/*
 * meow_ui_box.c — 线性布局引擎（§12.1 meow_box）。
 *
 * meow_box 是**纯布局计算器**（非控件）：静态池创建、定长子项数组、arrange 单遍求解，
 * 把每个子控件的 x/y/w/h 写进 meow_widget（meow_widget_set_rect）；嵌套 sub-box 递归求解。
 * 用显式静态栈（深度≤MEOW_BOX_MAX_DEPTH）做嵌套展开，无 C 递归，杜绝栈爆炸。
 *
 * 求解模型（主轴向）：
 *   - 每个子项占位 = lead(margin) + extent + trail(margin)；项间再叠 box->gap。
 *   - FIXED/WRAP 的 extent 先定；WEIGHT 的 extent=0（待均分）。
 *   - leftover = content_main - foot；若权重和>0 → 均分 leftover；否则按主轴对齐分配。
 * 交叉轴：按 START/CENTER/END/STRETCH 对齐，STRETCH 填满容器交叉向减 margin。
 */
#include "meow_ui.h"
#include "include/meow_ui_box.h"
#include "meow_ui_internal.h"   /* meow_widget_rect（只读几何） */
#include <string.h>

#define MEOW_BOX_POOL 16        /* 静态池大小（并发 box 数） */

struct meow_box {
    int dir;                    /* MEOW_BOX_H / MEOW_BOX_V */
    int x, y, w, h;             /* 容器矩形（绝对坐标） */
    int pad_l, pad_t, pad_r, pad_b;
    int gap;
    int main_align;
    int cross_align;
    meow_box_item items[MEOW_BOX_MAX_CHILD];
    int n;
};

static meow_box g_pool[MEOW_BOX_POOL];
static unsigned char g_used[MEOW_BOX_POOL];

/* ---- 静态池存取 ---- */
meow_box *meow_box_new(meow_box_dir dir)
{
    for (int i = 0; i < MEOW_BOX_POOL; i++) {
        if (!g_used[i]) {
            g_used[i] = 1;
            meow_box *b = &g_pool[i];
            memset(b, 0, sizeof *b);
            b->dir = (dir == MEOW_BOX_H) ? MEOW_BOX_H : MEOW_BOX_V;
            return b;
        }
    }
    return NULL;
}
void meow_box_free(meow_box *b)
{
    if (!b) return;
    for (int i = 0; i < MEOW_BOX_POOL; i++)
        if (&g_pool[i] == b) { g_used[i] = 0; return; }
}

void meow_box_set_rect(meow_box *b, int x, int y, int w, int h)
{
    if (!b) return;
    b->x = x; b->y = y;
    b->w = w > 0 ? w : 0; b->h = h > 0 ? h : 0;
}
void meow_box_set_padding(meow_box *b, int l, int t, int r, int btm)
{
    if (!b) return;
    b->pad_l = l; b->pad_t = t; b->pad_r = r; b->pad_b = btm;
}
void meow_box_set_gap(meow_box *b, int gap)
{
    if (!b) return;
    b->gap = gap > 0 ? gap : 0;
}
void meow_box_set_align(meow_box *b, int main_align, int cross_align)
{
    if (!b) return;
    b->main_align = main_align;
    b->cross_align = cross_align;
}

/* ---- 子项 ---- */
int meow_box_add(meow_box *b, meow_widget *w, int size, int weight)
{
    return meow_box_add_ex(b, w, size, weight, 0, 0, NULL, NULL);
}
int meow_box_add_ex(meow_box *b, meow_widget *w, int size, int weight,
                    int min, int preferred, meow_box_measure_fn m, void *mctx)
{
    if (!b || !w || b->n >= MEOW_BOX_MAX_CHILD) return -1;
    if (size != MEOW_BOX_FIXED && size != MEOW_BOX_WEIGHT && size != MEOW_BOX_WRAP) return -1;
    if (size == MEOW_BOX_WEIGHT && weight <= 0) return -1;
    for (int i = 0; i < b->n; i++)
        if (b->items[i].w == w) return -1;   /* 同控件去重 */
    meow_box_item *it = &b->items[b->n++];
    memset(it, 0, sizeof *it);
    it->w = w; it->size = size; it->weight = weight > 0 ? weight : 1;
    it->min = min > 0 ? min : 0;
    it->preferred = preferred > 0 ? preferred : 0;
    it->measure = m; it->mctx = mctx;
    return 0;
}
int meow_box_add_sub(meow_box *b, meow_box *sub, int size, int weight)
{
    if (!b || !sub || b->n >= MEOW_BOX_MAX_CHILD) return -1;
    if (size != MEOW_BOX_FIXED && size != MEOW_BOX_WEIGHT && size != MEOW_BOX_WRAP) return -1;
    if (size == MEOW_BOX_WEIGHT && weight <= 0) return -1;
    for (int i = 0; i < b->n; i++)
        if (b->items[i].sub == sub) return -1;
    meow_box_item *it = &b->items[b->n++];
    memset(it, 0, sizeof *it);
    it->sub = sub; it->size = size; it->weight = weight > 0 ? weight : 1;
    return 0;
}

/* ---- 查询 ---- */
int meow_box_count(const meow_box *b) { return b ? b->n : 0; }
meow_widget *meow_box_widget_at(const meow_box *b, int idx)
{ return (b && idx >= 0 && idx < b->n) ? b->items[idx].w : NULL; }
meow_box *meow_box_sub_at(const meow_box *b, int idx)
{ return (b && idx >= 0 && idx < b->n) ? b->items[idx].sub : NULL; }
void meow_box_rect(const meow_box *b, int out[4])
{
    if (!out) return;
    if (!b) { out[0] = out[1] = out[2] = out[3] = 0; return; }
    out[0] = b->x; out[1] = b->y; out[2] = b->w; out[3] = b->h;
}

/* ---- 内部：取子项 margin（widget opts；sub 无 margin）---- */
static void item_margin(const meow_box_item *it, meow_box_dir dir,
                        int *main_before, int *main_after, int *cross)
{
    *main_before = *main_after = *cross = 0;
    if (!it->w) return;
    meow_widget_opts o;
    if (meow_widget_opts_get(it->w, &o) != 0) return;
    int mx = o.margin_x > 0 ? o.margin_x : 0;
    int my = o.margin_y > 0 ? o.margin_y : 0;
    if (dir == MEOW_BOX_H) { *main_before = mx; *main_after = mx; *cross = my; }
    else                   { *main_before = my; *main_after = my; *cross = mx; }
}

/* ---- 内部：子项主轴向 extent ----
 * FIXED  → 控件/嵌套盒当前主轴向尺寸
 * WRAP   → measure 回调（若有）否则控件当前尺寸；下限 clamp 到 min
 * WEIGHT → 0（由均分阶段填充） */
static int item_extent(const meow_box_item *it, int main_is_w)
{
    int extent = 0;
    if (it->w) {
        int r[4]; meow_widget_rect(it->w, r);
        extent = main_is_w ? r[2] : r[3];
    } else if (it->sub) {
        extent = main_is_w ? it->sub->w : it->sub->h;
    }
    if (it->size == MEOW_BOX_WRAP && it->measure) {
        int mn = 0, pf = 0;
        it->measure(it->mctx, &mn, &pf);
        if (pf > 0) extent = pf;
        else if (mn > 0) extent = mn;
        if (mn > 0 && extent < mn) extent = mn;   /* clamp 到下限 */
    }
    if (extent < 0) extent = 0;
    return extent;
}

/* ---- 单容器求解（一次 pass：算 extent + 位置，写全部子项矩形）----
 * 子项为嵌套 meow_box 时只写其矩形（父求结果），后续由 meow_box_arrange 的
 * 显式栈递归求解其内部。 */
static void box_layout_one(meow_box *b)
{
    int n = b->n;
    if (n <= 0) return;
    int cx = b->x + b->pad_l;
    int cy = b->y + b->pad_t;
    int cw = b->w - b->pad_l - b->pad_r; if (cw < 0) cw = 0;
    int ch = b->h - b->pad_t - b->pad_b; if (ch < 0) ch = 0;
    int main_is_w = (b->dir == MEOW_BOX_H);
    int main_size = main_is_w ? cw : ch;
    int cross_size = main_is_w ? ch : cw;
    int gap = b->gap;

    int ext[MEOW_BOX_MAX_CHILD], lead[MEOW_BOX_MAX_CHILD],
        trail[MEOW_BOX_MAX_CHILD], wgt[MEOW_BOX_MAX_CHILD];
    int nw = 0, wsum = 0;
    long long foot = 0;

    for (int i = 0; i < n; i++) {
        const meow_box_item *it = &b->items[i];
        int mb, ma, cr;
        item_margin(it, (meow_box_dir)b->dir, &mb, &ma, &cr);
        lead[i] = mb; trail[i] = ma; (void)cr;
        wgt[i] = (it->size == MEOW_BOX_WEIGHT) ? it->weight : 0;
        if (it->size == MEOW_BOX_WEIGHT) {
            ext[i] = 0; nw++; wsum += it->weight;
        } else {
            ext[i] = item_extent(it, main_is_w);
        }
        foot += (long long)lead[i] + trail[i] + ext[i];
    }
    foot += (long long)gap * (n - 1);

    long long leftover = (long long)main_size - foot;

    if (nw > 0 && leftover > 0) {
        /* 均分剩余到权重项；余数塞给最后一个权重项铺满精确 */
        long long consumed = 0;
        for (int i = 0; i < n; i++) {
            if (wgt[i] > 0) { ext[i] = (int)(leftover * wgt[i] / wsum); consumed += ext[i]; }
        }
        for (int i = n - 1; i >= 0; i--) {
            if (wgt[i] > 0) { ext[i] += (int)(leftover - consumed); break; }
        }
        leftover = 0;
    }

    /* 主轴对齐（仅当无权重、leftover != 0 有意义；有权重时 leftover≈0 → START 等效） */
    int off0 = 0;
    int intergap = gap;
    if (nw == 0) {
        if (leftover > 0) {
            switch (b->main_align) {
            case MEOW_BOX_ALIGN_CENTER:        off0 = (int)(leftover / 2); break;
            case MEOW_BOX_ALIGN_END:           off0 = (int)leftover; break;
            case MEOW_BOX_ALIGN_SPACE_BETWEEN: off0 = 0;
                intergap = (n > 1) ? gap + (int)(leftover / (n - 1)) : gap; break;
            case MEOW_BOX_ALIGN_SPACE_AROUND:  off0 = (int)(leftover / (2 * n));
                intergap = gap + (int)(leftover / n); break;
            case MEOW_BOX_ALIGN_SPACE_EVENLY:  off0 = (int)(leftover / (n + 1));
                intergap = gap + (int)(leftover / (n + 1)); break;
            default: off0 = 0; break;          /* START */
            }
        } else {
            off0 = 0; intergap = gap;          /* 溢出：从起点排（可越界，交滚动容器） */
        }
    }

    /* 主轴定位 + 交叉轴定位，写子控件矩形（主轴起点 = 内容原点 cx/cy）。
     * rel = 相对内容原点的主轴游标；content_rel = 本项内容相对起点；content_pos = 绝对主轴坐标。 */
    int main_base = main_is_w ? cx : cy;
    int rel = off0;
    for (int i = 0; i < n; i++) {
        const meow_box_item *it = &b->items[i];
        int content_rel = rel + lead[i];
        int content_pos = main_base + content_rel;
        if (it->w) {
            int r[4]; meow_widget_rect(it->w, r);
            meow_widget_opts o; int has = (meow_widget_opts_get(it->w, &o) == 0);
            int cmx = (has && o.margin_x > 0) ? o.margin_x : 0;
            int cmy = (has && o.margin_y > 0) ? o.margin_y : 0;
            int cm = main_is_w ? cmy : cmx;
            int base = main_is_w ? r[3] : r[2];
            int cross = 0, cross_ext = 0;
            if (b->cross_align == MEOW_BOX_CROSS_STRETCH) {
                cross_ext = cross_size - 2 * cm; if (cross_ext < 0) cross_ext = 0;
                cross = cm;
            } else {
                cross_ext = base;
                int pad = cross_size - 2 * cm - cross_ext; if (pad < 0) pad = 0;
                if (b->cross_align == MEOW_BOX_CROSS_CENTER) cross = cm + pad / 2;
                else if (b->cross_align == MEOW_BOX_CROSS_END) cross = cm + pad;
                else cross = cm;               /* START */
            }
            if (main_is_w)
                meow_widget_set_rect(it->w, content_pos, cy + cross, ext[i], cross_ext);
            else
                meow_widget_set_rect(it->w, cx + cross, content_pos, cross_ext, ext[i]);
        } else if (it->sub) {
            meow_box *sb = it->sub;
            int base = main_is_w ? sb->h : sb->w;
            int cross = 0, cross_ext = 0;
            if (b->cross_align == MEOW_BOX_CROSS_STRETCH) {
                cross_ext = cross_size; if (cross_ext < 0) cross_ext = 0;
                cross = 0;
            } else {
                cross_ext = base;
                int pad = cross_size - cross_ext; if (pad < 0) pad = 0;
                if (b->cross_align == MEOW_BOX_CROSS_CENTER) cross = pad / 2;
                else if (b->cross_align == MEOW_BOX_CROSS_END) cross = pad;
                else cross = 0;
            }
            if (main_is_w) { sb->x = content_pos; sb->y = cy + cross; sb->w = ext[i]; sb->h = cross_ext; }
            else           { sb->x = cx + cross; sb->y = content_pos; sb->w = cross_ext; sb->h = ext[i]; }
        }
        if (i < n - 1)
            rel = content_rel + ext[i] + trail[i] + intergap;
        else
            rel = content_rel + ext[i] + trail[i];
    }
}

/* ---- 求解：单遍，显式静态栈展开嵌套（深度≤MEOW_BOX_MAX_DEPTH）---- */
static meow_box *g_stack[MEOW_BOX_MAX_DEPTH];

void meow_box_arrange(meow_box *b)
{
    if (!b) return;
    int top = 0;
    g_stack[0] = b;
    while (top >= 0) {
        meow_box *cur = g_stack[top--];
        box_layout_one(cur);                       /* 写全部直接子项矩形（含 sub->rect） */
        for (int i = 0; i < cur->n; i++) {
            meow_box *sb = cur->items[i].sub;
            if (!sb) continue;
            if (top + 1 >= MEOW_BOX_MAX_DEPTH) continue;   /* 深度上限：跳过（矩形已被父写定） */
            g_stack[++top] = sb;
        }
    }
}