/* 内存扫描：找进程里已经解密成明文的 class 字节。
 *
 * 为什么走这条路：实测 Frida 的内联挂钩（Interceptor.attach 到 JVM_DefineClass*）
 * 会让这套运行时直接 SIGSEGV，attach 又太晚（类早加载完了）。
 * 扫描内存不改任何代码，风险最低。
 */

#include <mach/mach.h>
#include <mach/vm_region.h>
#include <pthread.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>

#define SCAN_LOG "/tmp/spine-viewpanel.log"
#define SCAN_DIR "/tmp/spine-classes/scan"

static void scan_log(const char *message) {
    FILE *file = fopen(SCAN_LOG, "a");
    if (file) { fprintf(file, "%s\n", message); fclose(file); }
}

/* 用常量池长度算出一个 class 文件到底多少字节；不是合法 class 就返回 -1。 */
static int class_file_length(const unsigned char *p, size_t avail) {
    if (avail < 10) return -1;
    if (!(p[0] == 0xCA && p[1] == 0xFE && p[2] == 0xBA && p[3] == 0xBE)) return -1;
    uint16_t cp_count = (uint16_t)((p[8] << 8) | p[9]);
    size_t i = 10;
    for (uint16_t index = 1; index < cp_count; index++) {
        if (i >= avail) return -1;
        uint8_t tag = p[i++];
        switch (tag) {
            case 1: {
                if (i + 2 > avail) return -1;
                uint16_t len = (uint16_t)((p[i] << 8) | p[i + 1]);
                i += 2 + len;
                break;
            }
            case 3: case 4: i += 4; break;
            case 5: case 6: i += 8; index++; break;
            case 7: case 8: case 16: case 19: case 20: i += 2; break;
            case 9: case 10: case 11: case 12: case 17: case 18: i += 4; break;
            case 15: i += 3; break;
            default: return -1;
        }
        if (i > avail) return -1;
    }
    if (i + 8 > avail) return -1;
    uint16_t interfaces = (uint16_t)((p[i + 6] << 8) | p[i + 7]);
    i += 8 + (size_t)interfaces * 2;
    for (int section = 0; section < 3; section++) {
        if (i + 2 > avail) return -1;
        uint16_t count = (uint16_t)((p[i] << 8) | p[i + 1]);
        i += 2;
        for (uint16_t k = 0; k < count; k++) {
            if (i + 8 > avail) return -1;
            uint16_t attributes = (uint16_t)((p[i + 6] << 8) | p[i + 7]);
            i += 8;
            for (uint16_t a = 0; a < attributes; a++) {
                if (i + 6 > avail) return -1;
                uint32_t len = ((uint32_t)p[i + 2] << 24) | ((uint32_t)p[i + 3] << 16)
                             | ((uint32_t)p[i + 4] << 8) | p[i + 5];
                i += 6 + len;
                if (i > avail) return -1;
            }
        }
    }
    return (int)i;
}

static void scan_memory(void) {
    mkdir("/tmp/spine-classes", 0755);
    mkdir(SCAN_DIR, 0755);

    int dumped = 0;
    uint64_t scanned = 0;
    vm_address_t address = 0;
    while (dumped < 6000) {
        vm_size_t size = 0;
        vm_region_basic_info_data_64_t info;
        mach_msg_type_number_t count = VM_REGION_BASIC_INFO_COUNT_64;
        mach_port_t object = MACH_PORT_NULL;
        kern_return_t kr = vm_region_64(mach_task_self(), &address, &size, VM_REGION_BASIC_INFO_64,
                                        (vm_region_info_t)&info, &count, &object);
        if (kr != KERN_SUCCESS) break;
        int readable = (info.protection & VM_PROT_READ) != 0;
        /* 只扫进程自己分配的区域，跳过文件映射和共享缓存，减少误报与耗时。 */
        int is_shared = info.shared;
        if (readable && !is_shared && size >= 4096 && size <= (vm_size_t)256 * 1024 * 1024) {
            const unsigned char *base = (const unsigned char *)address;
            const unsigned char *end = base + size;
            scanned += size;
            for (const unsigned char *p = base; p + 4 < end; p++) {
                if (p[0] != 0xCA || p[1] != 0xFE || p[2] != 0xBA || p[3] != 0xBE) continue;
                int length = class_file_length(p, (size_t)(end - p));
                if (length < 100 || length > 4 * 1024 * 1024) continue;
                char path[256];
                snprintf(path, sizeof(path), SCAN_DIR "/mem_%05d.class", dumped);
                FILE *file = fopen(path, "wb");
                if (file) {
                    fwrite(p, 1, (size_t)length, file);
                    fclose(file);
                    dumped++;
                }
                if (dumped >= 6000) break;
            }
        }
        address += size;
    }
    char message[256];
    snprintf(message, sizeof(message), "内存扫描：扫了 %.0f MB，dump 出 %d 个 class",
             (double)scanned / 1048576.0, dumped);
    scan_log(message);
}

static void *scan_thread(void *unused) {
    (void)unused;
    sleep(20);
    scan_memory();
    return NULL;
}

__attribute__((constructor))
static void scan_install(void) {
    const char *enable = getenv("SPINE_VIEWPANEL_DUMP");
    if (!enable || enable[0] != '1') return;
    scan_log("=== memscan.dylib 已载入，20 秒后开始扫描 ===");
    pthread_t thread;
    if (pthread_create(&thread, NULL, scan_thread, NULL) == 0) pthread_detach(thread);
}