linux-wallpaperengine-kde/src/WallpaperEngine/Scripting/ScriptEngine.cpp

#include "ScriptEngine.h"
#include "WallpaperEngine/Logging/Log.h"

#include <sstream>

using namespace WallpaperEngine::Scripting;
using namespace WallpaperEngine::Data::Model;

static std::unique_ptr<ScriptEngine> sScriptEngine;

ScriptEngine& ScriptEngine::instance () {
    if (!sScriptEngine) {
	sScriptEngine = std::unique_ptr<ScriptEngine> (new ScriptEngine ());
    }
    return *sScriptEngine;
}

ScriptEngine::ScriptEngine () {
    this->m_runtime = JS_NewRuntime ();
    if (!this->m_runtime) {
	sLog.error ("ScriptEngine: Failed to create JS runtime");
	return;
    }

    this->m_context = JS_NewContext (this->m_runtime);
    if (!this->m_context) {
	sLog.error ("ScriptEngine: Failed to create JS context");
	JS_FreeRuntime (this->m_runtime);
	this->m_runtime = nullptr;
	return;
    }
}

ScriptEngine::~ScriptEngine () {
    if (this->m_context) {
	JS_FreeContext (this->m_context);
    }
    if (this->m_runtime) {
	JS_FreeRuntime (this->m_runtime);
    }
}

JSValue ScriptEngine::dynamicValueToJS (const DynamicValue& value) const {
    JSContext* ctx = this->m_context;

    switch (value.getType ()) {
	case DynamicValue::Float:
	    return JS_NewFloat64 (ctx, value.getFloat ());
	case DynamicValue::Int:
	    return JS_NewInt32 (ctx, value.getInt ());
	case DynamicValue::Boolean:
	    return JS_NewBool (ctx, value.getBool ());
	case DynamicValue::Vec2: {
	    JSValue obj = JS_NewObject (ctx);
	    JS_SetPropertyStr (ctx, obj, "x", JS_NewFloat64 (ctx, value.getVec2 ().x));
	    JS_SetPropertyStr (ctx, obj, "y", JS_NewFloat64 (ctx, value.getVec2 ().y));
	    return obj;
	}
	case DynamicValue::Vec3: {
	    JSValue obj = JS_NewObject (ctx);
	    JS_SetPropertyStr (ctx, obj, "x", JS_NewFloat64 (ctx, value.getVec3 ().x));
	    JS_SetPropertyStr (ctx, obj, "y", JS_NewFloat64 (ctx, value.getVec3 ().y));
	    JS_SetPropertyStr (ctx, obj, "z", JS_NewFloat64 (ctx, value.getVec3 ().z));
	    return obj;
	}
	case DynamicValue::Vec4: {
	    JSValue obj = JS_NewObject (ctx);
	    JS_SetPropertyStr (ctx, obj, "x", JS_NewFloat64 (ctx, value.getVec4 ().x));
	    JS_SetPropertyStr (ctx, obj, "y", JS_NewFloat64 (ctx, value.getVec4 ().y));
	    JS_SetPropertyStr (ctx, obj, "z", JS_NewFloat64 (ctx, value.getVec4 ().z));
	    JS_SetPropertyStr (ctx, obj, "w", JS_NewFloat64 (ctx, value.getVec4 ().w));
	    return obj;
	}
	case DynamicValue::IVec2: {
	    JSValue obj = JS_NewObject (ctx);
	    JS_SetPropertyStr (ctx, obj, "x", JS_NewInt32 (ctx, value.getIVec2 ().x));
	    JS_SetPropertyStr (ctx, obj, "y", JS_NewInt32 (ctx, value.getIVec2 ().y));
	    return obj;
	}
	case DynamicValue::IVec3: {
	    JSValue obj = JS_NewObject (ctx);
	    JS_SetPropertyStr (ctx, obj, "x", JS_NewInt32 (ctx, value.getIVec3 ().x));
	    JS_SetPropertyStr (ctx, obj, "y", JS_NewInt32 (ctx, value.getIVec3 ().y));
	    JS_SetPropertyStr (ctx, obj, "z", JS_NewInt32 (ctx, value.getIVec3 ().z));
	    return obj;
	}
	case DynamicValue::IVec4: {
	    JSValue obj = JS_NewObject (ctx);
	    JS_SetPropertyStr (ctx, obj, "x", JS_NewInt32 (ctx, value.getIVec4 ().x));
	    JS_SetPropertyStr (ctx, obj, "y", JS_NewInt32 (ctx, value.getIVec4 ().y));
	    JS_SetPropertyStr (ctx, obj, "z", JS_NewInt32 (ctx, value.getIVec4 ().z));
	    JS_SetPropertyStr (ctx, obj, "w", JS_NewInt32 (ctx, value.getIVec4 ().w));
	    return obj;
	}
	default:
	    return JS_UNDEFINED;
    }
}

DynamicValueUniquePtr ScriptEngine::jsToDynamicValue (JSValue val, DynamicValue::UnderlyingType hint) const {
    JSContext* ctx = this->m_context;
    auto result = std::make_unique<DynamicValue> ();

    if (JS_IsException (val)) {
	return result;
    }

    // scalar types returned directly
    int tag = JS_VALUE_GET_TAG (val);
    if (tag == JS_TAG_INT) {
	int32_t i;
	JS_ToInt32 (ctx, &i, val);
	if (hint == DynamicValue::Float) {
	    result->update (static_cast<float> (i));
	} else {
	    result->update (static_cast<int> (i));
	}
	return result;
    }
    if (tag == JS_TAG_BOOL) {
	result->update (static_cast<bool> (JS_ToBool (ctx, val)));
	return result;
    }
    if (JS_TAG_IS_FLOAT64 (tag)) {
	double d;
	JS_ToFloat64 (ctx, &d, val);
	result->update (static_cast<float> (d));
	return result;
    }

    // object - extract x/y/z/w properties based on the hint type
    if (tag == JS_TAG_OBJECT) {
	auto readFloat = [&] (const char* prop) -> float {
	    JSValue v = JS_GetPropertyStr (ctx, val, prop);
	    double d = 0.0;
	    if (!JS_IsException (v) && !JS_IsUndefined (v)) {
		JS_ToFloat64 (ctx, &d, v);
	    }
	    JS_FreeValue (ctx, v);
	    return static_cast<float> (d);
	};

	auto readInt = [&] (const char* prop) -> int {
	    JSValue v = JS_GetPropertyStr (ctx, val, prop);
	    int32_t i = 0;
	    if (!JS_IsException (v) && !JS_IsUndefined (v)) {
		JS_ToInt32 (ctx, &i, v);
	    }
	    JS_FreeValue (ctx, v);
	    return static_cast<int> (i);
	};

	switch (hint) {
	    case DynamicValue::Vec2:
		result->update (glm::vec2 (readFloat ("x"), readFloat ("y")));
		break;
	    case DynamicValue::Vec3:
		result->update (glm::vec3 (readFloat ("x"), readFloat ("y"), readFloat ("z")));
		break;
	    case DynamicValue::Vec4:
		result->update (
		    glm::vec4 (readFloat ("x"), readFloat ("y"), readFloat ("z"), readFloat ("w")));
		break;
	    case DynamicValue::IVec2:
		result->update (glm::ivec2 (readInt ("x"), readInt ("y")));
		break;
	    case DynamicValue::IVec3:
		result->update (glm::ivec3 (readInt ("x"), readInt ("y"), readInt ("z")));
		break;
	    case DynamicValue::IVec4:
		result->update (
		    glm::ivec4 (readInt ("x"), readInt ("y"), readInt ("z"), readInt ("w")));
		break;
	    default: {
		// try to read as vec3 by default (most common for origin/angles)
		float x = readFloat ("x");
		float y = readFloat ("y");
		float z = readFloat ("z");
		result->update (glm::vec3 (x, y, z));
		break;
	    }
	}
	return result;
    }

    // fallback: try as float
    double d;
    if (JS_ToFloat64 (ctx, &d, val) == 0) {
	result->update (static_cast<float> (d));
    }
    return result;
}

/// Helper to check for and log JS exceptions
static void logJSException (JSContext* ctx, const char* context) {
    JSValue exc = JS_GetException (ctx);
    if (!JS_IsNull (exc) && !JS_IsUndefined (exc)) {
	const char* str = JS_ToCString (ctx, exc);
	if (str) {
	    sLog.error ("ScriptEngine [", context, "]: ", str);
	    JS_FreeCString (ctx, str);
	}
    }
    JS_FreeValue (ctx, exc);
}

DynamicValueUniquePtr ScriptEngine::evaluate (
    const std::string& scriptSource,
    const std::map<std::string, DynamicValue*>& scriptProperties,
    const DynamicValue& currentValue
) {
    if (!this->m_context) {
	sLog.error ("ScriptEngine: No JS context available");
	auto fallback = std::make_unique<DynamicValue> ();
	fallback->update (currentValue);
	return fallback;
    }

    JSContext* ctx = this->m_context;

    // Build the scriptProperties object that createScriptProperties() will return
    JSValue propsObj = JS_NewObject (ctx);
    for (const auto& [name, dynVal] : scriptProperties) {
	if (dynVal) {
	    JS_SetPropertyStr (ctx, propsObj, name.c_str (), this->dynamicValueToJS (*dynVal));
	}
    }

    // We need to rewrite the ES6 module into a regular script that we can evaluate
    // and extract the update() function from, because QuickJS module evaluation
    // via JS_EVAL_TYPE_MODULE doesn't easily let us get at exported functions
    // from C in a straightforward way.
    //
    // Strategy: Replace the ES6 module pattern with a plain script that:
    // 1. Has createScriptProperties() available as a global
    // 2. Defines update() in global scope
    // 3. We call update() with the value object
    //
    // The script pattern is always:
    //   'use strict';
    //   export var scriptProperties = createScriptProperties()...finish();
    //   export function update(value) { ... }
    //
    // We transform this to a self-contained IIFE that we evaluate directly.

    // Set createScriptProperties as a global that returns a builder
    // The builder supports .addSlider({...}).addCheckbox({...}).finish()
    // and returns an object with the property values

    // Create the builder as a JS object with fluent methods
    // that ultimately resolves to the propsObj
    std::ostringstream wrapper;
    wrapper << "(function() {\n"
	    << "  var __props = globalThis.__scriptProps;\n"
	    << "  function createScriptProperties() {\n"
	    << "    var builder = {\n"
	    << "      addSlider: function(opts) {\n"
	    << "        if (!(opts.name in __props)) __props[opts.name] = opts.value;\n"
	    << "        return builder;\n"
	    << "      },\n"
	    << "      addCheckbox: function(opts) {\n"
	    << "        if (!(opts.name in __props)) __props[opts.name] = opts.value;\n"
	    << "        return builder;\n"
	    << "      },\n"
	    << "      addCombo: function(opts) {\n"
	    << "        if (!(opts.name in __props)) __props[opts.name] = opts.value;\n"
	    << "        return builder;\n"
	    << "      },\n"
	    << "      addColor: function(opts) {\n"
	    << "        if (!(opts.name in __props)) __props[opts.name] = opts.value;\n"
	    << "        return builder;\n"
	    << "      },\n"
	    << "      addText: function(opts) {\n"
	    << "        if (!(opts.name in __props)) __props[opts.name] = opts.value;\n"
	    << "        return builder;\n"
	    << "      },\n"
	    << "      finish: function() { return __props; }\n"
	    << "    };\n"
	    << "    return builder;\n"
	    << "  }\n";

    // Strip 'use strict'; and export keywords, embed the script body
    std::string body = scriptSource;

    // Remove 'use strict'; declarations
    size_t pos;
    while ((pos = body.find ("'use strict';")) != std::string::npos) {
	body.erase (pos, 13);
    }
    while ((pos = body.find ("\"use strict\";")) != std::string::npos) {
	body.erase (pos, 13);
    }

    // Remove export keywords (export var ..., export function ...)
    while ((pos = body.find ("export ")) != std::string::npos) {
	body.erase (pos, 7);
    }

    wrapper << body << "\n"
	    << "  return update(globalThis.__currentValue);\n"
	    << "})();\n";

    std::string evalScript = wrapper.str ();

    // Set globals: __scriptProps and __currentValue
    JSValue globalObj = JS_GetGlobalObject (ctx);
    JS_SetPropertyStr (ctx, globalObj, "__scriptProps", JS_DupValue (ctx, propsObj));
    JS_SetPropertyStr (ctx, globalObj, "__currentValue", this->dynamicValueToJS (currentValue));

    // Evaluate
    JSValue result = JS_Eval (ctx, evalScript.c_str (), evalScript.size (), "<script>", JS_EVAL_TYPE_GLOBAL);

    // Clean up globals
    JS_SetPropertyStr (ctx, globalObj, "__scriptProps", JS_UNDEFINED);
    JS_SetPropertyStr (ctx, globalObj, "__currentValue", JS_UNDEFINED);
    JS_FreeValue (ctx, globalObj);
    JS_FreeValue (ctx, propsObj);

    if (JS_IsException (result)) {
	logJSException (ctx, "evaluate");
	JS_FreeValue (ctx, result);
	auto fallback = std::make_unique<DynamicValue> ();
	fallback->update (currentValue);
	return fallback;
    }

    auto dynResult = this->jsToDynamicValue (result, currentValue.getType ());
    JS_FreeValue (ctx, result);
    return dynResult;
}