Add redis support

CMakeLists.txt

@@ -1,11 +1,14 @@
 cmake_minimum_required(VERSION 3.16)
 
-project(pixwhile CXX)
+project(pixwhile C CXX)
 
 
 find_package(nlohmann_json REQUIRED)
 set(HTTPLIB_REQUIRE_OPENSSL ON)
 add_subdirectory(thirdparty/httplib)
+find_package(PkgConfig REQUIRED)
+pkg_check_modules(HIREDIS REQUIRED hiredis)
+
 
 if (CMAKE_BUILD_TYPE MATCHES "Debug")
     if (NOT FLAGS)
@@ -23,15 +26,15 @@ list(APPEND FLAGS -Werror -Wall -Wextra -Wshadow -Wpedantic -Wno-gnu-anonymous-s
 add_link_options(${FLAGS})
 
 
-add_executable(${PROJECT_NAME} main.cpp misc.cpp config.cpp servehelper.cpp numberhelper.cpp pixivclient.cpp pixivmodels.cpp
-    blankie/serializer.cpp blankie/escape.cpp blankie/murl.cpp
-    routes/home.cpp routes/css.cpp routes/artworks.cpp routes/tags.cpp routes/users/common.cpp routes/users/illustrations.cpp)
+add_executable(${PROJECT_NAME} main.cpp misc.cpp config.cpp servehelper.cpp numberhelper.cpp pixivclient.cpp pixivmodels.cpp hiredis_wrapper.cpp
+    routes/home.cpp routes/css.cpp routes/artworks.cpp routes/tags.cpp routes/guess_extension.cpp routes/users/common.cpp routes/users/illustrations.cpp
+    blankie/serializer.cpp blankie/escape.cpp blankie/murl.cpp)
 set_target_properties(${PROJECT_NAME}
     PROPERTIES
         CXX_STANDARD 20
         CXX_STANDARD_REQUIRED YES
         CXX_EXTENSIONS NO
 )
-target_include_directories(${PROJECT_NAME} PRIVATE thirdparty)
-target_link_libraries(${PROJECT_NAME} PRIVATE nlohmann_json::nlohmann_json httplib::httplib)
+target_include_directories(${PROJECT_NAME} PRIVATE thirdparty ${HIREDIS_INCLUDE_DIRS})
+target_link_libraries(${PROJECT_NAME} PRIVATE nlohmann_json::nlohmann_json httplib::httplib ${HIREDIS_LINK_LIBRARIES})
 target_compile_options(${PROJECT_NAME} PRIVATE ${FLAGS})

RUNNING.md

@@ -17,6 +17,15 @@ liking. Here's a list of what they are:
 - `bind_port` (zero or positive integer): What port to bind to
 - `image_proxy_url` (string): URL to proxy images to (see https://pixiv.cat/reverseproxy.html), a trailing slash is not needed
 - `canonical_origin` (string or null): A fallback canonical origin if set, useful if you're, say, running Pixwhile behind Ngrok
+- `redis` (object)
+  - `enabled` (boolean)
+  - `connection` (object)
+    - `type` ("ip" or "unix"): Whether to connect to redis via TCP or UNIX domain sockets
+    - `address` (string or null): If `type` is "ip", the address to connect to. Ignored otherwise
+    - `port` (int or null): If `type` is "ip", the port to connect to. Ignored otherwise
+    - `unix` (string or null): If `type` is "unix", the path to redis' socket. Ignored otherwise
+  - `username` (string or null): Optional username for authentication
+  - `password` (string or null): Optional password for authentication
 
 Pixwhile is intended to be run behind a reverse proxy (e.g. Nginx), so you
 should set your reverse proxy to proxy requests to

config.cpp

@@ -8,6 +8,33 @@ Config load_config(const char* path) {
     return nlohmann::json::parse(config_file.get());
 }
 
+RedisConfig get_redis_config(const nlohmann::json& j) {
+    using namespace std::string_literals;
+
+    RedisConfig redis_config;
+    const nlohmann::json& connection = j.at("connection");
+    const std::string& connection_type = connection.at("type").get_ref<const std::string&>();
+    if (connection_type == "ip") {
+        redis_config.connection_method = IPConnection{
+            connection.at("address").get<std::string>(),
+            connection.at("port").get<int>()
+        };
+    } else if (connection_type == "unix") {
+        redis_config.connection_method = UnixConnection{connection.at("unix").get<std::string>()};
+    } else {
+        throw std::invalid_argument("Unknown redis connection type: "s + connection_type);
+    }
+
+    if (j.at("username").is_string()) {
+        redis_config.username = j["username"].get<std::string>();
+    }
+    if (j.at("password").is_string()) {
+        redis_config.password = j["password"].get<std::string>();
+    }
+
+    return redis_config;
+}
+
 void from_json(const nlohmann::json& j, Config& config) {
     using namespace std::string_literals;
 
@@ -20,4 +47,8 @@ void from_json(const nlohmann::json& j, Config& config) {
     if (j.contains("canonical_origin") && j["canonical_origin"].is_string()) {
         config.canonical_origin = j["canonical_origin"].get<std::string>();
     }
+
+    if (j.contains("redis") && j["redis"].at("enabled")) {
+        config.redis_config = get_redis_config(j["redis"]);
+    }
 }

config.h

@@ -1,14 +1,30 @@
 #pragma once
 
 #include <string>
+#include <variant>
 #include <nlohmann/json.hpp>
 #include "blankie/murl.h"
 
+struct IPConnection {
+    std::string address;
+    int port;
+};
+struct UnixConnection {
+    std::string unix;
+};
+
+struct RedisConfig {
+    std::variant<IPConnection, UnixConnection> connection_method;
+    std::optional<std::string> username;
+    std::optional<std::string> password;
+};
+
 struct Config {
     std::string bind_host = "127.0.0.1";
     int bind_port = 8080;
     blankie::murl::Url image_proxy_url{"https://i.pixiv.cat"};
     std::optional<std::string> canonical_origin;
+    std::optional<RedisConfig> redis_config;
 };
 
 Config load_config(const char* path);

example_config.json

@@ -2,5 +2,16 @@
     "bind_host": "127.0.0.1",
     "bind_port": 8080,
     "image_proxy_url": "https://i.pixiv.cat",
-    "canonical_origin": null
+    "canonical_origin": null,
+    "redis": {
+        "enabled": true,
+        "connection": {
+            "type": "ip",
+            "address": "127.0.0.1",
+            "port": 6389,
+            "unix": "/path/to/redis.sock"
+        },
+        "username": null,
+        "password": "one of the passwords of all time"
+    }
 }

hiredis_wrapper.cpp

@@ -0,0 +1,128 @@
+#include "hiredis_wrapper.h"
+
+Redis::Redis(const std::string& address, int port) {
+    this->_context = redisConnect(address.c_str(), port);
+    if (!this->_context) {
+        throw std::bad_alloc();
+    }
+    if (this->_context->err) {
+        RedisException e(this->_context->errstr);
+        redisFree(this->_context);
+        throw e;
+    }
+}
+Redis::Redis(const std::string& unix) {
+    this->_context = redisConnectUnix(unix.c_str());
+    if (!this->_context) {
+        throw std::bad_alloc();
+    }
+    if (this->_context->err) {
+        RedisException e(this->_context->errstr);
+        redisFree(this->_context);
+        throw e;
+    }
+}
+Redis::~Redis() {
+    redisFree(this->_context);
+}
+
+void Redis::auth(const std::string& username, const std::string& password) {
+    RedisReply reply = this->command("AUTH %s %s", username.c_str(), password.c_str());
+    if (reply->type == REDIS_REPLY_STATUS) {
+        // good :D
+    } else {
+        throw std::runtime_error("AUTH gave an unexpected return type");
+    }
+}
+void Redis::auth(const std::string& password) {
+    RedisReply reply = this->command("AUTH %s", password.c_str());
+    if (reply->type == REDIS_REPLY_STATUS) {
+        // good :D
+    } else {
+        throw std::runtime_error("AUTH gave an unexpected return type");
+    }
+}
+
+time_t Redis::ttl(const std::string& key) {
+    RedisReply reply = this->command("TTL %s", key.c_str());
+    if (reply->type == REDIS_REPLY_INTEGER) {
+        return reply->integer;
+    } else {
+        throw std::runtime_error("TTL gave an unexpected return type");
+    }
+}
+
+bool Redis::expire(const std::string& key, time_t expiry) {
+    RedisReply reply = this->command("EXPIRE %s %d", key.c_str(), expiry);
+
+    if (reply->type == REDIS_REPLY_INTEGER) {
+        return reply->integer == 1;
+    } else {
+        throw std::runtime_error("EXPIRE gave an unexpected return type");
+    }
+}
+
+bool Redis::expire_nx(const std::string& key, time_t expiry) {
+    if (this->_fake_expire_nx) {
+        time_t current_expiry = this->ttl(key);
+        if (current_expiry < 0) {
+            return this->expire(key, expiry);
+        }
+        return false;
+    }
+
+    RedisReply reply(nullptr, freeReplyObject);
+    try{
+        reply = this->command("EXPIRE %s %d NX", key.c_str(), expiry);
+    } catch (const RedisException& e) {
+        if (e.error == "ERR wrong number of arguments for 'expire' command") {
+            this->_fake_expire_nx = true;
+            return this->expire_nx(key, expiry);
+        }
+        throw;
+    }
+
+    if (reply->type == REDIS_REPLY_INTEGER) {
+        return reply->integer == 1;
+    } else {
+        throw std::runtime_error("EXPIRE NX gave an unexpected return type");
+    }
+}
+
+std::optional<std::string> Redis::get(const std::string& key) {
+    RedisReply reply = this->command("GET %s", key.c_str());
+    if (reply->type == REDIS_REPLY_STRING) {
+        return std::string(reply->str, reply->len);
+    } else if (reply->type == REDIS_REPLY_NIL) {
+        return std::nullopt;
+    } else {
+        throw std::runtime_error("GET gave an unexpected return type");
+    }
+}
+void Redis::set(const std::string& key, const std::string& value, time_t expiry) {
+    RedisReply reply = this->command("SET %s %s EX %d", key.c_str(), value.c_str(), expiry);
+    if (reply->type == REDIS_REPLY_STATUS) {
+        // good :D
+    } else {
+        throw std::runtime_error("SET gave an unexpected return type");
+    }
+}
+
+std::optional<std::string> Redis::hget(const std::string& key, const std::string& field) {
+    RedisReply reply = this->command("HGET %s %s", key.c_str(), field.c_str());
+    if (reply->type == REDIS_REPLY_STRING) {
+        return std::string(reply->str, reply->len);
+    } else if (reply->type == REDIS_REPLY_NIL) {
+        return std::nullopt;
+    } else {
+        throw std::runtime_error("HGET gave an unexpected return type");
+    }
+}
+void Redis::hset(const std::string& key, const std::string& field, const std::string& value) {
+    RedisReply reply = this->command("HSET %s %s %s", key.c_str(), field.c_str(), value.c_str());
+    if (reply->type == REDIS_REPLY_INTEGER) {
+        // good :D
+    } else {
+        throw std::runtime_error("SET gave an unexpected return type");
+    }
+}

hiredis_wrapper.h

@@ -0,0 +1,70 @@
+#pragma once
+
+#include <string>
+#include <memory>
+#include <optional>
+#include <exception>
+
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wc99-extensions"
+#pragma GCC diagnostic ignored "-Wconversion"
+#include <hiredis.h>
+#pragma GCC diagnostic pop
+
+class RedisException : public std::exception {
+public:
+    RedisException(const char* error_) : error(error_) {}
+    RedisException(const char* error_, size_t length) : error(error_, length) {}
+
+    const char* what() const noexcept {
+        return this->error.c_str();
+    }
+
+    std::string error;
+};
+
+using RedisReply = std::unique_ptr<redisReply, decltype(&freeReplyObject)>;
+
+class Redis {
+public:
+    Redis(const Redis&) = delete;
+    Redis operator=(const Redis&) = delete;
+
+    Redis(const std::string& address, int port);
+    Redis(const std::string& unix);
+    ~Redis();
+
+    template<typename... Args>
+    RedisReply command(const char* format, Args... args) {
+        std::lock_guard<std::mutex> guard(this->_mutex);
+        redisReply* raw_reply = static_cast<redisReply*>(redisCommand(this->_context, format, args...));
+        if (!raw_reply) {
+            throw RedisException(this->_context->errstr);
+        }
+
+        RedisReply reply(raw_reply, freeReplyObject);
+        if (reply->type == REDIS_REPLY_ERROR) {
+            throw RedisException(reply->str, reply->len);
+        }
+        return reply;
+    }
+
+    void auth(const std::string& username, const std::string& password);
+    void auth(const std::string& password);
+
+    time_t ttl(const std::string& key);
+    bool expire(const std::string& key, time_t expiry);
+    bool expire_nx(const std::string& key, time_t expiry);
+
+    std::optional<std::string> get(const std::string& key);
+    void set(const std::string& key, const std::string& value, time_t expiry);
+
+    std::optional<std::string> hget(const std::string& key, const std::string& field);
+    void hset(const std::string& key, const std::string& field, const std::string& value);
+
+private:
+    redisContext* _context;
+    std::mutex _mutex;
+
+    bool _fake_expire_nx = false;
+};

main.cpp

@@ -6,6 +6,7 @@
 #include "pixivclient.h"
 #include "servehelper.h"
 #include "routes/routes.h"
+#include "hiredis_wrapper.h"
 
 int main(int argc, char** argv) {
     if (argc != 2) {
@@ -20,9 +21,22 @@ int main(int argc, char** argv) {
         fprintf(stderr, "Failed to load config: %s\n", e.what());
         return 1;
     }
-
-    PixivClient pixiv_client;
+    std::optional<Redis> redis;
+    if (config.redis_config) {
+        if (const IPConnection* ip_connection = std::get_if<IPConnection>(&config.redis_config->connection_method)) {
+            redis.emplace(ip_connection->address, ip_connection->port);
+        } else if (const UnixConnection* unix_connection = std::get_if<UnixConnection>(&config.redis_config->connection_method)) {
+            redis.emplace(unix_connection->unix);
+        }
+        if (config.redis_config->username && config.redis_config->password) {
+            redis->auth(*config.redis_config->username, *config.redis_config->password);
+        } else if (config.redis_config->password) {
+            redis->auth(*config.redis_config->password);
+        }
+    }
+    PixivClient pixiv_client(redis ? &*redis : nullptr);
     httplib::Server server;
+
     server.Get("/", [&](const httplib::Request& req, httplib::Response& res) {
         home_route(req, res, config);
     });
@@ -73,23 +87,7 @@ int main(int argc, char** argv) {
     });
 
     server.Get("/guess_extension/i.pximg.net(/.+)", [&](const httplib::Request& req, httplib::Response& res) {
-        using namespace std::string_literals;
-
-        // rip query parameters, but they're not important anyway
-        std::string path = req.matches.str(1);
-        auto serve_extension = [&](const char* extension) {
-            if (!pixiv_client.i_pximg_url_valid(path + '.' + extension)) {
-                return false;
-            }
-            serve_redirect(req, res, config, proxy_image_url(req, config, "https://i.pximg.net" + path + '.' + extension), true);
-            return true;
-        };
-
-        if (serve_extension("png") || serve_extension("jpg")) {
-            return;
-        }
-        res.status = 500;
-        serve_error(req, res, config, "500: Internal Server Error", "Failed to guess file extension for https://i.pximg.net"s + path);
+        guess_extension_route(req, res, config, pixiv_client, redis ? &*redis : nullptr);
     });
 
 #ifndef NDEBUG

pixivclient.cpp

@@ -1,11 +1,16 @@
+#include <FastHash.h>
+
 #include "blankie/murl.h"
 #include "numberhelper.h"
 #include "pixivclient.h"
 
+using namespace std::string_literals;
+
 static const constexpr char* touch_user_agent = "Mozilla/5.0 (Android 12; Mobile; rv:97.0) Gecko/97.0 Firefox/97.0";
 static const constexpr char* desktop_user_agent = "Mozilla/5.0 (Windows NT 10.0; rv:111.0) Gecko/20100101 Firefox/111.0";
+static void to_lower(std::string& str);
 
-PixivClient::PixivClient() {
+PixivClient::PixivClient(Redis* redis) : _redis(redis) {
     this->_www_pixiv_net_client.set_keep_alive(true);
     this->_www_pixiv_net_client.set_default_headers({
         {"Cookie", "webp_available=1"}
@@ -17,10 +22,9 @@ PixivClient::PixivClient() {
 }
 
 User PixivClient::get_user(uint64_t user_id) {
-    httplib::Result res = this->_www_pixiv_net_client.Get("/touch/ajax/user/details", {
-        {"lang", "en"}, {"id", std::to_string(user_id)}
-    }, {{"User-Agent", touch_user_agent}});
-    return this->_handle_result(std::move(res)).at("user_details").get<User>();
+    nlohmann::json j = this->_call_api("pixwhile:user:"s + std::to_string(user_id), std::nullopt, 24 * 60 * 60,
+        "/touch/ajax/user/details", {{"lang", "en"}, {"id", std::to_string(user_id)}}, {{"User-Agent", touch_user_agent}});
+    return j.at("user_details").get<User>();
 }
 
 Illusts PixivClient::get_illusts(uint64_t user_id, size_t page) {
@@ -28,21 +32,21 @@ Illusts PixivClient::get_illusts(uint64_t user_id, size_t page) {
     if (page != 0) {
         params.insert({"p", std::to_string(page + 1)});
     }
-    httplib::Result res = this->_www_pixiv_net_client.Get("/touch/ajax/user/illusts", std::move(params), {{"User-Agent", touch_user_agent}});
-    return this->_handle_result(std::move(res)).get<Illusts>();
+
+    nlohmann::json j = this->_call_api("pixwhile:illusts:"s + std::to_string(user_id), std::to_string(page), 60 * 60,
+        "/touch/ajax/user/illusts", std::move(params), {{"User-Agent", touch_user_agent}});
+    return j.get<Illusts>();
 }
 
 Illust PixivClient::get_illust(uint64_t illust_id) {
-    httplib::Result res = this->_www_pixiv_net_client.Get("/touch/ajax/illust/details", {
-        {"lang", "en"}, {"illust_id", std::to_string(illust_id)}
-    }, {{"User-Agent", touch_user_agent}});
-    return this->_handle_result(std::move(res)).get<Illust>();
+    nlohmann::json j = this->_call_api("pixwhile:illust:"s + std::to_string(illust_id), std::nullopt, 24 * 60 * 60,
+        "/touch/ajax/illust/details", {{"lang", "en"}, {"illust_id", std::to_string(illust_id)}}, {{"User-Agent", touch_user_agent}});
+    return j.get<Illust>();
 }
 
-SearchResults PixivClient::search_illusts(const std::string& query, size_t page, const std::string& order) {
-    using namespace std::string_literals;
-
-    httplib::Result res = this->_www_pixiv_net_client.Get("/ajax/search/illustrations/"s + blankie::murl::escape(query), {
+SearchResults PixivClient::search_illusts(std::string query, size_t page, const std::string& order) {
+    to_lower(query);
+    httplib::Params params = {
         {"lang", "en"},
         {"mode", "all"},
         {"p", std::to_string(page + 1)},
@@ -50,18 +54,34 @@ SearchResults PixivClient::search_illusts(const std::string& query, size_t page,
         {"type", "illust_and_ugoira"},
         {"order", order},
         {"word", query}
-    }, {{"User-Agent", desktop_user_agent}});
-    return this->_handle_result(std::move(res)).get<SearchResults>();
+    };
+
+    std::string cache_key = "pixwhile:search:"s + order + ':' + std::to_string(FastHash(query.data(), query.size(), 0));
+    nlohmann::json j = this->_call_api(std::move(cache_key), std::to_string(page), 60 * 60,
+        "/ajax/search/illustrations/"s + blankie::murl::escape(std::move(query)), std::move(params), {{"User-Agent", desktop_user_agent}});
+    return j.get<SearchResults>();
+}
+
+std::vector<SearchSuggestion> PixivClient::get_search_suggestions(std::string query) {
+    to_lower(query);
+    std::string body = [&]() {
+        std::string cache_key = "pixwhile:searchsugg:"s + std::to_string(FastHash(query.data(), query.size(), 0));
+        std::optional<std::string> cached_body = this->_redis->get(cache_key);
+        if (cached_body) {
+            return std::move(*cached_body);
         }
 
-std::vector<SearchSuggestion> PixivClient::get_search_suggestions(const std::string& query) {
         httplib::Result res = this->_www_pixiv_net_client.Get("/rpc/cps.php", {
             {"lang", "en"}, {"keyword", query}
         }, {{"User-Agent", desktop_user_agent}, {"Referer", "https://www.pixiv.net/"}});
         if (!res) {
             throw HTTPLibException(res.error());
         }
-    nlohmann::json j = nlohmann::json::parse(std::move(res->body)).at("candidates");
+
+        this->_redis->set(std::move(cache_key), res->body, 24 * 60 * 60);
+        return std::move(res->body);
+    }();
+    nlohmann::json j = nlohmann::json::parse(std::move(body)).at("candidates");
 
     std::vector<SearchSuggestion> search_suggestions;
     search_suggestions.reserve(j.size());
@@ -76,16 +96,34 @@ std::vector<SearchSuggestion> PixivClient::get_search_suggestions(const std::str
     return search_suggestions;
 }
 
-nlohmann::json PixivClient::_handle_result(httplib::Result res) {
+nlohmann::json PixivClient::_call_api(std::string cache_key, std::optional<std::string> cache_field, time_t expiry,
+        std::string path, httplib::Params params, httplib::Headers headers) {
+    std::optional<std::string> success_body = !cache_field
+        ? this->_redis->get(cache_key)
+        : this->_redis->hget(cache_key, *cache_field);
+    if (success_body) {
+        return nlohmann::json::parse(std::move(*success_body));
+    }
+
+    httplib::Result res = this->_www_pixiv_net_client.Get(std::move(path), std::move(params), std::move(headers));
     if (!res) {
         throw HTTPLibException(res.error());
     }
-
     nlohmann::json j = nlohmann::json::parse(std::move(res->body));
     if (j.at("error")) {
         throw PixivException(res->status, j.at("message").get<std::string>());
     }
-    return j.at("body");
+
+    j = j.at("body");
+    // trim data sent to redis without making our own serialization of our objects
+    j.erase("ads");
+    if (!cache_field) {
+        this->_redis->set(std::move(cache_key), j.dump(), expiry);
+    } else {
+        this->_redis->hset(cache_key, std::move(*cache_field), j.dump());
+        this->_redis->expire_nx(std::move(cache_key), expiry);
+    }
+    return j;
 }
 
 bool PixivClient::i_pximg_url_valid(const std::string& path) {
@@ -95,3 +133,12 @@ bool PixivClient::i_pximg_url_valid(const std::string& path) {
     }
     return res->status >= 200 && res->status <= 200;
 }
+
+
+static void to_lower(std::string& str) {
+    for (size_t i = 0; i < str.size(); i++) {
+        if (str[i] >= 'A' && str[i] <= 'Z') {
+            str[i] = str[i] - 'A' + 'a';
+        }
+    }
+}

pixivclient.h

@@ -1,28 +1,31 @@
 #pragma once
 
 #include <vector>
-
-#include "pixivmodels.h"
 #include <httplib/httplib.h>
 #include <nlohmann/json.hpp>
 
+#include "pixivmodels.h"
+#include "hiredis_wrapper.h"
+
 class PixivClient {
 public:
-    PixivClient();
+    PixivClient(Redis* redis);
 
     User get_user(uint64_t user_id);
     Illusts get_illusts(uint64_t user_id, size_t page);
     Illust get_illust(uint64_t illust_id);
 
-    SearchResults search_illusts(const std::string& query, size_t page, const std::string& order);
-    std::vector<SearchSuggestion> get_search_suggestions(const std::string& query);
+    SearchResults search_illusts(std::string query, size_t page, const std::string& order);
+    std::vector<SearchSuggestion> get_search_suggestions(std::string query);
 
     bool i_pximg_url_valid(const std::string& path);
 
 private:
-    nlohmann::json _handle_result(httplib::Result res);
+    nlohmann::json _call_api(std::string cache_key, std::optional<std::string> cache_field, time_t expiry,
+            std::string path, httplib::Params params, httplib::Headers headers);
     httplib::Client _www_pixiv_net_client{"https://www.pixiv.net"};
     httplib::Client _i_pximg_net_client{"https://i.pximg.net"};
+    Redis* _redis;
 };
 
 class HTTPLibException : public std::exception {

routes/guess_extension.cpp

@@ -0,0 +1,46 @@
+#include <FastHash.h>
+
+#include "routes.h"
+#include "../servehelper.h"
+#include "../pixivclient.h"
+#include "../hiredis_wrapper.h"
+
+static inline std::optional<std::string> guess_extension(const std::string& path, PixivClient& pixiv_client);
+
+void guess_extension_route(const httplib::Request& req, httplib::Response& res, const Config& config, PixivClient& pixiv_client, Redis* redis) {
+    using namespace std::string_literals;
+
+    std::string path = req.matches.str(1);
+    std::string cache_key = "pixwhile:i.pximg.net:ext:"s + std::to_string(FastHash(path.data(), path.size(), 0));
+
+    std::optional<std::string> extension = redis
+        ? redis->get(cache_key)
+        : std::nullopt;
+    if (!extension) {
+        extension = guess_extension(path, pixiv_client);
+        if (!extension) {
+            res.status = 500;
+            serve_error(req, res, config, "500: Internal Server Error", "Failed to guess file extension for https://i.pximg.net"s + path);
+            return;
+        }
+        if (redis) {
+            redis->set(std::move(cache_key), *extension, 24 * 60 * 60);
+        }
+    }
+
+    serve_redirect(req, res, config, proxy_image_url(req, config, "https://i.pximg.net" + path + '.' + *extension), true);
+}
+
+static inline std::optional<std::string> guess_extension(const std::string& path, PixivClient& pixiv_client) {
+    auto guess_extension = [&](const char* extension) {
+        return pixiv_client.i_pximg_url_valid(path + '.' + extension);
+    };
+
+    if (guess_extension("png")) {
+        return "png";
+    } else if (guess_extension("jpg")) {
+        return "jpg";
+    } else {
+        return std::nullopt;
+    }
+}

routes/routes.h

@@ -4,6 +4,7 @@
 
 struct Config; // forward declaration from ../config.h
 class PixivClient; // forward declaration from ../pixivclient.h
+class Redis; // forward declaration from ../hiredis_wrapper.h
 
 extern const uint64_t css_hash;
 
@@ -12,3 +13,4 @@ void css_route(const httplib::Request& req, httplib::Response& res);
 void user_illustrations_route(const httplib::Request& req, httplib::Response& res, const Config& config, PixivClient& pixiv_client);
 void artworks_route(const httplib::Request& req, httplib::Response& res, const Config& config, PixivClient& pixiv_client);
 void tags_route(const httplib::Request& req, httplib::Response& res, const Config& config, PixivClient& pixiv_client);
+void guess_extension_route(const httplib::Request& req, httplib::Response& res, const Config& config, PixivClient& pixiv_client, Redis* redis);

thirdparty/FastHash.h

@@ -48,7 +48,7 @@
 //			(h) *= 0x2127599bf4325c37ULL;
 //			(h) ^= (h) >> 47; })
 
-constexpr uint64_t FastHash(const char* str, size_t size, uint64_t seed/*, uint64_t back = {}*/)
+constexpr uint64_t FastHash(const char* str, std::size_t size, uint64_t seed/*, uint64_t back = {}*/)
 {
 	auto const mix = [](uint64_t h)
 	{
@@ -62,7 +62,7 @@ constexpr uint64_t FastHash(const char* str, size_t size, uint64_t seed/*, uint6
 
 	uint64_t h = seed ^ (size * m);
 
-	for (size_t i = 0; i < size; i++)
+	for (std::size_t i = 0; i < size; i++)
 	{
 		h ^= mix(static_cast<uint64_t>(str[i]));
 		h *= m;