// widgetSplitter.c  -- Splitter (draggable divider between two panes)
//
// A container that divides its area between exactly two child widgets
// with a draggable divider bar between them. The divider position
// (dividerPos) is stored as a pixel offset from the leading edge
// (left for vertical, top for horizontal).
//
// Architecture: the splitter is a special container (has its own
// layout function) that manually positions its two children and the
// divider bar. It does NOT use the generic box layout. Children are
// clipped to their respective panes during painting to prevent
// overflow into the other pane.
//
// The divider bar (SPLITTER_BAR_W = 5px) is drawn as a raised bevel
// with a "gripper" pattern -- small embossed 2x2 bumps arranged
// in a line centered on the bar. This provides visual feedback that
// the bar is draggable, following the Win3.1/Motif convention.
//
// Drag state: divider dragging stores the clicked splitter widget
// and the mouse offset within the bar in globals (sDragSplitter,
// sDragSplitStart). The event loop handles mouse-move during drag
// by computing the new divider position from mouse coordinates and
// calling widgetSplitterClampPos to enforce minimum pane sizes.
//
// Minimum pane sizes come from children's calcMinW/H, with a floor
// of SPLITTER_MIN_PANE (20px) to prevent panes from collapsing to
// nothing. The clamp also ensures the divider can't be dragged past
// where the second pane would violate its minimum.

#include "widgetInternal.h"


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

static WidgetT *spFirstChild(WidgetT *w);
static WidgetT *spSecondChild(WidgetT *w);


// ============================================================
// spFirstChild  -- get first visible child
// ============================================================

// These helpers skip invisible children so the splitter works
// correctly even if one pane is hidden. The splitter only cares
// about the first two visible children; any additional children
// are ignored (though this shouldn't happen in practice).
static WidgetT *spFirstChild(WidgetT *w) {
    for (WidgetT *c = w->firstChild; c; c = c->nextSibling) {
        if (c->visible) {
            return c;
        }
    }

    return NULL;
}


// ============================================================
// spSecondChild  -- get second visible child
// ============================================================

static WidgetT *spSecondChild(WidgetT *w) {
    int32_t n = 0;

    for (WidgetT *c = w->firstChild; c; c = c->nextSibling) {
        if (c->visible) {
            n++;

            if (n == 2) {
                return c;
            }
        }
    }

    return NULL;
}


// ============================================================
// widgetSplitterClampPos  -- clamp divider to child minimums
// ============================================================

void widgetSplitterClampPos(WidgetT *w, int32_t *pos) {
    WidgetT *c1   = spFirstChild(w);
    WidgetT *c2   = spSecondChild(w);
    bool     vert = w->as.splitter.vertical;
    int32_t  totalSize = vert ? w->w : w->h;

    int32_t minFirst  = c1 ? (vert ? c1->calcMinW : c1->calcMinH) : SPLITTER_MIN_PANE;
    int32_t minSecond = c2 ? (vert ? c2->calcMinW : c2->calcMinH) : SPLITTER_MIN_PANE;

    if (minFirst < SPLITTER_MIN_PANE) {
        minFirst = SPLITTER_MIN_PANE;
    }

    if (minSecond < SPLITTER_MIN_PANE) {
        minSecond = SPLITTER_MIN_PANE;
    }

    int32_t maxPos = totalSize - SPLITTER_BAR_W - minSecond;

    if (maxPos < minFirst) {
        maxPos = minFirst;
    }

    *pos = clampInt(*pos, minFirst, maxPos);
}


// ============================================================
// widgetSplitterCalcMinSize
// ============================================================

void widgetSplitterCalcMinSize(WidgetT *w, const BitmapFontT *font) {
    // Recursively measure children
    for (WidgetT *c = w->firstChild; c; c = c->nextSibling) {
        widgetCalcMinSizeTree(c, font);
    }

    WidgetT *c1 = spFirstChild(w);
    WidgetT *c2 = spSecondChild(w);
    int32_t  m1w = c1 ? c1->calcMinW : 0;
    int32_t  m1h = c1 ? c1->calcMinH : 0;
    int32_t  m2w = c2 ? c2->calcMinW : 0;
    int32_t  m2h = c2 ? c2->calcMinH : 0;

    if (w->as.splitter.vertical) {
        w->calcMinW = m1w + m2w + SPLITTER_BAR_W;
        w->calcMinH = DVX_MAX(m1h, m2h);
    } else {
        w->calcMinW = DVX_MAX(m1w, m2w);
        w->calcMinH = m1h + m2h + SPLITTER_BAR_W;
    }
}


// ============================================================
// widgetSplitterLayout
// ============================================================

// Layout assigns each child its full pane area, then recurses into
// child layouts. The first child gets [0, dividerPos) and the second
// gets [dividerPos + SPLITTER_BAR_W, end). The divider position is
// clamped before use to respect minimum pane sizes, even if the
// user hasn't dragged yet (dividerPos=0 from construction gets
// clamped to minFirst).
void widgetSplitterLayout(WidgetT *w, const BitmapFontT *font) {
    WidgetT *c1 = spFirstChild(w);
    WidgetT *c2 = spSecondChild(w);
    int32_t  pos = w->as.splitter.dividerPos;

    widgetSplitterClampPos(w, &pos);
    w->as.splitter.dividerPos = pos;

    if (w->as.splitter.vertical) {
        // Left pane
        if (c1) {
            c1->x = w->x;
            c1->y = w->y;
            c1->w = pos;
            c1->h = w->h;
            widgetLayoutChildren(c1, font);
        }

        // Right pane
        if (c2) {
            c2->x = w->x + pos + SPLITTER_BAR_W;
            c2->y = w->y;
            c2->w = w->w - pos - SPLITTER_BAR_W;
            c2->h = w->h;

            if (c2->w < 0) {
                c2->w = 0;
            }

            widgetLayoutChildren(c2, font);
        }
    } else {
        // Top pane
        if (c1) {
            c1->x = w->x;
            c1->y = w->y;
            c1->w = w->w;
            c1->h = pos;
            widgetLayoutChildren(c1, font);
        }

        // Bottom pane
        if (c2) {
            c2->x = w->x;
            c2->y = w->y + pos + SPLITTER_BAR_W;
            c2->w = w->w;
            c2->h = w->h - pos - SPLITTER_BAR_W;

            if (c2->h < 0) {
                c2->h = 0;
            }

            widgetLayoutChildren(c2, font);
        }
    }
}


// ============================================================
// widgetSplitterOnMouse
// ============================================================

// Mouse handling first checks if the click is on the divider bar.
// If so, it starts a drag. If not, it recursively hit-tests into
// children and forwards the event. This manual hit-test forwarding
// is needed because the splitter has WCLASS_NO_HIT_RECURSE (the
// generic hit-test would find the splitter but not recurse into its
// clipped children).
void widgetSplitterOnMouse(WidgetT *hit, WidgetT *root, int32_t vx, int32_t vy) {
    int32_t pos = hit->as.splitter.dividerPos;

    // Check if click is on the divider bar
    bool onDivider;

    if (hit->as.splitter.vertical) {
        int32_t barX = hit->x + pos;
        onDivider = (vx >= barX && vx < barX + SPLITTER_BAR_W);
    } else {
        int32_t barY = hit->y + pos;
        onDivider = (vy >= barY && vy < barY + SPLITTER_BAR_W);
    }

    if (onDivider) {
        // Start dragging
        sDragSplitter = hit;

        if (hit->as.splitter.vertical) {
            sDragSplitStart = vx - hit->x - pos;
        } else {
            sDragSplitStart = vy - hit->y - pos;
        }

        return;
    }

    // Forward click to child widgets
    WidgetT *child = NULL;

    for (WidgetT *c = hit->firstChild; c; c = c->nextSibling) {
        WidgetT *ch = widgetHitTest(c, vx, vy);

        if (ch) {
            child = ch;
        }
    }

    if (child && child->enabled && child->wclass && child->wclass->onMouse) {
        if (sFocusedWidget && sFocusedWidget != child) {
            sFocusedWidget->focused = false;
        }

        child->wclass->onMouse(child, root, vx, vy);

        if (child->focused) {
            sFocusedWidget = child;
        }
    }

    wgtInvalidatePaint(hit);
}


// ============================================================
// widgetSplitterPaint
// ============================================================

// Paint clips each child to its pane area, preventing overflow across
// the divider. The clip rect is saved/restored around each child's
// paint. The divider bar is painted last (on top) so it's always
// visible even if a child overflows.
//
// The gripper bumps use the classic embossed-dot technique: a
// highlight pixel at (x,y) and a shadow pixel at (x+1,y+1) create
// a tiny raised bump. 11 bumps spaced 3px apart center vertically
// (or horizontally) on the bar. This is purely decorative but
// provides the expected visual affordance for "draggable".
void widgetSplitterPaint(WidgetT *w, DisplayT *d, const BlitOpsT *ops, const BitmapFontT *font, const ColorSchemeT *colors) {
    int32_t pos = w->as.splitter.dividerPos;

    // Paint first child with clip rect
    WidgetT *c1 = spFirstChild(w);
    WidgetT *c2 = spSecondChild(w);

    int32_t oldClipX = d->clipX;
    int32_t oldClipY = d->clipY;
    int32_t oldClipW = d->clipW;
    int32_t oldClipH = d->clipH;

    if (c1) {
        if (w->as.splitter.vertical) {
            setClipRect(d, w->x, w->y, pos, w->h);
        } else {
            setClipRect(d, w->x, w->y, w->w, pos);
        }

        widgetPaintOne(c1, d, ops, font, colors);
        setClipRect(d, oldClipX, oldClipY, oldClipW, oldClipH);
    }

    if (c2) {
        if (w->as.splitter.vertical) {
            setClipRect(d, w->x + pos + SPLITTER_BAR_W, w->y, w->w - pos - SPLITTER_BAR_W, w->h);
        } else {
            setClipRect(d, w->x, w->y + pos + SPLITTER_BAR_W, w->w, w->h - pos - SPLITTER_BAR_W);
        }

        widgetPaintOne(c2, d, ops, font, colors);
        setClipRect(d, oldClipX, oldClipY, oldClipW, oldClipH);
    }

    // Draw divider bar  -- raised bevel
    BevelStyleT bevel = BEVEL_RAISED(colors, 1);

    if (w->as.splitter.vertical) {
        int32_t barX = w->x + pos;
        drawBevel(d, ops, barX, w->y, SPLITTER_BAR_W, w->h, &bevel);

        // Gripper  -- row of embossed 2x2 bumps centered vertically
        int32_t gx = barX + 1;
        int32_t midY = w->y + w->h / 2;
        int32_t count = 5;

        for (int32_t i = -count; i <= count; i++) {
            int32_t dy = midY + i * 3;
            drawHLine(d, ops, gx, dy, 2, colors->windowHighlight);
            drawHLine(d, ops, gx + 1, dy + 1, 2, colors->windowShadow);
        }
    } else {
        int32_t barY = w->y + pos;
        drawBevel(d, ops, w->x, barY, w->w, SPLITTER_BAR_W, &bevel);

        // Gripper  -- row of embossed 2x2 bumps centered horizontally
        int32_t gy = barY + 1;
        int32_t midX = w->x + w->w / 2;
        int32_t count = 5;

        for (int32_t i = -count; i <= count; i++) {
            int32_t dx = midX + i * 3;
            drawHLine(d, ops, dx, gy, 1, colors->windowHighlight);
            drawHLine(d, ops, dx + 1, gy, 1, colors->windowShadow);
            drawHLine(d, ops, dx, gy + 1, 1, colors->windowHighlight);
            drawHLine(d, ops, dx + 1, gy + 1, 1, colors->windowShadow);
        }
    }
}


// ============================================================
// wgtSplitter
// ============================================================

WidgetT *wgtSplitter(WidgetT *parent, bool vertical) {
    WidgetT *w = widgetAlloc(parent, WidgetSplitterE);

    if (w) {
        w->as.splitter.vertical   = vertical;
        w->as.splitter.dividerPos = 0;
        w->weight = 100;
    }

    return w;
}


// ============================================================
// wgtSplitterGetPos
// ============================================================

int32_t wgtSplitterGetPos(const WidgetT *w) {
    return w->as.splitter.dividerPos;
}


// ============================================================
// wgtSplitterSetPos
// ============================================================

void wgtSplitterSetPos(WidgetT *w, int32_t pos) {
    w->as.splitter.dividerPos = pos;
    wgtInvalidate(w);
}