// widgetListBox.c  -- ListBox widget (single and multi-select)
//
// Scrollable list of text items with single-select or multi-select modes.
// Items are stored as external string pointers (not copied), with a vertical
// scrollbar appearing when the item count exceeds visible rows.
//
// Multi-select uses a parallel selBits array (one byte per item, 0 or 1)
// rather than a bitfield. Using a full byte per item wastes some memory but
// makes individual item toggle/test trivial without shift/mask operations,
// which matters when the selection code runs on every click and keyboard event.
//
// The selection model follows Windows explorer conventions:
//   - Plain click: select one item, clear others, set anchor
//   - Ctrl+click: toggle one item, update anchor
//   - Shift+click: range select from anchor to clicked item
//   - Shift+arrow: range select from anchor to cursor
//   - Space: toggle current item (multi-select)
//   - Ctrl+A: select all (multi-select)
//
// The "anchor" concept is key: it's the starting point for shift-select
// ranges. It's updated on non-shift clicks but stays fixed during shift
// operations, allowing the user to extend/shrink the selection by
// shift-clicking different endpoints.
//
// Drag-reorder support allows items to be rearranged by dragging. When
// enabled, a mouse-down initiates a drag (tracked via sDragReorder global),
// and a 2px horizontal line indicator shows the insertion point. The actual
// reordering is handled by the application's onReorder callback.

#include "widgetInternal.h"

#include <stdlib.h>
#include <string.h>

#define LISTBOX_PAD      2
#define LISTBOX_MIN_ROWS 4


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

static void allocSelBits(WidgetT *w);
static void ensureScrollVisible(WidgetT *w, int32_t idx);
static void selectRange(WidgetT *w, int32_t from, int32_t to);


// ============================================================
// allocSelBits
// ============================================================

// Allocate (or re-allocate) the selection bits array. Only allocated in
// multi-select mode  -- in single-select, selectedIdx alone tracks the
// selection. calloc initializes all bits to 0 (nothing selected).
static void allocSelBits(WidgetT *w) {
    if (w->as.listBox.selBits) {
        free(w->as.listBox.selBits);
        w->as.listBox.selBits = NULL;
    }

    int32_t count = w->as.listBox.itemCount;

    if (count > 0 && w->as.listBox.multiSelect) {
        w->as.listBox.selBits = (uint8_t *)calloc(count, 1);
    }
}


// ============================================================
// ensureScrollVisible
// ============================================================

// Adjust scroll position so the item at idx is within the visible viewport.
// If the item is above the viewport, scroll up to it. If below, scroll down
// to show it at the bottom. If already visible, do nothing.
static void ensureScrollVisible(WidgetT *w, int32_t idx) {
    if (idx < 0) {
        return;
    }

    AppContextT       *ctx  = wgtGetContext(w);
    const BitmapFontT *font = &ctx->font;
    int32_t innerH      = w->h - LISTBOX_BORDER * 2;
    int32_t visibleRows = innerH / font->charHeight;

    if (visibleRows < 1) {
        visibleRows = 1;
    }

    if (idx < w->as.listBox.scrollPos) {
        w->as.listBox.scrollPos = idx;
    } else if (idx >= w->as.listBox.scrollPos + visibleRows) {
        w->as.listBox.scrollPos = idx - visibleRows + 1;
    }
}


// ============================================================
// selectRange
// ============================================================

// Set selection bits for all items in the range [from, to] (inclusive,
// order-independent). Used for shift-click and shift-arrow range selection.
static void selectRange(WidgetT *w, int32_t from, int32_t to) {
    if (!w->as.listBox.selBits) {
        return;
    }

    int32_t lo = from < to ? from : to;
    int32_t hi = from > to ? from : to;

    if (lo < 0) {
        lo = 0;
    }

    if (hi >= w->as.listBox.itemCount) {
        hi = w->as.listBox.itemCount - 1;
    }

    for (int32_t i = lo; i <= hi; i++) {
        w->as.listBox.selBits[i] = 1;
    }
}


// ============================================================
// widgetListBoxDestroy
// ============================================================

void widgetListBoxDestroy(WidgetT *w) {
    if (w->as.listBox.selBits) {
        free(w->as.listBox.selBits);
        w->as.listBox.selBits = NULL;
    }
}


// ============================================================
// wgtListBox
// ============================================================

WidgetT *wgtListBox(WidgetT *parent) {
    WidgetT *w = widgetAlloc(parent, WidgetListBoxE);

    if (w) {
        w->as.listBox.selectedIdx = -1;
        w->as.listBox.anchorIdx   = -1;
        w->as.listBox.dragIdx     = -1;
        w->as.listBox.dropIdx     = -1;
    }

    return w;
}


// ============================================================
// wgtListBoxClearSelection
// ============================================================

void wgtListBoxClearSelection(WidgetT *w) {
    if (!w || w->type != WidgetListBoxE || !w->as.listBox.selBits) {
        return;
    }

    memset(w->as.listBox.selBits, 0, w->as.listBox.itemCount);
    wgtInvalidatePaint(w);
}


// ============================================================
// wgtListBoxGetSelected
// ============================================================

int32_t wgtListBoxGetSelected(const WidgetT *w) {
    VALIDATE_WIDGET(w, WidgetListBoxE, -1);

    return w->as.listBox.selectedIdx;
}


// ============================================================
// wgtListBoxIsItemSelected
// ============================================================

bool wgtListBoxIsItemSelected(const WidgetT *w, int32_t idx) {
    VALIDATE_WIDGET(w, WidgetListBoxE, false);

    if (!w->as.listBox.multiSelect) {
        return idx == w->as.listBox.selectedIdx;
    }

    if (!w->as.listBox.selBits || idx < 0 || idx >= w->as.listBox.itemCount) {
        return false;
    }

    return w->as.listBox.selBits[idx] != 0;
}


// ============================================================
// wgtListBoxSelectAll
// ============================================================

void wgtListBoxSelectAll(WidgetT *w) {
    if (!w || w->type != WidgetListBoxE || !w->as.listBox.selBits) {
        return;
    }

    memset(w->as.listBox.selBits, 1, w->as.listBox.itemCount);
    wgtInvalidatePaint(w);
}


// ============================================================
// wgtListBoxSetItemSelected
// ============================================================

void wgtListBoxSetItemSelected(WidgetT *w, int32_t idx, bool selected) {
    VALIDATE_WIDGET_VOID(w, WidgetListBoxE);

    if (!w->as.listBox.selBits || idx < 0 || idx >= w->as.listBox.itemCount) {
        return;
    }

    w->as.listBox.selBits[idx] = selected ? 1 : 0;
    wgtInvalidatePaint(w);
}


// ============================================================
// wgtListBoxSetItems
// ============================================================

void wgtListBoxSetItems(WidgetT *w, const char **items, int32_t count) {
    VALIDATE_WIDGET_VOID(w, WidgetListBoxE);

    w->as.listBox.items     = items;
    w->as.listBox.itemCount = count;

    // Cache max item strlen to avoid recomputing in calcMinSize
    int32_t maxLen = 0;

    for (int32_t i = 0; i < count; i++) {
        int32_t slen = (int32_t)strlen(items[i]);

        if (slen > maxLen) {
            maxLen = slen;
        }
    }

    w->as.listBox.maxItemLen = maxLen;

    if (w->as.listBox.selectedIdx >= count) {
        w->as.listBox.selectedIdx = count > 0 ? 0 : -1;
    }

    if (w->as.listBox.selectedIdx < 0 && count > 0) {
        w->as.listBox.selectedIdx = 0;
    }

    w->as.listBox.anchorIdx = w->as.listBox.selectedIdx;

    // Reallocate selection bits
    allocSelBits(w);

    // Pre-select the cursor item
    if (w->as.listBox.selBits && w->as.listBox.selectedIdx >= 0) {
        w->as.listBox.selBits[w->as.listBox.selectedIdx] = 1;
    }

    wgtInvalidate(w);
}


// ============================================================
// wgtListBoxSetReorderable
// ============================================================

void wgtListBoxSetReorderable(WidgetT *w, bool reorderable) {
    VALIDATE_WIDGET_VOID(w, WidgetListBoxE);

    w->as.listBox.reorderable = reorderable;
}


// ============================================================
// wgtListBoxSetMultiSelect
// ============================================================

void wgtListBoxSetMultiSelect(WidgetT *w, bool multi) {
    VALIDATE_WIDGET_VOID(w, WidgetListBoxE);

    w->as.listBox.multiSelect = multi;
    allocSelBits(w);

    // Sync: mark current selection
    if (w->as.listBox.selBits && w->as.listBox.selectedIdx >= 0) {
        w->as.listBox.selBits[w->as.listBox.selectedIdx] = 1;
    }
}


// ============================================================
// wgtListBoxSetSelected
// ============================================================

void wgtListBoxSetSelected(WidgetT *w, int32_t idx) {
    VALIDATE_WIDGET_VOID(w, WidgetListBoxE);

    w->as.listBox.selectedIdx = idx;
    w->as.listBox.anchorIdx   = idx;

    // In multi-select, clear all then select just this one
    if (w->as.listBox.selBits) {
        memset(w->as.listBox.selBits, 0, w->as.listBox.itemCount);

        if (idx >= 0 && idx < w->as.listBox.itemCount) {
            w->as.listBox.selBits[idx] = 1;
        }
    }

    wgtInvalidatePaint(w);
}


// ============================================================
// widgetListBoxCalcMinSize
// ============================================================

// Min size accounts for the widest item, a scrollbar, padding, and border.
// Height is based on LISTBOX_MIN_ROWS (4 rows) so the listbox has a usable
// minimum height even when empty. The 8-character minimum width prevents
// the listbox from collapsing too narrow when items are short or absent.
void widgetListBoxCalcMinSize(WidgetT *w, const BitmapFontT *font) {
    int32_t maxItemW = w->as.listBox.maxItemLen * font->charWidth;
    int32_t minW     = font->charWidth * 8;

    if (maxItemW < minW) {
        maxItemW = minW;
    }

    w->calcMinW = maxItemW + LISTBOX_PAD * 2 + LISTBOX_BORDER * 2 + WGT_SB_W;
    w->calcMinH = LISTBOX_MIN_ROWS * font->charHeight + LISTBOX_BORDER * 2;
}


// ============================================================
// widgetListBoxOnKey
// ============================================================

// Key handling: delegates to widgetNavigateIndex for cursor movement
// (Up, Down, Home, End, PgUp, PgDn) which returns the new index after
// navigation. This shared helper ensures consistent keyboard navigation
// across ListBox, ListView, and other scrollable widgets.
void widgetListBoxOnKey(WidgetT *w, int32_t key, int32_t mod) {
    if (!w || w->type != WidgetListBoxE || w->as.listBox.itemCount == 0) {
        return;
    }

    bool    multi = w->as.listBox.multiSelect;
    bool    shift = (mod & KEY_MOD_SHIFT) != 0;
    bool    ctrl  = (mod & KEY_MOD_CTRL) != 0;
    int32_t sel   = w->as.listBox.selectedIdx;

    // Ctrl+A  -- select all (multi-select only)
    if (multi && ctrl && (key == 'a' || key == 'A' || key == 1)) {
        wgtListBoxSelectAll(w);
        return;
    }

    // Space  -- toggle current item (multi-select only)
    if (multi && key == ' ') {
        if (sel >= 0 && w->as.listBox.selBits) {
            w->as.listBox.selBits[sel] ^= 1;
            w->as.listBox.anchorIdx = sel;
        }

        if (w->onChange) {
            w->onChange(w);
        }

        wgtInvalidatePaint(w);
        return;
    }

    // Enter  -- activate selected item (same as double-click)
    if (key == '\r' || key == '\n') {
        if (w->onDblClick && sel >= 0) {
            w->onDblClick(w);
        }

        return;
    }

    AppContextT       *ctx  = wgtGetContext(w);
    const BitmapFontT *font = &ctx->font;
    int32_t visibleRows = (w->h - LISTBOX_BORDER * 2) / font->charHeight;

    if (visibleRows < 1) {
        visibleRows = 1;
    }

    int32_t newSel = widgetNavigateIndex(key, sel, w->as.listBox.itemCount, visibleRows);

    if (newSel < 0) {
        return;
    }

    if (newSel == sel) {
        return;
    }

    w->as.listBox.selectedIdx = newSel;

    // Update selection
    if (multi && w->as.listBox.selBits) {
        if (shift) {
            // Shift+arrow: range from anchor to new cursor
            memset(w->as.listBox.selBits, 0, w->as.listBox.itemCount);
            selectRange(w, w->as.listBox.anchorIdx, newSel);
        }
        // Plain arrow: just move cursor, leave selections untouched
    }

    ensureScrollVisible(w, newSel);

    if (w->onChange) {
        w->onChange(w);
    }

    wgtInvalidatePaint(w);
}


// ============================================================
// widgetListBoxOnMouse
// ============================================================

// Mouse handling: first checks if the click is on the scrollbar (right edge),
// then falls through to item click handling. The scrollbar hit-test uses
// widgetScrollbarHitTest which divides the scrollbar into arrow buttons, page
// regions, and thumb based on the click position. Item clicks are translated
// from pixel coordinates to item index using integer division by charHeight.
void widgetListBoxOnMouse(WidgetT *hit, WidgetT *root, int32_t vx, int32_t vy) {
    AppContextT       *ctx  = (AppContextT *)root->userData;
    const BitmapFontT *font = &ctx->font;

    int32_t innerH      = hit->h - LISTBOX_BORDER * 2;
    int32_t visibleRows = innerH / font->charHeight;
    bool    needSb      = (hit->as.listBox.itemCount > visibleRows);

    // Clamp scroll
    int32_t maxScroll = hit->as.listBox.itemCount - visibleRows;

    if (maxScroll < 0) {
        maxScroll = 0;
    }

    hit->as.listBox.scrollPos = clampInt(hit->as.listBox.scrollPos, 0, maxScroll);

    // Check if click is on the scrollbar
    if (needSb) {
        int32_t sbX = hit->x + hit->w - LISTBOX_BORDER - WGT_SB_W;

        if (vx >= sbX) {
            int32_t    relY = vy - (hit->y + LISTBOX_BORDER);
            ScrollHitE sh   = widgetScrollbarHitTest(innerH, relY, hit->as.listBox.itemCount, visibleRows, hit->as.listBox.scrollPos);

            if (sh == ScrollHitArrowDecE) {
                if (hit->as.listBox.scrollPos > 0) {
                    hit->as.listBox.scrollPos--;
                }
            } else if (sh == ScrollHitArrowIncE) {
                if (hit->as.listBox.scrollPos < maxScroll) {
                    hit->as.listBox.scrollPos++;
                }
            } else if (sh == ScrollHitPageDecE) {
                hit->as.listBox.scrollPos -= visibleRows;
                hit->as.listBox.scrollPos = clampInt(hit->as.listBox.scrollPos, 0, maxScroll);
            } else if (sh == ScrollHitPageIncE) {
                hit->as.listBox.scrollPos += visibleRows;
                hit->as.listBox.scrollPos = clampInt(hit->as.listBox.scrollPos, 0, maxScroll);
            } else if (sh == ScrollHitThumbE) {
                int32_t trackLen  = innerH - WGT_SB_W * 2;
                int32_t thumbPos;
                int32_t thumbSize;
                widgetScrollbarThumb(trackLen, hit->as.listBox.itemCount, visibleRows, hit->as.listBox.scrollPos, &thumbPos, &thumbSize);

                sDragScrollbar      = hit;
                sDragScrollbarOrient = 0;
                sDragScrollbarOff   = relY - WGT_SB_W - thumbPos;
            }

            hit->focused = true;
            return;
        }
    }

    // Click on item area
    int32_t innerY = hit->y + LISTBOX_BORDER;
    int32_t relY   = vy - innerY;

    if (relY < 0) {
        return;
    }

    int32_t clickedRow = relY / font->charHeight;
    int32_t idx        = hit->as.listBox.scrollPos + clickedRow;

    if (idx < 0 || idx >= hit->as.listBox.itemCount) {
        return;
    }

    bool multi = hit->as.listBox.multiSelect;
    bool shift = (ctx->keyModifiers & KEY_MOD_SHIFT) != 0;
    bool ctrl  = (ctx->keyModifiers & KEY_MOD_CTRL) != 0;

    hit->as.listBox.selectedIdx = idx;
    hit->focused = true;

    if (multi && hit->as.listBox.selBits) {
        if (ctrl) {
            // Ctrl+click: toggle item, update anchor
            hit->as.listBox.selBits[idx] ^= 1;
            hit->as.listBox.anchorIdx = idx;
        } else if (shift) {
            // Shift+click: range from anchor to clicked
            memset(hit->as.listBox.selBits, 0, hit->as.listBox.itemCount);
            selectRange(hit, hit->as.listBox.anchorIdx, idx);
        } else {
            // Plain click: select only this item, update anchor
            memset(hit->as.listBox.selBits, 0, hit->as.listBox.itemCount);
            hit->as.listBox.selBits[idx] = 1;
            hit->as.listBox.anchorIdx = idx;
        }
    }

    if (hit->onChange) {
        hit->onChange(hit);
    }

    // onDblClick is handled by the central dispatcher in widgetEvent.c

    // Initiate drag-reorder if enabled (not from modifier clicks)
    if (hit->as.listBox.reorderable && !shift && !ctrl) {
        hit->as.listBox.dragIdx = idx;
        hit->as.listBox.dropIdx = idx;
        sDragReorder = hit;
    }
}


// ============================================================
// widgetListBoxPaint
// ============================================================

// Paint: sunken bevel border, then iterate visible rows drawing text.
// Selected items get highlight background (full row width) with contrasting
// text color. In multi-select mode, the cursor item (selectedIdx) gets a
// dotted focus rect overlay  -- this is separate from the selection highlight
// so the user can see which item the keyboard cursor is on even when multiple
// items are selected. The scrollbar is drawn only when needed (item count
// exceeds visible rows), and the content width is reduced accordingly.
void widgetListBoxPaint(WidgetT *w, DisplayT *d, const BlitOpsT *ops, const BitmapFontT *font, const ColorSchemeT *colors) {
    uint32_t fg = w->fgColor ? w->fgColor : colors->contentFg;
    uint32_t bg = w->bgColor ? w->bgColor : colors->contentBg;

    int32_t innerH      = w->h - LISTBOX_BORDER * 2;
    int32_t visibleRows = innerH / font->charHeight;
    bool    needSb      = (w->as.listBox.itemCount > visibleRows);
    int32_t contentW    = w->w - LISTBOX_BORDER * 2;

    if (needSb) {
        contentW -= WGT_SB_W;
    }

    // Sunken border
    BevelStyleT bevel = BEVEL_SUNKEN(colors, bg, 2);
    drawBevel(d, ops, w->x, w->y, w->w, w->h, &bevel);

    // Clamp scroll position
    int32_t maxScroll = w->as.listBox.itemCount - visibleRows;

    if (maxScroll < 0) {
        maxScroll = 0;
    }

    w->as.listBox.scrollPos = clampInt(w->as.listBox.scrollPos, 0, maxScroll);

    // Draw items
    int32_t  innerX    = w->x + LISTBOX_BORDER + LISTBOX_PAD;
    int32_t  innerY    = w->y + LISTBOX_BORDER;
    int32_t  scrollPos = w->as.listBox.scrollPos;
    bool     multi     = w->as.listBox.multiSelect;
    uint8_t *selBits   = w->as.listBox.selBits;

    for (int32_t i = 0; i < visibleRows && (scrollPos + i) < w->as.listBox.itemCount; i++) {
        int32_t  idx = scrollPos + i;
        int32_t  iy  = innerY + i * font->charHeight;
        uint32_t ifg = fg;
        uint32_t ibg = bg;

        bool isSelected;

        if (multi && selBits) {
            isSelected = selBits[idx] != 0;
        } else {
            isSelected = (idx == w->as.listBox.selectedIdx);
        }

        if (isSelected) {
            ifg = colors->menuHighlightFg;
            ibg = colors->menuHighlightBg;
            rectFill(d, ops, w->x + LISTBOX_BORDER, iy, contentW, font->charHeight, ibg);
        }

        drawText(d, ops, font, innerX, iy, w->as.listBox.items[idx], ifg, ibg, false);

        // Draw cursor indicator in multi-select (dotted focus rect on cursor item)
        if (multi && idx == w->as.listBox.selectedIdx && w->focused) {
            drawFocusRect(d, ops, w->x + LISTBOX_BORDER, iy, contentW, font->charHeight, fg);
        }
    }

    // Draw drag-reorder insertion indicator: a 2px horizontal line at the
    // drop position. The line is drawn between items (not on top of them)
    // so it's clear where the dragged item will be inserted.
    if (w->as.listBox.reorderable && w->as.listBox.dragIdx >= 0 && w->as.listBox.dropIdx >= 0) {
        int32_t drop  = w->as.listBox.dropIdx;
        int32_t lineY = innerY + (drop - scrollPos) * font->charHeight;

        if (lineY >= innerY && lineY <= innerY + innerH) {
            drawHLine(d, ops, w->x + LISTBOX_BORDER, lineY, contentW, colors->contentFg);
            drawHLine(d, ops, w->x + LISTBOX_BORDER, lineY + 1, contentW, colors->contentFg);
        }
    }

    // Draw scrollbar
    if (needSb) {
        int32_t sbX = w->x + w->w - LISTBOX_BORDER - WGT_SB_W;
        int32_t sbY = w->y + LISTBOX_BORDER;
        widgetDrawScrollbarV(d, ops, colors, sbX, sbY, innerH, w->as.listBox.itemCount, visibleRows, w->as.listBox.scrollPos);
    }

    if (w->focused) {
        drawFocusRect(d, ops, w->x + 1, w->y + 1, w->w - 2, w->h - 2, fg);
    }
}