/* app/shelf_model.c — 书架数据模型实现（见 app/shelf_model.h）。 */
#include "shelf_model.h"

#include <dirent.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>

int shelf_fmt_from_ext(const char *name)
{
    const char *d = strrchr(name, '.');
    if (!d) return -1;
    if (strcasecmp(d, ".txt") == 0) return 0;
    if (strcasecmp(d, ".fb2") == 0) return 1;
    if (strcasecmp(d, ".epub") == 0) return 2;
    if (strcasecmp(d, ".mobi") == 0) return 3;
    if (strcasecmp(d, ".cbz") == 0) return 4;
    return -1;
}

const char *shelf_fmt_name(int f)
{
    switch (f) {
        case 0: return "TXT";
        case 1: return "FB2";
        case 2: return "EPUB";
        case 3: return "MOBI";
        case 4: return "CBZ";
        default: return "?";
    }
}

void shelf_fmt_size(char *out, int outsz, long size)
{
    if (!out || outsz <= 0) return;
    if (size >= 1 << 20) snprintf(out, (size_t)outsz, "%.1fMB", (double)size / (1 << 20));
    else if (size >= 1 << 10) snprintf(out, (size_t)outsz, "%.0fKB", (double)size / (1 << 10));
    else snprintf(out, (size_t)outsz, "%ldB", size);
}

int shelf_copy_utf8(char *dst, int cap, const char *src)
{
    if (!dst || cap <= 0) return 0;
    if (!src) { dst[0] = 0; return 0; }
    int limit = cap - 1;
    int n = 0;
    while (src[n] && n < limit) n++;
    if (src[n]) {
        /* 截断：若 src[n] 是续字节（10xxxxxx），回退到该字符首字节之前，整段丢弃。 */
        while (n > 0 && ((unsigned char)src[n] & 0xC0) == 0x80) n--;
    }
    memcpy(dst, src, (size_t)n);
    dst[n] = 0;
    return n;
}

static int cmp_recent_then_name(const void *a, const void *b)
{
    const shelf_book *x = (const shelf_book *)a, *y = (const shelf_book *)b;
    if (x->ts != y->ts) return (x->ts < y->ts) ? 1 : -1;   /* 最近在前 */
    return strcasecmp(x->title, y->title);
}

/* 最近阅读排序（扫描后 / 刚读完置顶共用同一口径）。 */
void shelf_sort_recent(shelf_book *books, int nbooks)
{
    if (!books || nbooks < 2) return;
    qsort(books, (size_t)nbooks, sizeof(shelf_book), cmp_recent_then_name);
}

/* 重建一本书的两种副题（扫描后与「刚读完置顶」共用同一份格式化逻辑）。
 *   sub        = 格式 · 大小 [· 读]（format 模式/宫格）
 *   sub_folder = 相对 book.group 第一级之后的子路径 · sub（folder 模式）
 */
void shelf_fmt_sub(shelf_book *b)
{
    if (!b) return;
    char sz[24];
    shelf_fmt_size(sz, sizeof sz, b->size);
    /* 默认副题：与 M27 前逐字一致（format 模式/宫格都用它）。 */
    snprintf(b->sub, sizeof b->sub, "%s  ·  %s%s", shelf_fmt_name(b->fmt), sz,
             b->ts ? "  ·  读" : "");
    /* folder 副题：第一级之后的子路径（分类/作品）前置，其余同默认副题。 */
    const char *rest = strchr(b->group, '/');
    if (rest) rest++;
    if (rest && rest[0]) {
        char pre[100];
        shelf_copy_utf8(pre, (int)sizeof pre, rest);
        snprintf(b->sub_folder, sizeof b->sub_folder, "%s  ·  %s", pre, b->sub);
    } else {
        snprintf(b->sub_folder, sizeof b->sub_folder, "%s", b->sub);
    }
}

typedef struct scan_ctx {
    shelf_book    *books;
    int            cap;
    int            n;
    int            truncated;
    int            depth_skipped;
    shelf_ts_fn    ts_fn;
} scan_ctx;

/* 统计 dir 子树里还能识别的书籍文件数（只数不收集）。自身留 8 层硬上限，
 * 防符号链接/异常深目录把计数也拖死。返回书籍文件数。 */
static int count_books_under(const char *dir, int depth)
{
    if (depth > SHELF_SCAN_MAX_DEPTH + 8) return 0;
    int n = 0;
    DIR *dp = opendir(dir);
    if (!dp) return 0;
    struct dirent *de;
    while ((de = readdir(dp))) {
        if (de->d_name[0] == '.') continue;
        char path[400];
        if (snprintf(path, sizeof path, "%s/%s", dir, de->d_name) >= (int)sizeof path) continue;
        struct stat st;
        if (stat(path, &st) != 0) continue;
        if (S_ISDIR(st.st_mode)) { n += count_books_under(path, depth + 1); continue; }
        if (shelf_fmt_from_ext(de->d_name) >= 0) n++;
    }
    closedir(dp);
    return n;
}

/* 递归收集。rel = 相对 root 的完整目录路径（root 自身为 ""），
 * top = 第一级目录名（root 自身/根下文件为 ""）。 */
static void scan_dir(scan_ctx *c, const char *dir, int depth, const char *rel, const char *top)
{
    if (depth > SHELF_SCAN_MAX_DEPTH) return;   /* 防深嵌套/循环 */
    if (c->n >= c->cap) return;                 /* 已满：不再进新目录 */
    DIR *dp = opendir(dir);
    if (!dp) return;
    struct dirent *de;
    while ((de = readdir(dp))) {
        if (de->d_name[0] == '.') continue;
        char path[400];
        if (snprintf(path, sizeof path, "%s/%s", dir, de->d_name) >= (int)sizeof path) continue;
        struct stat st;
        if (stat(path, &st) != 0) continue;
        if (S_ISDIR(st.st_mode)) {
            if (depth + 1 > SHELF_SCAN_MAX_DEPTH) {
                c->depth_skipped += count_books_under(path, depth + 1);   /* 超深：计数→可见提示 */
                continue;
            }
            if (c->n >= c->cap) {
                /* 上限卡在目录边界：探一下这个子树是否真有书，有书才算被截断。
                 * 只探空目录不置位，避免“正好装满且后面全是空目录”误报。 */
                if (!c->truncated && count_books_under(path, depth + 1) > 0) c->truncated = 1;
                if (c->truncated) break;   /* 已确认丢书，后面的目录/文件不必再跑 */
                continue;
            }
            char subrel[SHELF_GROUP_MAX * 16];
            snprintf(subrel, sizeof subrel, "%s%s%s", rel, rel[0] ? "/" : "", de->d_name);
            /* 第一级目录名 = top；更深层沿用。de->d_name 在递归返回前有效。 */
            scan_dir(c, path, depth + 1, subrel, depth == 0 ? de->d_name : top);
            continue;
        }
        int f = shelf_fmt_from_ext(de->d_name);
        if (f < 0) continue;
        if (c->n >= c->cap) { c->truncated = 1; break; }   /* 超限：可见提示，不静默 */
        shelf_book *b = &c->books[c->n];
        shelf_copy_utf8(b->path, (int)sizeof b->path, path);
        shelf_copy_utf8(b->title, (int)sizeof b->title, de->d_name);
        char *dot = strrchr(b->title, '.');
        if (dot) *dot = 0;                     /* 标题去扩展名 */
        shelf_copy_utf8(b->group, (int)sizeof b->group, rel);
        shelf_copy_utf8(b->top, (int)sizeof b->top, top);
        b->fmt = f;
        b->size = (long)st.st_size;
        b->ts = c->ts_fn ? c->ts_fn(b->path) : 0;
        shelf_fmt_sub(b);   /* 副题：格式 · 大小 [· 读]（+ folder 子路径） */
        c->n++;
    }
    closedir(dp);
}

int shelf_scan_books(const char *root, shelf_book *books, int cap,
                     shelf_ts_fn ts_fn, shelf_scan_report *rep)
{
    if (rep) { rep->nbooks = 0; rep->truncated = 0; rep->depth_skipped = 0; rep->root_missing = 0; }
    if (!root || !books || cap <= 0) {
        if (rep) rep->root_missing = 1;
        return 0;
    }
    DIR *dp = opendir(root);
    if (!dp) {
        if (rep) rep->root_missing = 1;
        return 0;
    }
    closedir(dp);

    scan_ctx c;
    c.books = books; c.cap = cap; c.n = 0; c.truncated = 0; c.depth_skipped = 0; c.ts_fn = ts_fn;
    scan_dir(&c, root, 0, "", "");
    shelf_sort_recent(books, c.n);
    if (rep) {
        rep->nbooks = c.n;
        rep->truncated = c.truncated;
        rep->depth_skipped = c.depth_skipped;
    }
    return c.n;
}

/* ---- 行序列 ---- */

/* 分组键 = top（Books 第一级目录名）。长度截到第一个 '/'，排序时忽略大小写。 */
static int top_len(const char *s)
{
    const char *p = strchr(s, '/');
    return p ? (int)(p - s) : (int)strlen(s);
}
static int top_cmp(const char *a, const char *b)
{
    int la = top_len(a), lb = top_len(b);
    if (!la != !lb) return la ? 1 : -1;         /* 根组 "" 恒置顶 */
    int m = la < lb ? la : lb;
    int c = strncasecmp(a, b, (size_t)m);
    if (c) return c;
    return la - lb;
}
static int top_eq(const char *a, const char *b) { return top_cmp(a, b) == 0; }

/* 段头排序：根组（top==""）恒置顶，其余按第一级目录名不区分大小写排序。 */
static int cmp_group_key(const void *pa, const void *pb)
{
    return top_cmp(*(const char *const *)pa, *(const char *const *)pb);
}

static int build_rows_format(const shelf_book *books, int nbooks,
                             shelf_row *rows, int rowcap)
{
    static const int fmts[] = { 0, 1, 2, 3, 4 };
    int nrows = 0;
    for (size_t fi = 0; fi < sizeof fmts / sizeof fmts[0]; fi++) {
        int fmt = fmts[fi];
        int have = 0;
        if (nrows >= rowcap) break;
        for (int i = 0; i < nbooks; i++) {
            if (books[i].fmt != fmt) continue;
            if (!have) {
                if (nrows >= rowcap) break;
                rows[nrows].section = 1; rows[nrows].fmt = fmt;
                rows[nrows].book = -1;   rows[nrows].label = NULL;
                nrows++;
                have = 1;
            }
            if (nrows >= rowcap) break;
            rows[nrows].section = 0; rows[nrows].fmt = fmt;
            rows[nrows].book = i;    rows[nrows].label = NULL;
            nrows++;
        }
    }
    return nrows;
}

static int build_rows_folder(const shelf_book *books, int nbooks,
                             shelf_row *rows, int rowcap)
{
    /* 去重分组键（books[].top，""=根组）。键指向 books 内字符串，生存期覆盖 rows。 */
    static const char *keys[SHELF_MAX_BOOKS];
    int nkeys = 0;
    for (int i = 0; i < nbooks; i++) {
        const char *k = books[i].top;
        int seen = 0;
        for (int j = 0; j < nkeys; j++) {
            if (top_eq(keys[j], k)) { seen = 1; break; }
        }
        if (!seen) keys[nkeys++] = k;
    }
    qsort(keys, (size_t)nkeys, sizeof keys[0], cmp_group_key);

    int nrows = 0;
    for (int ki = 0; ki < nkeys; ki++) {
        if (nrows >= rowcap) break;
        rows[nrows].section = 1;
        rows[nrows].fmt = -1;
        rows[nrows].book = -1;
        rows[nrows].label = keys[ki][0] ? keys[ki] : SHELF_GROUP_ROOT;
        nrows++;
        for (int i = 0; i < nbooks; i++) {
            if (!top_eq(books[i].top, keys[ki])) continue;
            if (nrows >= rowcap) break;
            rows[nrows].section = 0;
            rows[nrows].fmt = books[i].fmt;
            rows[nrows].book = i;
            rows[nrows].label = NULL;
            nrows++;
        }
    }
    return nrows;
}

int shelf_build_rows(const shelf_book *books, int nbooks, int folder_mode,
                     shelf_row *rows, int rowcap)
{
    if (!books || !rows || nbooks <= 0 || rowcap <= 0) return 0;
    if (nbooks > SHELF_MAX_BOOKS) nbooks = SHELF_MAX_BOOKS;
    return folder_mode ? build_rows_folder(books, nbooks, rows, rowcap)
                       : build_rows_format(books, nbooks, rows, rowcap);
}