *ctx = wgtGetContext(w);

    if (!ctx) {
        return;
    }

    // Manage scrollbars (measures, adds/removes scrollbars, relayouts)
    // Skip if window has a custom paint handler (e.g. dialog) that manages its own layout
    if (w->window->onPaint == widgetOnPaint) {
        widgetManageScrollbars(w->window, ctx);
    }

    // Full repaint — layout changed, all widgets need redrawing
    w->window->paintNeeded = PAINT_FULL;
    dvxInvalidateWindow(ctx, w->window);
}


// Lightweight repaint  -- skips measure/layout/scrollbar management.
// Use when only visual state changed (slider value, cursor blink,
// selection highlight, checkbox toggle) but widget sizes are stable.

void wgtInvalidatePaint(WidgetT *w) {
    if (!w || !w->window) {
        return;
    }

    // Mark only this widget as needing repaint
    w->paintDirty = true;

    // Propagate childDirty up through WCLASS_PAINTS_CHILDREN ancestors
    // so they know to recurse into children during partial repaints.
    WidgetT *root = w;

    while (root->parent) {
        root = root->parent;

        if (root->wclass && (root->wclass->flags & WCLASS_PAINTS_CHILDREN)) {
            root->childDirty = true;
        }
    }

    // Defer the actual paint — it will happen once in the main loop
    // before compositing, batching multiple invalidations into one
    // tree walk instead of one per call. Don't downgrade FULL to PARTIAL.
    if (w->window->paintNeeded < PAINT_PARTIAL) {
        w->window->paintNeeded = PAINT_PARTIAL;
    }
}


void wgtPaint(WidgetT *root, DisplayT *d, const BlitOpsT *ops, const BitmapFontT *font, const ColorSchemeT *colors, bool fullRepaint) {
    if (!root) {
        return;
    }

    sFullRepaint = fullRepaint;
    widgetPaintOne(root, d, ops, font, colors);
    sFullRepaint = false;
}


void wgtSetDebugLayout(AppContextT *ctx, bool enabled) {
    sDebugLayout = enabled;

    for (int32_t i = 0; i < ctx->stack.count; i++) {
        WindowT *win = ctx->stack.windows[i];

        if (win->widgetRoot) {
            wgtInvalidate(win->widgetRoot);
        }
    }
}


void wgtSetEnabled(WidgetT *w, bool enabled) {
    if (!w) {
        return;
    }

    w->enabled = enabled;

    // A disabled subtree must not keep keyboard focus.  Bail if the blur
    // callback destroyed widgets -- w may be gone.
    if (!enabled && !widgetDropFocusWithin(w)) {
        return;
    }

    wgtInvalidatePaint(w);
}


// Programmatic focus.  Disabled or hidden widgets (including children of a
// hidden container) cannot take focus; the transition itself is the shared
// widgetTransferFocus path.
void wgtSetFocused(WidgetT *w) {
    if (!w || !w->enabled || !widgetIsShown(w)) {
        return;
    }

    widgetTransferFocus(w);
}


void wgtSetName(WidgetT *w, const char *name) {
    if (!w || !name) {
        return;
    }

    strncpy(w->name, name, MAX_WIDGET_NAME - 1);
    w->name[MAX_WIDGET_NAME - 1] = '\0';
}


void wgtSetReadOnly(WidgetT *w, bool readOnly) {
    if (w) {
        w->readOnly = readOnly;
    }
}


// Polymorphic text setter. Dispatches to the type-specific setText
// via vtable, then does a full invalidation because changing text
// can change the widget's minimum size (triggering relayout).

void wgtSetText(WidgetT *w, const char *text) {
    if (!w) {
        return;
    }

    wclsSetText(w, text);

    wgtInvalidate(w);
}


void wgtSetTooltip(WidgetT *w, const char *text) {
    if (w) {
        // The on-screen tooltip may borrow the OLD string, whose owner may
        // free it before reassigning (e.g. a BASIC ToolTipText write);
        // hide it before the pointer is replaced.
        if (w->tooltip && w->tooltip != text && w->window && w->window->widgetRoot) {
            dvxInvalidateTooltip((AppContextT *)w->window->widgetRoot->userData, w->tooltip);
        }

        w->tooltip = text;
    }
}


void wgtSetVisible(WidgetT *w, bool visible) {
    if (!w) {
        return;
    }

    w->visible = visible;

    // A hidden subtree must not keep keyboard focus.  Bail if the blur
    // callback destroyed widgets -- w may be gone.
    if (!visible && !widgetDropFocusWithin(w)) {
        return;
    }

    // Notify parent chain of child visibility change via onChildChanged vtable
    widgetNotifyChildChanged(w);

    wgtInvalidate(w);
}


// Clears keyboard focus if the focused widget is w or one of its
// descendants (used when w is hidden or disabled).  Returns false if the
// blur callback destroyed widgets, in which case w may be dangling.
static bool widgetDropFocusWithin(WidgetT *w) {
    for (const WidgetT *p = sFocusedWidget; p; p = p->parent) {
        if (p == w) {
            return widgetTransferFocus(NULL);
        }
    }

    return true;
}


// Walks the ancestor chain and notifies the nearest ancestor that implements
// onChildChanged of a structural change to w (destroy, visibility toggle).
// Stops at the first ancestor that handles it.
static void widgetNotifyChildChanged(WidgetT *w) {
    if (!w->parent) {
        return;
    }

    for (WidgetT *p = w->parent; p; p = p->parent) {
        if (wclsHas(p, WGT_METHOD_ON_CHILD_CHANGED)) {
            wclsOnChildChanged(p, w);
            break;
        }
    }
}


// Recursive paint walker. For each visible widget:
//   1. Call the widget's paint function (if any) via vtable.
//   2. If the widget has WCLASS_PAINTS_CHILDREN, stop recursion  --
//      the widget's paint function already handled its children
//      (e.g. TabControl only paints the active tab's children).
//   3. Otherwise, recurse into children (default child painting).
//   4. Draw debug borders on top if debug layout is enabled.
//
// The paint order is parent-before-children, which means parent
// backgrounds are drawn first and children paint on top. This is
// the standard painter's algorithm for nested UI elements.

void widgetPaintOne(WidgetT *w, DisplayT *d, const BlitOpsT *ops, const BitmapFontT *font, const ColorSchemeT *colors) {
    if (!w->visible) {
        return;
    }

    // On partial repaints (fullRepaint=false), only paint dirty widgets.
    // The window's fullRepaint flag is stored in sFullRepaint for the
    // duration of the paint walk.
    bool dirty = w->paintDirty || sFullRepaint;

    // For WCLASS_PAINTS_CHILDREN widgets (TabControl, TreeView, ScrollPane,
    // Splitter): the generic child recursion below can't reach their
    // children, so these widgets must handle child painting themselves.
    // Only call their paint when something actually needs drawing.
    bool paintsChildren = w->wclass && (w->wclass->flags & WCLASS_PAINTS_CHILDREN);

    if (paintsChildren) {
        // On full repaint, ensure paintDirty is set so the paint function
        // redraws its chrome (the window background was cleared).
        if (sFullRepaint) {
            w->paintDirty = true;
        }

        // Skip entirely if nothing needs painting in this subtree
        if (!w->paintDirty && !w->childDirty) {
            return;
        }

        // When this widget itself is dirty (will clear its background),
        // all descendants must repaint on the fresh background.
        bool savedFull = sFullRepaint;

        if (w->paintDirty) {
            sFullRepaint = true;
        }

        wclsPaint(w, d, ops, font, colors);
        sFullRepaint   = savedFull;
        w->paintDirty  = false;
        w->childDirty  = false;

        if (sDebugLayout && dirty) {
            debugContainerBorder(w, d, ops);
        }

        return;
    }

    w->paintDirty = false;

    if (dirty) {
        wclsPaint(w, d, ops, font, colors);
    }

    // Always recurse into children — a clean parent may have dirty children
    for (WidgetT *c = w->firstChild; c; c = c->nextSibling) {
        widgetPaintOne(c, d, ops, font, colors);
    }

    // Debug: draw container borders on top of children
    if (sDebugLayout && dirty && w->firstChild) {
        debugContainerBorder(w, d, ops);
    }
}


// Paints popup overlays (open dropdowns/comboboxes) on top of
// the widget tree. Called AFTER the main paint pass so popups
// always render above all other widgets regardless of tree position.
//
// Only one popup can be open at a time (tracked by sOpenPopup).
// The tree-root ownership check prevents a popup from one window
// being painted into a different window's content buffer.

void widgetPaintOverlays(WidgetT *root, DisplayT *d, const BlitOpsT *ops, const BitmapFontT *font, const ColorSchemeT *colors) {
    if (!sOpenPopup) {
        return;
    }

    // Verify the popup belongs to this widget tree
    WidgetT *check = sOpenPopup;

    while (check->parent) {
        check = check->parent;
    }

    if (check != root) {
        return;
    }

    wclsPaintOverlay(sOpenPopup, d, ops, font, colors);
}


// Accelerator key activation: mimics keyboard press. The matching key-up
// event clears sKeyPressedBtn and fires onClick via wclsOnDragEnd.
void widgetPressableOnAccelActivate(WidgetT *w, WidgetT *root) {
    (void)root;
    w->pressed = true;
    sKeyPressedBtn = w;
    wgtInvalidatePaint(w);
}


// End of drag: clear pressed, fire onClick if released inside bounds.
void widgetPressableOnDragEnd(WidgetT *w, WidgetT *root, int32_t x, int32_t y) {
    w->pressed = false;

    if (pressableHitTest(w, root, x, y)) {
        if (w->onClick) {
            // The click handler may destroy this widget (a BASIC Click
            // handler unloading its own form); only repaint if it didn't.
            uint32_t gen = sWidgetGen;

            w->onClick(w);

            if (sWidgetGen != gen) {
                return;
            }
        }
    }

    wgtInvalidatePaint(w);
}


// Drag update: pressed tracks whether the cursor is still inside bounds,
// giving visual feedback as the user drags away or back onto the button.
void widgetPressableOnDragUpdate(WidgetT *w, WidgetT *root, int32_t x, int32_t y) {
    w->pressed = pressableHitTest(w, root, x, y);
    wgtInvalidatePaint(w);
}


// Keyboard activation (Space/Enter): sets pressed and stores the widget
// in sKeyPressedBtn so the key-up handler can fire onClick.
void widgetPressableOnKey(WidgetT *w, int32_t key, int32_t mod) {
    (void)mod;

    if (key == KEY_SPACE || key == KEY_ENTER) {
        w->pressed = true;
        sKeyPressedBtn = w;
        wgtInvalidatePaint(w);
    }
}


// Mouse press: take focus, mark pressed, register as the drag widget so
// the event dispatcher routes subsequent drag updates/end back here.
void widgetPressableOnMouse(WidgetT *w, WidgetT *root, int32_t vx, int32_t vy) {
    (void)root;
    (void)vx;
    (void)vy;
    sFocusedWidget = w;
    w->pressed = true;
    sDragWidget = w;
}


// Shared text getter for widgets whose DataT first field is
// `const char *text`. Returns empty string when nothing is set so
// callers never need a NULL check.
const char *widgetTextGet(const WidgetT *w) {
    if (!w || !w->data) {
        return "";
    }

    const char *t = *(const char **)w->data;

    return t ? t : "";
}


// Shared text setter for widgets whose DataT first field is
// `const char *text`. Replaces the owned strdup'd string and
// recomputes the accelerator from the '&' prefix.  The copy is made
// BEFORE the old string is freed so wgtSetText(w, wgtGetText(w)) is
// safe and a failed strdup keeps the old text instead of blanking it.
void widgetTextSet(WidgetT *w, const char *text) {
    if (!w || !w->data) {
        return;
    }

    const char **slot = (const char **)w->data;
    char        *copy = NULL;

    if (text) {
        copy = strdup(text);

        if (!copy) {
            dvxLog("Widget: failed to allocate text");
            return;
        }
    }

    free((void *)*slot);
    *slot       = copy;
    w->accelKey = accelParse(copy);
}