/* ui/viewer.c — 文本预览页（ACT_VIEWER，子页）view + 控制器。
 *
 * 只读、可滚动、≤256KB 截断（APP_READ_MAX，超长只读前 256KB）。
 * 行模型：把读入内容按 '\n' 切成逻辑行（<= VIEWER_MAX_LINES，超长截断并附加提示）；
 * 每逻辑行按可视列宽软换行成「屏幕行」；滚动按屏幕行像素仿真化（只画可见屏幕行）。
 * 打开时 meow_view_page_push(ACT_VIEWER)（on_enter 置标题/清滚动/整帧重画）；返回=左缘左滑/返回钮。
 */
#include "files_internal.h"

#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

typedef struct { meow_view *view; int active; } viewer_ctrl;
static viewer_ctrl g_vc;

#define VIEWER_MAX_LINES  8192   /* 逻辑行上限（超长折行会很多，但按行数界内存） */

static char  *g_buf;         /* malloc'd 读入内容（前 256KB，NUL 结尾） */
static size_t g_buf_len;
static char   g_fname[FSX_MAX_NAME];
static int   *g_line;        /* g_nline 个：每逻辑行起始偏移 */
static int    g_nline;
static int   *g_rown;        /* g_nline 个：每逻辑行对应的首「屏幕行」下标 */
static int    g_nrows;       /* 总屏幕行数（= 末行 rown + 其折行数） */
static int    g_vscroll;     /* 滚动偏移（px） */
static int    g_vdrag, g_vdrag_last_y;

static meow_widget *g_tb;
static meow_widget *g_vcw;   /* 内容区 custom widget（画文本行） */
static app_rect_t   r_content;

/* 可视列宽（像素）。 */
static int viewer_colw(void) { return r_content.w - 2 * APP_PAD; }
/* 文本行区视口高（底部留页脚）。 */
static int viewer_vp_h(void) { return r_content.h - APP_FOOTER_H; }
/* 屏幕行高（px）。 */
static int viewer_rowh(const meow_theme *th) { return meow_ui_text_height(th->font_body) + 6; }

/* 折行：返回逻辑行 li 折成的屏幕行数；若 intra>=0，把该屏幕行文本写入 out（NUL 结尾）。 */
static int viewer_wrap_line(int li, int intra, char *out, int outsz)
{
    if (!g_buf || li < 0 || li >= g_nline) return 0;
    int start = g_line[li];
    int end   = (li + 1 < g_nline) ? g_line[li + 1] : (int)g_buf_len;
    int len   = end - start;
    while (len > 0 && (g_buf[start + len - 1] == '\n' || g_buf[start + len - 1] == '\r')) len--;
    int colw = viewer_colw();
    int col = 0, row = 0, outlen = 0;
    char ch[2]; ch[1] = '\0';
    for (int i = 0; i < len; i++) {
        ch[0] = g_buf[start + i];
        if (ch[0] == '\r') continue;
        int w = meow_ui_text_width(ch, 20);
        if (col + w > colw && col > 0) { row++; col = 0; }
        if (row == intra && out && outlen < outsz - 1) out[outlen++] = ch[0];
        col += w;
    }
    if (out) out[outlen] = '\0';
    return row + 1;
}

/* 读入文件并建行表；0=文本预览可读，-1=非文本/读失败。 */
static int viewer_build(const char *path)
{
    free(g_buf); free(g_line); free(g_rown);
    g_buf = NULL; g_line = NULL; g_rown = NULL;
    g_nline = 0; g_nrows = 0; g_buf_len = 0;
    g_fname[0] = '\0';

    int fd = open(path, O_RDONLY);
    if (fd < 0) return -1;
    size_t cap = APP_READ_MAX + 1;
    g_buf = (char *)malloc(cap);
    if (!g_buf) { close(fd); return -1; }
    ssize_t n = read(fd, g_buf, APP_READ_MAX);
    close(fd);
    if (n <= 0) { free(g_buf); g_buf = NULL; return -1; }
    g_buf_len = (size_t)n;
    g_buf[g_buf_len] = '\0';

    /* 非文本嗅探：前 512 字节出现 NUL 视为二进制 */
    int lim = (int)(g_buf_len < 512 ? g_buf_len : 512);
    for (int i = 0; i < lim; i++) if (g_buf[i] == '\0') { free(g_buf); g_buf = NULL; return -1; }

    /* 文件名 */
    const char *bn = fsx_basename(path);
    strncpy(g_fname, bn, FSX_MAX_NAME - 1);
    g_fname[FSX_MAX_NAME - 1] = '\0';

    /* 切逻辑行（上限 VIEWER_MAX_LINES；超出截断，末行吸收剩余 + 附截断提示） */
    int cap_l = VIEWER_MAX_LINES;
    g_line  = (int *)malloc((size_t)cap_l * sizeof(int));
    g_rown  = (int *)malloc((size_t)cap_l * sizeof(int));
    if (!g_line || !g_rown) { free(g_buf); free(g_line); free(g_rown); g_buf = NULL; g_line=NULL; g_rown=NULL; return -1; }
    g_nline = 0;
    g_line[g_nline++] = 0;
    int truncated = 0;
    for (size_t i = 0; i < g_buf_len; i++) {
        if (g_buf[i] == '\n') {
            if (g_nline < cap_l) g_line[g_nline++] = (int)i + 1;
            else { truncated = 1; break; }
        }
    }
    if (truncated) {
        g_line[g_nline - 1] = (int)g_buf_len;   /* 让最后一行吸收剩余 */
    }

    /* 折行累加 → 屏幕行下标 */
    g_nrows = 0;
    for (int li = 0; li < g_nline; li++) {
        g_rown[li] = g_nrows;
        g_nrows += viewer_wrap_line(li, -1, NULL, 0);
    }

    return 0;
}

/* 宿主测试/入口兼容：读入 buffer 并解析行。 */
void viewer_load(const char *path) { viewer_build(path); }

/* 内容区 render_cb：虚拟化画可见屏幕行。 */
static void viewer_render(meow_widget *w, const meow_theme *th, void *ctx)
{
    (void)w; (void)ctx;
    if (!g_buf || g_nrows <= 0) {
        app_draw_empty(r_content, "NOT A TEXT FILE", g_fname[0] ? g_fname : "");
        return;
    }
    int rowh = viewer_rowh(th);
    if (rowh < 1) rowh = 1;
    int vp = viewer_vp_h();
    int top = g_vscroll / rowh;
    int bot = (g_vscroll + vp) / rowh + 1;
    if (top < 0) top = 0;
    if (bot > g_nrows) bot = g_nrows;

    char row[512];
    for (int sr = top; sr < bot; sr++) {
        /* 二分找逻辑行 li：g_rown[li] <= sr 的最大 li */
        int lo = 0, hi = g_nline - 1, li = 0;
        while (lo <= hi) {
            int mid = (lo + hi) / 2;
            if (g_rown[mid] <= sr) { li = mid; lo = mid + 1; }
            else                   { hi = mid - 1; }
        }
        int intra = sr - g_rown[li];
        row[0] = '\0';
        viewer_wrap_line(li, intra, row, (int)sizeof row);
        if (!row[0] && intra == 0) row[0] = ' ', row[1] = '\0';
        int ry = r_content.y + (sr * rowh - g_vscroll);
        if (ry < r_content.y) continue;
        if (ry >= r_content.y + vp) break;
        meow_ui_text(r_content.x + APP_PAD, ry, row, th->font_body, th->onSurface);
    }
    /* 页脚：行数 + 文件名（含截断提示） */
    char foot[128];
    if (g_buf_len >= APP_READ_MAX)
        snprintf(foot, sizeof foot, ">256KB (truncated)   %d row(s)", g_nrows);
    else
        snprintf(foot, sizeof foot, "%d row(s)", g_nrows);
    app_draw_footer(r_content, foot);
}

static int viewer_hit(meow_widget *w, int x, int y, void *ctx)
{
    (void)w; (void)ctx;
    return x >= r_content.x && x < r_content.x + r_content.w &&
           y >= r_content.y && y < r_content.y + r_content.h;
}

static void viewer_clamp_scroll(void)
{
    const meow_theme *th = meow_theme_get();
    int rowh = viewer_rowh(th);
    int content_h = g_nrows * rowh;
    int maxs = content_h - viewer_vp_h();
    if (maxs < 0) maxs = 0;
    if (g_vscroll < 0) g_vscroll = 0;
    if (g_vscroll > maxs) g_vscroll = maxs;
}

int viewer_open_file(const char *path)
{
    if (viewer_build(path) != 0) return -1;
    meow_view_page_push(ACT_VIEWER);
    return 0;
}

int viewer_is_active(void) { return g_vc.active; }

void viewer_swipe(int dir, int dist)
{
    if (dir != MEOW_SWIPE_UP && dir != MEOW_SWIPE_DOWN) return;
    int del = (dir == MEOW_SWIPE_UP) ? dist : -dist;
    g_vscroll += del;
    viewer_clamp_scroll();
    meow_ui_invalidate(r_content.x, r_content.y, r_content.w, r_content.h);
}

void viewer_touch_down(int x, int y)
{
    (void)x;
    g_vdrag = 0; g_vdrag_last_y = 0;
    if (!g_buf) return;
    if (meow_widget_hit(g_vcw, x, y)) { g_vdrag = 1; g_vdrag_last_y = y; }
}

void viewer_touch_move(int x, int y)
{
    (void)x;
    if (!g_vdrag) return;
    int dy = y - g_vdrag_last_y;
    g_vdrag_last_y = y;
    if (dy == 0) return;
    g_vscroll -= dy;
    viewer_clamp_scroll();
    meow_ui_invalidate(r_content.x, r_content.y, r_content.w, r_content.h);
}

int viewer_on_tap(int x, int y)
{
    if (g_tb) {
        int ah = meow_topappbar_hit(g_tb, x, y);
        if (ah == MEOW_TOPBAR_BACK) { meow_view_page_pop(); return 1; }
    }
    return 0;
}

/* ---- 页 view 生命周期 ---- */

static void viewer_page_create(meow_view *v, void *ctx)
{
    (void)v;
    ((viewer_ctrl *)ctx)->view = v;
    r_content = app_content_rect();
    meow_ui_activity_push(ACT_VIEWER);       /* 让下面控件 owner=ACT_VIEWER */
    g_tb = app_topbar_create("Preview", 1, NULL);
    g_vcw = meow_widget_custom_create(r_content.x, r_content.y, r_content.w, r_content.h,
                                      viewer_render, viewer_hit, NULL);
    meow_ui_activity_pop();
}

static void viewer_page_enter(meow_view *v, void *ctx)
{
    (void)v;
    ((viewer_ctrl *)ctx)->active = 1;
    g_vscroll = 0;
    if (g_tb) meow_topappbar_set_title(g_tb, g_fname[0] ? g_fname : "Preview");
    const meow_theme *th = meow_theme_get();
    meow_ui_set_page_bg(th->bg);
    meow_ui_paint_full();
}

static void viewer_page_leave(meow_view *v, void *ctx)
{
    (void)v;
    ((viewer_ctrl *)ctx)->active = 0;
}

static void viewer_page_destroy(meow_view *v, void *ctx)
{
    (void)v; (void)ctx;
    if (g_vcw) { meow_widget_free(g_vcw); g_vcw = NULL; }
    if (g_tb) { meow_widget_free(g_tb); g_tb = NULL; }
    free(g_buf); free(g_line); free(g_rown);
    g_buf = NULL; g_line = NULL; g_rown = NULL;
}

meow_view *viewer_view_create(void)
{
    static const meow_view_hooks h = {
        .on_create  = viewer_page_create,
        .on_enter   = viewer_page_enter,
        .on_leave   = viewer_page_leave,
        .on_destroy = viewer_page_destroy,
    };
    return meow_view_create(ACT_VIEWER, MEOW_VIEW_ACTIVITY, &h, &g_vc);
}