kidsbox/device/main/CacheManager.cpp

#include "CacheManager.hpp"

#include <esp_log.h>
#include <esp_http_client.h>
#include <freertos/FreeRTOS.h>
#include <freertos/task.h>
#include <sys/stat.h>
#include <dirent.h>
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <string>
#include <functional>

static const char* TAG = "CacheManager";

struct DownloadArgs {
    std::string url;
    std::function<void(bool)> onComplete;
};

CacheManager::CacheManager() {
    mkdir(CACHE_DIR, 0777);
}

/* djb2 hash of the URL, returned as 8-char hex string */
std::string CacheManager::urlToKey(const std::string& url) const {
    uint32_t hash = 5381;
    for(char c : url) {
        hash = ((hash << 5) + hash) ^ (uint8_t)c;
    }
    char buf[9];
    snprintf(buf, sizeof(buf), "%08lx", (unsigned long)hash);
    return std::string(buf);
}

std::string CacheManager::urlExtension(const std::string& url) const {
    /* Strip query/fragment before looking for extension */
    size_t qs = url.find('?');
    std::string path = (qs != std::string::npos) ? url.substr(0, qs) : url;

    size_t dot = path.rfind('.');
    size_t slash = path.rfind('/');

    if(dot != std::string::npos && (slash == std::string::npos || dot > slash)) {
        std::string ext = path.substr(dot); /* includes the dot */
        if(ext.size() <= 5) return ext;     /* ignore suspiciously long "extensions" */
    }
    return ".mp3"; /* sensible default */
}

std::string CacheManager::keyToPath(const std::string& key, const std::string& ext) const {
    return std::string(CACHE_DIR) + "/" + key + ext;
}

/* Find any file in CACHE_DIR whose name starts with key */
std::string CacheManager::findFileByKey(const std::string& key) const {
    DIR* dir = opendir(CACHE_DIR);
    if(!dir) return "";

    struct dirent* entry;
    while((entry = readdir(dir)) != NULL) {
        std::string name(entry->d_name);
        if(name.rfind(key, 0) == 0) {
            closedir(dir);
            return std::string(CACHE_DIR) + "/" + name;
        }
    }
    closedir(dir);
    return "";
}

std::string CacheManager::getCachedPath(const std::string& url) const {
    if(url.empty()) return "";
    std::string key  = urlToKey(url);
    std::string path = findFileByKey(key);
    if(!path.empty()) {
        ESP_LOGI(TAG, "Cache hit: %s -> %s", url.c_str(), path.c_str());
    }
    return path;
}

void CacheManager::downloadTask(void* arg) {
    auto* dl = static_cast<DownloadArgs*>(arg);

    ESP_LOGI(TAG, "Downloading: %s", dl->url.c_str());

    CacheManager cm;
    std::string key  = cm.urlToKey(dl->url);
    std::string ext  = cm.urlExtension(dl->url);
    std::string path = cm.keyToPath(key, ext);

    esp_http_client_config_t cfg = {};
    cfg.url            = dl->url.c_str();
    cfg.timeout_ms     = 30000;
    cfg.buffer_size    = 4096;

    esp_http_client_handle_t client = esp_http_client_init(&cfg);
    esp_err_t err = esp_http_client_open(client, 0);

    bool success = false;

    if(err == ESP_OK) {
        int content_len = esp_http_client_fetch_headers(client);
        (void)content_len;

        FILE* f = fopen(path.c_str(), "wb");
        if(f) {
            char buf[4096];
            int read_len;
            while((read_len = esp_http_client_read(client, buf, sizeof(buf))) > 0) {
                fwrite(buf, 1, read_len, f);
            }
            fclose(f);
            success = (read_len == 0); /* 0 = clean EOF */
            if(!success) {
                remove(path.c_str());
                ESP_LOGE(TAG, "Download error, partial file deleted");
            } else {
                ESP_LOGI(TAG, "Cached to %s", path.c_str());
            }
        } else {
            ESP_LOGE(TAG, "Cannot open cache file: %s (errno %d)", path.c_str(), errno);
        }
    } else {
        ESP_LOGE(TAG, "HTTP open failed: %s", esp_err_to_name(err));
    }

    esp_http_client_cleanup(client);

    if(dl->onComplete) dl->onComplete(success);

    delete dl;
    vTaskDelete(NULL);
}

void CacheManager::downloadAsync(const std::string& url, std::function<void(bool)> onComplete) {
    if(url.empty()) return;

    auto* args = new DownloadArgs{ url, onComplete };
    xTaskCreate(downloadTask, "cache_dl", 8192, args, 3, NULL);
}

std::vector<CacheEntry> CacheManager::listEntries() const {
    std::vector<CacheEntry> entries;

    DIR* dir = opendir(CACHE_DIR);
    if(!dir) return entries;

    struct dirent* entry;
    while((entry = readdir(dir)) != NULL) {
        if(entry->d_name[0] == '.') continue;

        std::string name(entry->d_name);
        std::string full = std::string(CACHE_DIR) + "/" + name;

        struct stat st;
        size_t size = 0;
        if(stat(full.c_str(), &st) == 0) size = st.st_size;

        /* Key is filename without extension */
        size_t dot = name.rfind('.');
        std::string key = (dot != std::string::npos) ? name.substr(0, dot) : name;

        entries.push_back({ key, /*url unknown*/"", full, size });
    }
    closedir(dir);
    return entries;
}

bool CacheManager::deleteEntry(const std::string& key) {
    std::string path = findFileByKey(key);
    if(path.empty()) return false;
    return remove(path.c_str()) == 0;
}

void CacheManager::deleteAll() {
    DIR* dir = opendir(CACHE_DIR);
    if(!dir) return;

    struct dirent* entry;
    while((entry = readdir(dir)) != NULL) {
        if(entry->d_name[0] == '.') continue;
        std::string full = std::string(CACHE_DIR) + "/" + entry->d_name;
        remove(full.c_str());
    }
    closedir(dir);
    ESP_LOGI(TAG, "Cache cleared");
}

size_t CacheManager::totalBytes() const {
    size_t total = 0;
    DIR* dir = opendir(CACHE_DIR);
    if(!dir) return 0;

    struct dirent* entry;
    while((entry = readdir(dir)) != NULL) {
        if(entry->d_name[0] == '.') continue;
        std::string full = std::string(CACHE_DIR) + "/" + entry->d_name;
        struct stat st;
        if(stat(full.c_str(), &st) == 0) total += st.st_size;
    }
    closedir(dir);
    return total;
}