/* app/book.c — 书桥实现（见 app/book.h）：把 rd_src（TXT/FB2/EPUB/MOBI 段契约 + CBZ 图页）
 * + engine(FreeType/rdimg) 串成「一本书」。
 *
 * 文本格式：build_index 逐段 rd_src_next → 每段 utf8→码点→rd_layout → 页索引（flat：段+段内字符偏移）
 * （即 rdtxt 同款 UTF-8 段契约喂排版器）；渲染按段重显。锚定 (段,字符偏移) 与字号无关。
 * CBZ：纯图页，npages=图片数，render 用 rdimg 解码+降采样写内容区。
 */
#include "book.h"
#include "rdsrc.h"
#include "rdtxt.h"
#include "seg.h"
#include "rdlayout.h"
#include "rdimg.h"
#include "../engine/rdft.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>

typedef struct seg {
    int page_start;   /* 全局页表起点 */
    int page_count;   /* 本段页数 */
} seg_t;

struct rd_book {
    char        path[400];
    char        font[400];
    char        base[256];
    const char *encname;   /* TXT 有效编码可读名（含覆盖后）；非 TXT = "" */
    rd_enc_t    enc;       /* TXT 有效编码；非 TXT = RD_ENC_UTF8 */
    rdft       *ft;
    rd_src     *src;
    rd_fmt_t    fmt;
    int         is_img;   /* 1=CBZ 图片书 */

    int fs, ls, pw, ph, mx, my, top;
    int content_w, content_h;

    seg_t        *segs;  int nsegs;
    rd_book_page *pages; int npages;   /* flat 页表（文本） */
    int          cur;

    /* 当前渲染段复用缓冲 */
    uint8_t  *seg_utf8;  size_t seg_utf8_cap;
    uint32_t *seg_cps;   size_t seg_cps_n, seg_cps_cap;
    rd_line  *seg_lines; rd_page *seg_pages; int seg_nlines, seg_npages;
    int      seg_cache_idx;

    /* R3.2 分段流式（TXT）：段目录 + 全局段数 + 已建段数 + 段/页表容量（增量补齐用） */
    char     seg_dir[400];
    int      seg_n;        /* 段文件总数（manifest）；fallback = nsegs（全建） */
    int      seg_built;    /* 已布局段数；fallback = nsegs */
    int      segs_cap, pages_cap;   /* segs[]/pages[] 当前容量（只在 seg 路径增量增长） */
};

/* ---- 页索引持久化（MeowData；见 rd_book_set_index_dir） ----
 * build_index 对整书逐段 reflow 建 flat 页表，是开大书最贵的步骤（无持久化时每次打开都重跑）。
 * 宿主快 ≠ 真机快：同一书 MIPS 上仍需数秒。这里把 (segs + pages) 落盘成 {path 哈希}.idx，
 * 以 (file_size, file_mtime, font path+mt, fs, ls, content_w, content_h, enc) 为失效键——
 * 书/字号/行距/版面/编码/字体任一变了即自动重排并重写，其余情况命中缓存秒开。
 * 纯 libc（无 SDK）：reader.c 用 meow_config_dir 推导 MeowData dir 注入；冒烟/无卡时 dir 为空 → 直排不持久。 */

static char g_index_dir[400];   /* 索引缓存目录; 空 = 禁用 */
void rd_book_set_index_dir(const char *dir)
{
    if (dir && dir[0]) { strncpy(g_index_dir, dir, sizeof g_index_dir - 1); g_index_dir[sizeof g_index_dir - 1] = 0; }
    else g_index_dir[0] = 0;
}

/* R3.2：分段流式缓存根（MeowData/os.meow.reader）。存到 g_seg_base 并同步 rdseg。 */
static char g_seg_base[400];
void rd_book_set_seg_base(const char *base)
{
    if (base && base[0]) { strncpy(g_seg_base, base, sizeof g_seg_base - 1); g_seg_base[sizeof g_seg_base - 1] = 0; }
    else g_seg_base[0] = 0;
    rdseg_set_base(g_seg_base);
}

#define IDX_MAGIC0 'R'
#define IDX_MAGIC1 'I'
#define IDX_MAGIC2 'D'
#define IDX_MAGIC3 'X'
#define IDX_VER     1u

static int fio_rd(FILE *f, void *p, size_t n) { return fread(p, 1, n, f) == n; }
static int fio_wr(FILE *f, const void *p, size_t n) { return fwrite(p, 1, n, f) == n; }

static uint32_t idx_fnv1a(const char *s)
{
    uint32_t h = 2166136261u;
    for (const unsigned char *p = (const unsigned char *)s; *p; p++) { h ^= *p; h *= 16777619u; }
    return h;
}
static int index_cache_path(const rd_book *b, char *out, int outsz)
{
    if (!g_index_dir[0]) return -1;
    if (snprintf(out, (size_t)outsz, "%s/%08x.idx", g_index_dir, idx_fnv1a(b->path)) >= outsz) return -1;
    return 0;
}

/* 编码枚举 → 可读名（R3：Big5 正确解码后名实相符）。 */
static const char *enc_to_name(rd_enc_t enc)
{
    switch (enc) {
        case RD_ENC_UTF8: return "UTF-8";
        case RD_ENC_UTF16LE: return "UTF-16LE";
        case RD_ENC_UTF16BE: return "UTF-16BE";
        case RD_ENC_GB18030: return "GB18030";
        case RD_ENC_BIG5: return "Big5";
        case RD_ENC_ASCII: return "ASCII";
        default: return "";
    }
}
static const char *fmt_encname(rd_fmt_t f, rd_enc_t enc)
{
    if (f == RD_FMT_TXT) return enc_to_name(enc);
    return "";
}

static int book_meas(uint32_t cp, int fs, int *adv, void *ctx)
{
    (void)fs;
    rd_book *b = (rd_book *)ctx;
    return rdft_advance(b->ft, cp, adv);
}

/* 失效键：书 + 版面 + 编码 + 字体。任一变化 → 缓存不命中（重排）。 */
typedef struct {
    uint64_t file_size;
    int64_t  file_mtime;
    int64_t  font_mtime;   /* 字体文件 mtime；无字体(近似测宽) = 0 */
    int32_t  fs, ls, cw, ch, enc;
    char     font[320];
} idx_key;

static int index_key_fill(rd_book *b, idx_key *k)
{
    memset(k, 0, sizeof *k);
    struct stat st;
    if (stat(b->path, &st) != 0) { k->file_size = 0; k->file_mtime = 0; }
    else { k->file_size = (uint64_t)st.st_size; k->file_mtime = (int64_t)st.st_mtime; }
    if (b->font[0]) {
        /* b->font[400] 已 NUL 结尾（open 时 <400 才收）；memcpy 319B 恒在界内且 k 已清零 → 余下为 0 */
        memcpy(k->font, b->font, sizeof k->font - 1);
        struct stat fs2;
        if (stat(b->font, &fs2) == 0) k->font_mtime = (int64_t)fs2.st_mtime;
    }
    k->fs = b->fs; k->ls = b->ls; k->cw = b->content_w; k->ch = b->content_h;
    k->enc = (int32_t)b->enc;
    return 0;
}

static int index_key_write(const idx_key *k, FILE *f)
{
    const uint8_t magic[4] = { IDX_MAGIC0, IDX_MAGIC1, IDX_MAGIC2, IDX_MAGIC3 };
    uint16_t ver = IDX_VER;
    return fio_wr(f, magic, sizeof magic) && fio_wr(f, &ver, sizeof ver) &&
           fio_wr(f, &k->file_size, sizeof k->file_size) &&
           fio_wr(f, &k->file_mtime, sizeof k->file_mtime) && fio_wr(f, &k->font_mtime, sizeof k->font_mtime) &&
           fio_wr(f, &k->fs, sizeof k->fs) && fio_wr(f, &k->ls, sizeof k->ls) &&
           fio_wr(f, &k->cw, sizeof k->cw) && fio_wr(f, &k->ch, sizeof k->ch) &&
           fio_wr(f, &k->enc, sizeof k->enc) && fio_wr(f, k->font, sizeof k->font);
}
static int index_key_read(idx_key *k, FILE *f)
{
    uint8_t magic[4];
    if (!fio_rd(f, magic, sizeof magic)) return 0;
    if (magic[0] != IDX_MAGIC0 || magic[1] != IDX_MAGIC1 || magic[2] != IDX_MAGIC2 || magic[3] != IDX_MAGIC3) return 0;
    uint16_t ver = 0;
    if (!fio_rd(f, &ver, sizeof ver) || ver != IDX_VER) return 0;
    if (!fio_rd(f, &k->file_size, sizeof k->file_size) || !fio_rd(f, &k->file_mtime, sizeof k->file_mtime) ||
        !fio_rd(f, &k->font_mtime, sizeof k->font_mtime) || !fio_rd(f, &k->fs, sizeof k->fs) ||
        !fio_rd(f, &k->ls, sizeof k->ls) || !fio_rd(f, &k->cw, sizeof k->cw) ||
        !fio_rd(f, &k->ch, sizeof k->ch) || !fio_rd(f, &k->enc, sizeof k->enc) ||
        !fio_rd(f, k->font, sizeof k->font)) return 0;
    k->font[sizeof k->font - 1] = 0;
    return 1;
}
static int index_key_eq(const idx_key *a, const idx_key *b)
{
    return a->file_size == b->file_size && a->file_mtime == b->file_mtime &&
           a->font_mtime == b->font_mtime && a->fs == b->fs && a->ls == b->ls &&
           a->cw == b->cw && a->ch == b->ch && a->enc == b->enc &&
           strncmp(a->font, b->font, sizeof a->font) == 0;
}

/* 读缓存：头部与当前键一致则载入 (segs,pages) 并自检一致；返回 1=命中，0=未命中/损坏（调用方重排）。 */
static int index_cache_load(rd_book *b)
{
    char path[440];
    if (index_cache_path(b, path, sizeof path) != 0) return 0;
    FILE *f = fopen(path, "rb");
    if (!f) return 0;
    idx_key key, cur;
    int rc = 0;
    if (index_key_read(&key, f)) {
        index_key_fill(b, &cur);
        if (index_key_eq(&key, &cur)) {
            int32_t nsegs = 0, npages = 0;
            if (fio_rd(f, &nsegs, sizeof nsegs) && fio_rd(f, &npages, sizeof npages) &&
                nsegs >= 1 && npages >= 1 && nsegs <= 1000000 && npages <= 8000000 &&
                (uint64_t)npages <= cur.file_size + 1 && (uint64_t)nsegs <= cur.file_size + 1) {
                seg_t *segs = (seg_t *)malloc((size_t)nsegs * sizeof(seg_t));
                rd_book_page *pages = (rd_book_page *)malloc((size_t)npages * sizeof(rd_book_page));
                if (segs && pages &&
                    fio_rd(f, segs, (size_t)nsegs * sizeof(seg_t)) &&
                    fio_rd(f, pages, (size_t)npages * sizeof(rd_book_page))) {
                    /* 自检：page_count 求和 == npages 且 page_start 链正确；每页 seg 落在所属段区间。 */
                    int ok = 1, run = 0;
                    for (int32_t i = 0; i < nsegs && ok; i++) {
                        if (segs[i].page_count < 0 || segs[i].page_start != run) ok = 0;
                        else run += segs[i].page_count;
                    }
                    if (ok && run == npages) {
                        for (int32_t p = 0; p < npages && ok; p++) {
                            int32_t sg = pages[p].seg;
                            if (sg < 0 || sg >= nsegs || pages[p].seg_char < 0 ||
                                p < segs[sg].page_start || p >= segs[sg].page_start + segs[sg].page_count) ok = 0;
                        }
                    }
                    if (ok) {
                        b->segs = segs; b->pages = pages;
                        b->nsegs = (int)nsegs; b->npages = (int)npages;
                        rc = 1;                 /* 命中：调用方免 build_index */
                    } else { free(segs); free(pages); }
                } else { free(segs); free(pages); }
            }
        }
    }
    fclose(f);
    return rc;
}

/* 写缓存：先写 .tmp 再 rename（原子替换）；失败静默（下次重排）。 */
static void index_cache_save(rd_book *b)
{
    char path[440];
    if (b->nsegs <= 0 || b->npages <= 0) return;   /* 空书无页表可缓存 */
    if (index_cache_path(b, path, sizeof path) != 0) return;
    /* 目录由 reader.c 在 set_index_dir 前建好；这里 fopen 失败（无目录/只读）→ 静默跳过（下次重排）。 */
    char tmp[480];
    if (snprintf(tmp, sizeof tmp, "%s.tmp", path) >= (int)sizeof tmp) return;
    FILE *f = fopen(tmp, "wb");
    if (!f) return;
    idx_key key;
    int ok = 1;
    index_key_fill(b, &key);
    ok = ok && index_key_write(&key, f);
    ok = ok && fio_wr(f, &b->nsegs, sizeof b->nsegs) && fio_wr(f, &b->npages, sizeof b->npages);
    if (ok && b->nsegs > 0) ok = fio_wr(f, b->segs, (size_t)b->nsegs * sizeof(seg_t));
    if (ok && b->npages > 0) ok = fio_wr(f, b->pages, (size_t)b->npages * sizeof(rd_book_page));
    fclose(f);
    if (ok) { rename(tmp, path); } else { remove(tmp); }
}

/* ---- 文本：建索引（逐段 layout） ---- */
static int build_index(rd_book *b)
{
    rd_src_reset(b->src);
    size_t cap_segs = 64, cap_pages = 1024;
    b->segs = (seg_t *)malloc(cap_segs * sizeof(seg_t));
    b->pages = (rd_book_page *)malloc(cap_pages * sizeof(rd_book_page));
    if (!b->segs || !b->pages) return -6;
    b->nsegs = b->npages = 0;

    uint8_t *utf8 = (uint8_t *)malloc(RDTXT_SEG_UTF8_MAX + 8);
    if (!utf8) return -6;

    int seg_idx = 0;
    size_t ulen = 0;
    while (rd_src_next(b->src, utf8, RDTXT_SEG_UTF8_MAX + 8, &ulen) == 0) {
        if (seg_idx >= (int)cap_segs) { cap_segs *= 2; b->segs = (seg_t *)realloc(b->segs, cap_segs * sizeof(seg_t)); }
        uint32_t *cps = NULL; size_t n = 0;
        rd_utf8_to_cp(utf8, ulen, &cps, &n);
        rd_layout_in in;
        rd_layout_out out;
        rd_line *lines = (rd_line *)malloc((n ? n : 1) * sizeof(rd_line));
        rd_page *pages = (rd_page *)malloc((n ? n : 1) * sizeof(rd_page));
        if (!lines || !pages) { free(lines); free(pages); free(cps); free(utf8); return -6; }
        in.chars = cps; in.n = (int32_t)n; in.fs = b->fs; in.line_scale = b->ls;
        in.page_w = b->content_w; in.page_h = b->content_h; in.indent = b->fs;
        in.meas = book_meas; in.mctx = b;
        out.lines = lines; out.pages = pages; out.max_lines = (int)(n ? n : 1); out.max_pages = (int)(n ? n : 1);
        int lrc = rd_layout(&in, &out);
        free(cps);
        if (lrc != RD_LAYOUT_OK) { free(lines); free(pages); break; }
        b->segs[seg_idx].page_start = b->npages;
        b->segs[seg_idx].page_count = out.npages;
        for (int p = 0; p < out.npages; p++) {
            if (b->npages >= (int)cap_pages) { cap_pages *= 2; b->pages = (rd_book_page *)realloc(b->pages, cap_pages * sizeof(rd_book_page)); }
            b->pages[b->npages].seg = seg_idx;
            b->pages[b->npages].seg_char = out.pages[p].first_char;
            b->npages++;
        }
        free(lines); free(pages);
        seg_idx++;
    }
    free(utf8);
    b->nsegs = seg_idx;
    return 0;
}

/* ---- R3.2 分段流式（TXT）：把一段 UTF-8 布局并追加到 flat 页表 ---- */
static int append_seg_pages(rd_book *b, int seg_idx, const uint8_t *utf8, size_t ulen)
{
    uint32_t *cps = NULL; size_t n = 0;
    if (rd_utf8_to_cp(utf8, ulen, &cps, &n) != RD_ENC_OK) return -5;
    rd_line *lines = (rd_line *)malloc((n ? n : 1) * sizeof(rd_line));
    rd_page *pages = (rd_page *)malloc((n ? n : 1) * sizeof(rd_page));
    if (!lines || !pages) { free(lines); free(pages); free(cps); return -6; }
    rd_layout_in in;
    rd_layout_out out;
    in.chars = cps; in.n = (int32_t)n; in.fs = b->fs; in.line_scale = b->ls;
    in.page_w = b->content_w; in.page_h = b->content_h; in.indent = b->fs;
    in.meas = book_meas; in.mctx = b;
    out.lines = lines; out.pages = pages; out.max_lines = (int)(n ? n : 1); out.max_pages = (int)(n ? n : 1);
    int lrc = rd_layout(&in, &out);
    free(cps);
    if (lrc != RD_LAYOUT_OK) { free(lines); free(pages); return -4; }
    b->segs[seg_idx].page_start = b->npages;
    b->segs[seg_idx].page_count = out.npages;
    for (int p = 0; p < out.npages; p++) {
        if (b->npages >= b->pages_cap) {
            int nc = b->pages_cap ? b->pages_cap * 2 : 1024;
            rd_book_page *np = (rd_book_page *)realloc(b->pages, (size_t)nc * sizeof(rd_book_page));
            if (!np) { free(lines); free(pages); return -6; }
            b->pages = np; b->pages_cap = nc;
        }
        b->pages[b->npages].seg = seg_idx;
        b->pages[b->npages].seg_char = out.pages[p].first_char;
        b->npages++;
    }
    free(lines); free(pages);
    return 0;
}

/* ---- R3.2 段路径：把 [seg_built, upto_seg] 逐段（512KB 段文件 → utf8 → 布局）补齐进 flat 页表。
 * 幂等：已建段跳过。开书只建到目标（页 0/保存进度），翻页/跳转再按需补齐 —— 免整书一次性布局。 */
static int seg_ensure_built(rd_book *b, int upto_seg)
{
    if (!b->seg_dir[0] || b->fmt != RD_FMT_TXT) return 0;
    int total = b->seg_n > 0 ? b->seg_n : 1;
    if (upto_seg >= total) upto_seg = total - 1;
    if (upto_seg < 0) upto_seg = 0;
    int built_any = 0;
    while (b->seg_built <= upto_seg) {
        int idx = b->seg_built;
        size_t rawlen = 0;
        if (rdseg_rawlen(b->seg_dir, idx, &rawlen) != 0) break;
        if (b->segs_cap <= idx) {
            int nc = b->segs_cap ? b->segs_cap * 2 : 64;
            if (nc <= idx) nc = idx + 1;
            seg_t *ns = (seg_t *)realloc(b->segs, (size_t)nc * sizeof(seg_t));
            if (!ns) return -6;
            b->segs = ns; b->segs_cap = nc;
        }
        size_t cap = rawlen * 3 / 2 + 16;
        if (cap < RDTXT_SEG_UTF8_MAX + 8) cap = RDTXT_SEG_UTF8_MAX + 8;
        if (!b->seg_utf8 || b->seg_utf8_cap < cap) {
            uint8_t *t = (uint8_t *)malloc(cap);
            if (!t) return -6;
            free(b->seg_utf8); b->seg_utf8 = t; b->seg_utf8_cap = cap;
        }
        uint8_t *raw = (uint8_t *)malloc(rawlen ? rawlen : 1);
        if (!raw) return -6;
        size_t rn = 0;
        if (rdseg_load(b->seg_dir, idx, raw, rawlen, &rn) != 0) { free(raw); return -4; }
        size_t ulen = 0;
        int rc = rd_to_utf8(b->enc, raw, rn, b->seg_utf8, cap, &ulen);
        free(raw);
        if (rc == RD_ENC_ERR_BUFSZ) return -2;
        if (rc != RD_ENC_OK) return -3;
        int prc = append_seg_pages(b, idx, b->seg_utf8, ulen);
        if (prc != 0) return prc;
        b->seg_built++;
        built_any = 1;
    }
    b->nsegs = b->seg_built;
    if (built_any) index_cache_save(b);
    return 0;
}

/* ---- 正文重显 + 布局到复用缓冲 ---- */
static int load_seg(rd_book *b, int seg_idx)
{
    if (seg_idx == b->seg_cache_idx) return 0;
    size_t ulen = 0;
    if (b->seg_dir[0] && b->fmt == RD_FMT_TXT) {
        /* R3.2 段路径：只读当前页所在 512KB 段文件（有界，不全量读整书） */
        size_t rawlen = 0;
        if (rdseg_rawlen(b->seg_dir, seg_idx, &rawlen) != 0) return -4;
        size_t cap = rawlen * 3 / 2 + 16;
        if (cap < RDTXT_SEG_UTF8_MAX + 8) cap = RDTXT_SEG_UTF8_MAX + 8;
        if (!b->seg_utf8 || b->seg_utf8_cap < cap) {
            uint8_t *t = (uint8_t *)malloc(cap);
            if (!t) return -6;
            free(b->seg_utf8); b->seg_utf8 = t; b->seg_utf8_cap = cap;
        }
        uint8_t *raw = (uint8_t *)malloc(rawlen ? rawlen : 1);
        if (!raw) return -6;
        size_t rn = 0;
        int rc = rdseg_load(b->seg_dir, seg_idx, raw, rawlen, &rn);
        if (rc != 0) { free(raw); return -4; }
        int r2 = rd_to_utf8(b->enc, raw, rn, b->seg_utf8, cap, &ulen);
        free(raw);
        if (r2 == RD_ENC_ERR_BUFSZ) return -2;
        if (r2 != RD_ENC_OK) return -3;
    } else {
        size_t cap = RDTXT_SEG_UTF8_MAX + 8;
        if (!b->seg_utf8) b->seg_utf8 = (uint8_t *)malloc(cap);
        if (!b->seg_utf8) return -6;
        if (rd_src_seg(b->src, seg_idx, b->seg_utf8, cap, &ulen) != 0) return -4;
    }
    size_t n = 0;
    free(b->seg_cps); b->seg_cps = NULL;
    if (rd_utf8_to_cp(b->seg_utf8, ulen, &b->seg_cps, &n) != RD_ENC_OK) return -5;
    b->seg_cps_n = n;
    if (b->seg_lines) free(b->seg_lines);
    if (b->seg_pages) free(b->seg_pages);
    b->seg_lines = (rd_line *)malloc((n ? n : 1) * sizeof(rd_line));
    b->seg_pages = (rd_page *)malloc((n ? n : 1) * sizeof(rd_page));
    if (!b->seg_lines || !b->seg_pages) return -6;
    rd_layout_in in;
    rd_layout_out out;
    in.chars = b->seg_cps; in.n = (int32_t)n; in.fs = b->fs; in.line_scale = b->ls;
    in.page_w = b->content_w; in.page_h = b->content_h; in.indent = b->fs;
    in.meas = book_meas; in.mctx = b;
    out.lines = b->seg_lines; out.pages = b->seg_pages; out.max_lines = (int)(n ? n : 1); out.max_pages = (int)(n ? n : 1);
    int lrc = rd_layout(&in, &out);
    if (lrc != RD_LAYOUT_OK) { b->seg_nlines = b->seg_npages = 0; b->seg_cache_idx = -1; return -4; }
    b->seg_nlines = out.nlines; b->seg_npages = out.npages;
    b->seg_cache_idx = seg_idx;
    return 0;
}

int rd_book_open(rd_book **b, const char *path, const char *font_path,
                 int fs, int ls, int pw, int ph, int mx, int my, int top)
{
    if (!b || !path) return -1;
    rd_book *x = (rd_book *)calloc(1, sizeof *x);
    if (!x) return -6;
    if (strlen(path) >= sizeof x->path) { free(x); return -2; }
    strcpy(x->path, path);
    if (font_path) { if (strlen(font_path) >= sizeof x->font) { free(x); return -2; } strcpy(x->font, font_path); }
    const char *sl = strrchr(path, '/');
    strncpy(x->base, sl ? sl + 1 : path, sizeof x->base - 1); x->base[sizeof x->base - 1] = 0;
    char *dot = strrchr(x->base, '.'); if (dot) *dot = 0;

    if (fs <= 0) fs = 20;
    if (ls <= 0) ls = 130;
    x->fs = fs; x->ls = ls; x->pw = pw; x->ph = ph; x->mx = mx; x->my = my; x->top = top;
    x->content_w = pw - 2 * mx;
    x->content_h = ph - top - my;
    if (x->content_w < 10 || x->content_h < 10) { goto close; }

    if (rd_src_open(&x->src, path) != 0) goto close;
    x->fmt = rd_src_fmt(x->src);
    x->enc = RD_ENC_UTF8;
    rd_enc_t tmp_enc = RD_ENC_UTF8;
    if (rd_src_txt_enc(x->src, &tmp_enc) == 0) x->enc = tmp_enc;
    x->encname = fmt_encname(x->fmt, x->enc);
    x->is_img = (x->fmt == RD_FMT_CBZ);

    if (!x->is_img) {
        if (rdft_init(&x->ft) != 0) goto close;
        if (font_path && rdft_load_font(x->ft, x->font) != 0) { rdft_free(x->ft); x->ft = NULL; goto close; }
        if (x->ft) rdft_set_px(x->ft, fs);
        x->seg_cache_idx = -1;
        int seg_mode = 0;
        /* R3.2 分段流式（TXT 且段 base 已配置）：开书切 512KB 段文件，逐段按需布局（不全量）。 */
        if (g_seg_base[0] && x->fmt == RD_FMT_TXT) {
            char sdir[600];
            if (rdseg_dir_for(x->path, sdir, sizeof sdir) == 0) {
                strncpy(x->seg_dir, sdir, sizeof x->seg_dir - 1); x->seg_dir[sizeof x->seg_dir - 1] = 0;
                int ns = rdseg_build(x->path, x->enc, x->seg_dir);
                if (ns > 0) { x->seg_n = ns; seg_mode = 1; }
            }
        }
        if (seg_mode) {
            /* 命中缓存（书+版面+编码+字体未变）→ 载入已建 (segs,pages)；否则仅布局段 0 起步，
             * 翻页/跳转再 seg_ensure_built 补齐（治大书开书整表布局卡 UI 线程）。 */
            x->segs = NULL; x->pages = NULL; x->nsegs = x->npages = 0;
            x->seg_built = 0; x->segs_cap = x->pages_cap = 0;
            if (index_cache_load(x) != 1) {
                if (seg_ensure_built(x, 0) != 0) goto close;
            }
            if (x->nsegs < 1) {                     /* 段 0 空（理论）→ 兜底再建 */
                if (seg_ensure_built(x, 0) != 0) goto close;
            }
            x->segs_cap = x->nsegs; x->pages_cap = x->npages;
            x->seg_built = x->nsegs;                /* 缓存命中时恢复到已建段数 */
        } else {
            /* 页索引缓存命中（书+字号+版面+编码+字体未变）→ 免整书重排，秒开；未命中 → 重排并落盘。 */
            if (index_cache_load(x) != 1) {
                if (build_index(x) != 0) goto close;
                index_cache_save(x);
            }
        }
    } else {
        int pages = rd_src_pages(x->src);
        x->npages = pages > 0 ? pages : 0;
    }
    x->cur = 0;
    *b = x;
    return 0;
close:
    rd_book_close(x);
    return -1;
}

void rd_book_close(rd_book *b)
{
    if (!b) return;
    free(b->segs);
    free(b->pages);
    free(b->seg_utf8);
    free(b->seg_cps);
    free(b->seg_lines);
    free(b->seg_pages);
    if (b->ft) rdft_free(b->ft);
    if (b->src) rd_src_free(b->src);
    free(b);
}

int rd_book_pages(rd_book *b) { return b ? b->npages : 0; }
int rd_book_current(rd_book *b) { return b ? b->cur : 0; }
int rd_book_font(rd_book *b)   { return b ? b->fs : 0; }
int rd_book_ls(rd_book *b)     { return b ? b->ls : 0; }
int rd_book_is_image(rd_book *b) { return b ? b->is_img : 0; }
const char *rd_book_encname(const rd_book *b) { return b ? (b->encname ? b->encname : "") : ""; }
rd_enc_t    rd_book_enc_get(const rd_book *b)  { return b ? b->enc : RD_ENC_UTF8; }

void rd_book_geom(rd_book *b, int *fs, int *ls, int *pw, int *ph, int *mx, int *my, int *top)
{
    if (!b) return;
    if (fs) *fs = b->fs;
    if (ls) *ls = b->ls;
    if (pw) *pw = b->pw;
    if (ph) *ph = b->ph;
    if (mx) *mx = b->mx;
    if (my) *my = b->my;
    if (top) *top = b->top;
}
const char *rd_book_basename(const rd_book *b) { return b ? b->base : ""; }
const char *rd_book_path(const rd_book *b)     { return b ? b->path : ""; }

/* R3：TXT 编码切换——重开 src（带覆盖编码）、重建页索引、回锚当前页。非 TXT/CBZ 返回 -1。
 * 事务式：先开新 src 成功才换（失败保留旧 src，书仍可用，返回负值）。 */
int rd_book_set_enc(rd_book *b, rd_enc_t enc)
{
    if (!b || b->is_img || b->fmt != RD_FMT_TXT) return -1;
    if (enc == b->enc) return b->cur;   /* 同编码，无需重建 */
    int seg; int32_t ch;
    rd_book_anchor(b, &seg, &ch);

    rd_enc_t oldenc = b->enc;
    rd_src *ns = NULL;
    if (rd_src_open_with_enc(&ns, b->path, &enc) != 0) return -2;   /* 旧 src 未动 */
    rd_src_free(b->src); b->src = ns;                               /* 换新 */
    b->enc = enc;
    b->encname = fmt_encname(b->fmt, b->enc);

    /* 重建索引（复用现值 fs/ls/content_*），再回锚 */
    free(b->segs); free(b->pages); b->segs = NULL; b->pages = NULL;
    b->nsegs = b->npages = 0; b->seg_built = 0; b->segs_cap = b->pages_cap = 0;
    if (b->seg_dir[0]) {
        /* R3.2 段路径：编码变了 → 段文件边界/解码不同 → 重建段文件 + 按需布局（段 0 起步） */
        if (oldenc != b->enc) rdseg_clear(b->seg_dir);
        b->seg_n = rdseg_build(b->path, b->enc, b->seg_dir);
        if (seg_ensure_built(b, 0) != 0) return -3;
        index_cache_save(b);
    } else {
        if (build_index(b) != 0) return -3;   /* 新 src 有效但索引空 → 渲染返回 -1，安全降级 */
        index_cache_save(b);                  /* 编码切换后重新落盘（键含 enc，与旧缓存并存不冲突） */
    }
    return rd_book_jump_to_anchor(b, seg, ch, b->fs, b->ls);
}

void rd_book_anchor(rd_book *b, int *seg, int32_t *ch)
{
    if (!b || b->npages <= 0) { if (seg) *seg = 0; if (ch) *ch = 0; return; }
    int p = b->cur < 0 ? 0 : (b->cur >= b->npages ? b->npages - 1 : b->cur);
    if (seg) *seg = b->pages[p].seg;
    if (ch) *ch = b->pages[p].seg_char;
}

int rd_book_turn(rd_book *b, int delta)
{
    if (!b || b->npages <= 0) return 0;
    int np = b->cur + delta;
    if (np < 0) np = 0;
    /* R3.2 段路径：翻到已建表尾之外 → 按需补下一段（一次翻页只补到够用，不全量） */
    if (b->seg_dir[0] && b->fmt == RD_FMT_TXT && np >= b->npages && b->seg_built < b->seg_n) {
        while (np >= b->npages && b->seg_built < b->seg_n) {
            if (seg_ensure_built(b, b->seg_built) != 0) break;
        }
    }
    if (np >= b->npages) np = b->npages - 1;
    b->cur = np;
    return np;
}

int rd_book_set_page(rd_book *b, int page)
{
    if (!b || b->npages <= 0) return 0;
    /* R3.2 段路径：跳到已建表外 → 按需补段到目标页（跳到哪建到哪） */
    if (b->seg_dir[0] && b->fmt == RD_FMT_TXT && page >= b->npages && b->seg_built < b->seg_n) {
        while (page >= b->npages && b->seg_built < b->seg_n) {
            if (seg_ensure_built(b, b->seg_built) != 0) break;
        }
    }
    if (page < 0) page = 0;
    if (page >= b->npages) page = b->npages - 1;
    b->cur = page;
    return page;
}

/* ---- 文本页渲染（FreeType 字形 → 全屏 565） ---- */
static int render_text_page(rd_book *b, int page_no, uint16_t *out, int pitch, uint16_t bg565, uint16_t fg565)
{
    int npix = b->pw * b->ph;
    for (int i = 0; i < npix; i++) out[i] = bg565;
    rd_book_page *pg = &b->pages[page_no];
    int seg_idx = (int)pg->seg;
    if (seg_idx < 0 || seg_idx >= b->nsegs) return -1;
    if (load_seg(b, seg_idx) != 0) return -2;
    int local_page = page_no - b->segs[seg_idx].page_start;
    if (local_page < 0 || local_page >= b->seg_npages) return 1;
    rd_page *pp = &b->seg_pages[local_page];
    int asc = rdft_ascender(b->ft);
    int screen_x0 = b->mx;
    int screen_y0 = b->top;
    for (int li = 0; li < pp->nlines; li++) {
        rd_line *ln = &b->seg_lines[pp->first_line + li];
        int pen = screen_x0 + ln->x;
        int baseline = screen_y0 + ln->y + asc;
        for (int32_t ci = ln->s; ci < ln->e; ci++) {
            uint32_t cp = b->seg_cps[ci];
            int adv = 0, bw = 0, bh = 0, left = 0, btop = 0;
            const uint8_t *bmp = NULL;
            rdft_glyph(b->ft, cp, &adv, &bmp, &bw, &bh, &left, &btop);
            if (bmp && bw > 0)
                rdft_blend565(out, pitch, b->pw, b->ph, pen, baseline, bmp, bw, bh, left, btop, fg565, bg565);
            pen += adv;
        }
    }
    return 0;
}

/* ---- CBZ 图片页渲染（rdimg 解码+降采样 → 内容区居中） ---- */
static int render_img_page(rd_book *b, int page_no, uint16_t *out, int pitch, uint16_t bg565)
{
    int npix = b->pw * b->ph;
    for (int i = 0; i < npix; i++) out[i] = bg565;
    uint8_t *data = NULL; size_t size = 0;
    if (rd_src_page(b->src, page_no, &data, &size) != 0) return -1;
    uint16_t *scaled = NULL; int sw = 0, sh = 0;
    if (rdimg_decode_scale(data, size, b->content_w, b->content_h, &scaled, &sw, &sh) != 0) {
        free(data); return -2;
    }
    int x0 = b->mx + (b->content_w - sw) / 2;
    int y0 = b->top + (b->content_h - sh) / 2;
    int pitch_px = pitch / 2;
    for (int y = 0; y < sh; y++) {
        int ty = y0 + y; if (ty < 0 || ty >= b->ph) continue;
        for (int x = 0; x < sw; x++) {
            int tx = x0 + x; if (tx < 0 || tx >= b->pw) continue;
            out[(size_t)ty * pitch_px + tx] = scaled[(size_t)y * sw + x];
        }
    }
    free(scaled);
    free(data);
    return 0;
}

int rd_book_render(rd_book *b, int page_no, uint16_t *out, int pitch, uint16_t bg565, uint16_t fg565)
{
    if (!b || !out || b->npages <= 0 || page_no < 0 || page_no >= b->npages) return -1;
    if (b->is_img) return render_img_page(b, page_no, out, pitch, bg565);
    return render_text_page(b, page_no, out, pitch, bg565, fg565);
}

/* ---- 重排 + 回锚 ---- */
int rd_book_set_size(rd_book *b, int fs, int ls)
{
    if (!b) return -1;
    if (b->is_img) { b->fs = fs; b->ls = ls; return 0; }
    if (fs <= 0) fs = b->fs;
    if (ls <= 0) ls = b->ls;
    int anchor_seg, anchor_ch;
    rd_book_anchor(b, &anchor_seg, &anchor_ch);
    return rd_book_jump_to_anchor(b, anchor_seg, anchor_ch, fs, ls);
}

int rd_book_jump_to_anchor(rd_book *b, int seg, int32_t ch, int fs, int ls)
{
    if (!b) return -1;
    if (b->is_img) {
        if (seg >= 0 && seg < b->npages) b->cur = seg;
        return b->cur;
    }
    if (fs != b->fs || ls != b->ls) {
        b->fs = fs; b->ls = ls;
        b->content_w = b->pw - 2 * b->mx;
        b->content_h = b->ph - b->top - b->my;
        if (b->ft) rdft_set_px(b->ft, fs);
        seg_t *nos = b->segs; int n_oldsegs = b->nsegs;
        rd_book_page *nop = b->pages; int n_oldpages = b->npages;
        b->segs = NULL; b->pages = NULL; b->nsegs = b->npages = 0;
        if (b->seg_dir[0] && b->fmt == RD_FMT_TXT) {
            /* R3.2 段路径：只重布局到含锚的段（不全量；段文件不变，仅页表变） */
            b->seg_built = 0; b->segs_cap = b->pages_cap = 0;
            if (seg_ensure_built(b, seg) != 0) { b->segs = nos; b->pages = nop; b->nsegs = n_oldsegs; b->npages = n_oldpages; return -5; }
            free(nos); free(nop);
            index_cache_save(b);
        } else {
            if (build_index(b) != 0) { b->segs = nos; b->pages = nop; b->nsegs = n_oldsegs; b->npages = n_oldpages; return -5; }
            free(nos); free(nop);
            index_cache_save(b);              /* 字号/行距改变后重新落盘（键含 fs/ls） */
        }
    } else if (b->seg_dir[0] && b->fmt == RD_FMT_TXT && seg >= b->seg_built) {
        /* 锚在未建段 → 按需补齐（重开续读/目录跳转到后部） */
        if (seg_ensure_built(b, seg) != 0) return -5;
    }
    int target = 0;
    for (int p = 0; p < b->npages; p++) {
        int ps = b->pages[p].seg;
        if (ps < seg) { target = p + 1; continue; }
        if (ps > seg) break;
        if (b->pages[p].seg_char >= ch) { target = p; break; }
        target = p;
    }
    if (target >= b->npages) target = b->npages - 1;
    if (target < 0) target = 0;
    b->cur = target;
    return target;
}

/* ---- SDK 字库兜底（文本格式） ---- */
int rd_book_render_text(rd_book *b, int page_no, rd_book_line_fn fn, void *ctx)
{
    if (!b || !fn || b->is_img || b->npages <= 0 || page_no < 0 || page_no >= b->npages) return -1;
    rd_book_page *pg = &b->pages[page_no];
    int seg_idx = (int)pg->seg;
    if (seg_idx < 0 || seg_idx >= b->nsegs) return -1;
    if (load_seg(b, seg_idx) != 0) return -2;
    int local_page = page_no - b->segs[seg_idx].page_start;
    if (local_page < 0 || local_page >= b->seg_npages) return 1;
    rd_page *pp = &b->seg_pages[local_page];
    uint8_t *line_utf8 = (uint8_t *)malloc((size_t)(b->content_w * 4 + 32));
    if (!line_utf8) return -6;
    for (int li = 0; li < pp->nlines; li++) {
        rd_line *ln = &b->seg_lines[pp->first_line + li];
        int x = b->mx + ln->x, y = b->top + ln->y;
        size_t o = 0;
        for (int32_t ci = ln->s; ci < ln->e; ci++) {
            uint8_t tmp[4];
            int n = rd_cp_to_utf8(b->seg_cps[ci], tmp);
            memcpy(line_utf8 + o, tmp, (size_t)n); o += (size_t)n;
        }
        line_utf8[o] = 0;
        fn(x, y, (const char *)line_utf8, (int)o, ctx);
    }
    free(line_utf8);
    return 0;
}

/* ---- 目录（转 rd_src） ---- */
int rd_book_toc_n(const rd_book *b)
{
    return (b && b->src && !b->is_img) ? rd_src_toc_n(b->src) : 0;
}
int rd_book_toc(const rd_book *b, int i, char *title, int tsz, int *seg, int32_t *ch)
{
    if (!b || !b->src || b->is_img || !title) return -1;
    rd_toc_entry t;
    if (rd_src_toc(b->src, i, &t) != 0) return -1;
    strncpy(title, t.title, (size_t)tsz - 1); title[tsz - 1] = 0;
    if (seg) *seg = t.seg;
    if (ch) *ch = t.ch;
    return 0;
}