[api][feature][file] Add ID & Save preset as remix

The idea is to highlight AVS's remix culture by creating metadata to
both machine-readably identify presets globally, as well as keep track
of any presets the current preset was based on. This could, in the
future, enable a database of presets to trace inheritance connections
among other things.

To that end:
  - Add an "ID" parameter to the Root config that gets randomly
    assigned a UUID on first creation of a new preset. The ID does not
    change when the preset is saved, it's more of a "project id".
  - Add a "Based On" list parameter to the Root config that can record
    previous presets with ID, date, name and authors.
  - Add a `remix()` method to the Root effect, which switches some
    metadata and assigns a new ID and initial date.
  - Add an `as_remix` parameter to both `avs_preset_set()` and
    `avs_preset_save()` API functions. Setting this flag invokes the
    `remix()` method on the current Root before saving.

While not strictly related, also in this commit:
  - Split the Root config's "Date" field into initial date and last-
    edited date, to reflect both start of the preset and most recent
    version.
  - When creating a new preset give it a semi-random name of the
    format "Untitled Preset xxxxxxxxxx", where xx..xx is a 10-digit
    random alphanumeric suffix.

avs/vis_avs/avs.cpp

@@ -161,20 +161,23 @@ bool avs_preset_set(AVS_Handle avs, const char* preset) {
     return instance->preset_load(preset, false);
 }
 AVS_API
-bool avs_preset_save(AVS_Handle avs, const char* file_path, bool indent) {
+bool avs_preset_save(AVS_Handle avs,
+                     const char* file_path,
+                     bool as_remix,
+                     bool indent) {
     AVS_Instance* instance = get_instance_from_handle(avs);
     if (instance == nullptr) {
         return false;
     }
-    return instance->preset_save_file(file_path, indent);
+    return instance->preset_save_file(file_path, as_remix, indent);
 }
 AVS_API
-const char* avs_preset_get(AVS_Handle avs, bool indent) {
+const char* avs_preset_get(AVS_Handle avs, bool as_remix, bool indent) {
     AVS_Instance* instance = get_instance_from_handle(avs);
     if (instance == nullptr) {
         return nullptr;
     }
-    return instance->preset_save(indent);
+    return instance->preset_save(as_remix, indent);
 }
 AVS_API
 bool avs_preset_set_legacy(AVS_Handle avs,

avs/vis_avs/avs.h

@@ -266,15 +266,17 @@ bool avs_preset_load(AVS_Handle avs, const char* file_path);
 bool avs_preset_set(AVS_Handle avs, const char* preset);
 
 /**
- * Save the currently loaded preset to the given file path. If `indent` is `true`, the
+ * Save the currently loaded preset to the given file path. If `as_remix` is `true`, the
+ * preset's metadata will be refreshed, a new ID assigned and some of the old preset's
+ * metadata appended to the history list for the new preset. If `indent` is `true`, the
  * JSON will be indented with 4 spaces in the file. Otherwise it will be a single line.
  *
  * If `file_path` does not end in ".avs" it will be appended. Setting `file_path` to a
  * directory is an error.
  *
  * Returns `true` on success or `false` if saving fails for some reason.
  */
-bool avs_preset_save(AVS_Handle avs, const char* file_path, bool indent);
+bool avs_preset_save(AVS_Handle avs, const char* file_path, bool as_remix, bool indent);
 
 /**
  * Return the currently loaded preset's JSON string. If `indent` is `true`, the JSON
@@ -289,7 +291,7 @@ bool avs_preset_save(AVS_Handle avs, const char* file_path, bool indent);
  *
  * Returns `NULL` on error.
  */
-const char* avs_preset_get(AVS_Handle avs, bool indent);
+const char* avs_preset_get(AVS_Handle avs, bool as_remix, bool indent);
 
 /**
  * Load a preset from a legacy binary buffer.

avs/vis_avs/e_root.cpp

@@ -18,9 +18,24 @@
     (data[pos] | (data[pos + 1] << 8) | (data[pos + 2] << 16) | (data[pos + 3] << 24))
 
 constexpr Parameter Root_Info::author_parameters[];
+constexpr Parameter Root_Info::remix_parameters[];
 constexpr Parameter Root_Info::parameters[];
 
-E_Root::E_Root(AVS_Instance* avs) : Configurable_Effect(avs), buffers_saved(false) {}
+std::string random_preset_name_slug() {
+    static const char charset[] = "0123456789abcdefghijklmnopqrstuvwxyz";
+    std::string slug;
+    for (int i = 0; i < 10; i++) {
+        slug += charset[rand() % (sizeof(charset) - 1)];
+    }
+    return slug;
+}
+
+E_Root::E_Root(AVS_Instance* avs) : Configurable_Effect(avs), buffers_saved(false) {
+    this->config.date_init = current_date_str();
+    this->config.name = "Untitled Preset " + random_preset_name_slug();
+    log_info("Name: %s", this->config.name.c_str());
+    this->config.id = uuid4();
+}
 E_Root::~E_Root() {
     for (int i = 0; i < NBUF; i++) {
         free(this->buffers[i]);
@@ -30,6 +45,17 @@ E_Root::~E_Root() {
     }
 }
 
+void E_Root::remix() {
+    Root_RemixParent_Config remix_parent;
+    remix_parent.id = this->config.id;
+    remix_parent.name = this->config.name;
+    remix_parent.date = this->config.date_last;
+    remix_parent.authors = this->config.authors;
+    this->config.based_on.push_back(remix_parent);
+    this->config.id = uuid4();
+    this->config.date_init = current_date_str();
+}
+
 int E_Root::render(char visdata[2][2][576],
                    int is_beat,
                    int* framebuffer,

avs/vis_avs/e_root.h

@@ -11,11 +11,21 @@ struct Root_Author_Config : public Effect_Config {
     std::string name;
 };
 
+struct Root_BasedOn_Config : public Effect_Config {
+    std::string id;
+    std::string name;
+    std::string date;
+    std::vector<Root_Author_Config> authors;
+};
+
 struct Root_Config : public Effect_Config {
     bool clear = false;
     std::string name;
-    std::string date;
+    std::string date_init;
+    std::string date_last;
     std::vector<Root_Author_Config> authors;
+    std::string id;
+    std::vector<Root_BasedOn_Config> based_on;
 };
 
 struct Root_Info : public Effect_Info {
@@ -34,20 +44,51 @@ struct Root_Info : public Effect_Info {
                  "Role",
                  "'author', 'remixer', 'editor', 'curator' - or anything else")};
 
-    static constexpr uint32_t num_parameters = 4;
+    static constexpr uint32_t num_remix_parameters = 4;
+    static constexpr Parameter remix_parameters[num_remix_parameters] = {
+        P_STRING(offsetof(Root_BasedOn_Config, id), "ID", "UUID of the predecessor"),
+        P_STRING(offsetof(Root_BasedOn_Config, name),
+                 "Name",
+                 "Name of the predecessor"),
+        P_STRING(offsetof(Root_BasedOn_Config, date),
+                 "Date",
+                 "Last-edited date of the predecessor"),
+        P_LIST<Root_Author_Config>(offsetof(Root_BasedOn_Config, authors),
+                                   "Authors",
+                                   author_parameters,
+                                   num_author_parameters,
+                                   0,
+                                   0,
+                                   "Authors of the predecessor"),
+    };
+
+    static constexpr uint32_t num_parameters = 7;
     static constexpr Parameter parameters[num_parameters] = {
         P_BOOL(offsetof(Root_Config, clear),
                "Clear",
                "Clear the screen for every new frame"),
         P_STRING(offsetof(Root_Config, name), "Name", "Name of the preset"),
-        P_STRING(offsetof(Root_Config, date), "Date", "Date of the preset"),
+        P_STRING(offsetof(Root_Config, date_init),
+                 "Date Initial",
+                 "Date of preset's first save"),
+        P_STRING(offsetof(Root_Config, date_last),
+                 "Date Last",
+                 "Date of preset's latest save"),
         P_LIST<Root_Author_Config>(offsetof(Root_Config, authors),
                                    "Authors",
                                    author_parameters,
                                    num_author_parameters,
                                    0,
                                    0,
                                    "Authors of the preset"),
+        P_STRING(offsetof(Root_Config, id), "ID", "UUID of the preset"),
+        P_LIST<Root_BasedOn_Config>(offsetof(Root_Config, based_on),
+                                    "Based On",
+                                    remix_parameters,
+                                    num_remix_parameters,
+                                    0,
+                                    0,
+                                    "Previous presets used to create this one"),
     };
 
     virtual bool can_have_child_components() const { return true; }
@@ -69,6 +110,7 @@ class E_Root : public Configurable_Effect<Root_Info, Root_Config> {
     virtual void load_legacy(unsigned char* data, int len);
     virtual int save_legacy(unsigned char* data);
     virtual E_Root* clone() { return new E_Root(*this); }
+    void remix();
     int64_t get_num_renders() { return this->children.size(); }
     void start_buffer_context();
     void end_buffer_context();

avs/vis_avs/instance.cpp

@@ -177,8 +177,8 @@ bool AVS_Instance::preset_load_legacy(const uint8_t* preset,
     return false;
 }
 
-bool AVS_Instance::preset_save_file(const char* file_path, bool indent) {
-    auto preset_str = this->preset_save(indent);
+bool AVS_Instance::preset_save_file(const char* file_path, bool as_remix, bool indent) {
+    auto preset_str = this->preset_save(as_remix, indent);
     FILE* fp = fopen(file_path, "wb");
     if (fp != nullptr) {
         fwrite(preset_str, 1, strlen(preset_str), fp);
@@ -210,10 +210,14 @@ int AVS_Instance::preset_save_file_legacy(const char* file_path) {
     return result;
 }
 
-const char* AVS_Instance::preset_save(bool indent) {
+const char* AVS_Instance::preset_save(bool as_remix, bool indent) {
     json j;
     j["preset format version"] = "0";
     j["avs version"] = "2.81.4";
+    if (as_remix) {
+        this->root.remix();
+    }
+    this->root.config.date_last = current_date_str();
     try {
         j.update(this->root.save());
         j.erase("effect");