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import type {JavaScriptLinked} from './types';
/**
* Inline JavaScript statements that are executed in main function body.
*/
export class CodegenStepExecJs {
constructor(public readonly js: string) {}
}
/**
* A step can be `CodegenStepExecJs` or some application specific step, which
* will later will need to be converted to `CodegenStepExecJs`.
*/
type JsonSerializerStep = CodegenStepExecJs | unknown;
/**
* Configuration options for {@link Codegen} instances.
*/
export interface CodegenOptions<Linkable = Record<string, unknown>> {
/**
* Inline JavaScript string that represents the arguments that will be passed
* to the main function body. Defaults to "r0", i.e. the first register.
*/
args?: string[];
/**
* Name of the generated function.
*/
name?: string;
/**
* Inline JavaScript statements, that execute at the beginning of the main
* function body.
*/
prologue?: string;
/**
* Inline JavaScript statements, that execute at the end of the main
* function body.
*/
epilogue?: string | (() => string);
/**
* Converts all steps to `CodegenStepExecJs`.
*/
processSteps?: (steps: JsonSerializerStep[]) => CodegenStepExecJs[];
/**
* Predefined list of dependencies that can be linked on demand. Dependency is
* linked with the name of the property and is linked only once.
*/
linkable?: Linkable;
}
export type CodegenGenerateOptions = Pick<CodegenOptions, 'name' | 'args' | 'prologue' | 'epilogue'>;
/**
* A helper class which helps with building JavaScript code for a single
* function. It keeps track of external dependencies, internally generated
* constants, and execution steps, which at the end are all converted to
* to an executable JavaScript function.
*
* The final output is a JavaScript function enclosed in a closure:
*
* ```js
* (function(d1, d2, d3) {
* var c1 = something;
* var c2 = something;
* var c3 = something;
* return function(r0) {
* var r1 = something;
* var r2 = something;
* var r3 = something;
* return something;
* }
* })
* ```
*
* Where `d*` are the external dependencies, `c*` are the internal constants,
* and `r*` are the local immutable infinite registers.
*/
export class Codegen<
Fn extends (...deps: any[]) => any = (...deps: unknown[]) => unknown,
Linkable = Record<string, unknown>,
> {
/** @ignore */
protected steps: JsonSerializerStep[] = [];
/** @ignore */
public options: Required<CodegenOptions<Linkable>>;
constructor(opts: CodegenOptions<Linkable>) {
this.options = {
args: ['r0'],
name: '',
prologue: '',
epilogue: '',
processSteps: (steps) => steps.filter((step) => step instanceof CodegenStepExecJs) as CodegenStepExecJs[],
linkable: {} as Linkable,
...opts,
};
this.registerCounter = this.options.args.length;
}
/**
* Add one or more JavaScript statements to the main function body.
*/
public js(js: string): void {
this.steps.push(new CodegenStepExecJs(js));
}
public var(expression?: string): string {
const r = this.getRegister();
if (expression) this.js('var ' + r + ' = ' + expression + ';');
else this.js('var ' + r + ';');
return r;
}
public if(condition: string, then: () => void, otherwise?: () => void): void {
this.js('if (' + condition + ') {');
then();
Iif (otherwise) {
this.js('} else {');
otherwise();
}
this.js('}');
}
public while(condition: string, block: () => void): void {
this.js('while (' + condition + ') {');
block();
this.js('}');
}
public doWhile(block: () => void, condition: string): void {
this.js('do {');
block();
this.js('} while (' + condition + ');');
}
public switch(
expression: string,
cases: [match: string | number | boolean | null, block: () => void, noBreak?: boolean][],
def?: () => void,
): void {
this.js('switch (' + expression + ') {');
for (const [match, block, noBreak] of cases) {
this.js('case ' + match + ': {');
block();
Iif (!noBreak) this.js('break;');
this.js('}');
}
Iif (def) {
this.js('default: {');
def();
this.js('}');
}
this.js('}');
}
public return(expression: string): void {
this.js('return ' + expression + ';');
}
/**
* Add any application specific execution step. Steps of `unknown` type
* later need to converted to `CodegenStepExecJs` steps in the `.processStep`
* callback.
*
* @param step A step in function execution logic.
*/
public step(step: unknown): void {
this.steps.push(step);
}
protected registerCounter: number;
/**
* Codegen uses the idea of infinite registers. It starts with `0` and
* increments it by one for each new register. Best practice is to use
* a new register for each new variable and keep them immutable.
*
* Usage:
*
* ```js
* const r = codegen.getRegister();
* codegen.js(`const ${r} = 1;`);
* ```
*
* @returns a unique identifier for a variable.
*/
public getRegister(): string {
return `r${this.registerCounter++}`;
}
public r(): string {
return this.getRegister();
}
/** @ignore */
protected dependencies: unknown[] = [];
protected dependencyNames: string[] = [];
/**
* Allows to wire up dependencies to the generated code.
*
* @param dep Any JavaScript dependency, could be a function, an object,
* or anything else.
* @param name Optional name of the dependency. If not provided, a unique
* name will be generated, which starts with `d` and a counter
* appended.
* @returns Returns the dependency name, a code symbol which can be used as
* variable name.
*/
public linkDependency(dep: unknown, name: string = 'd' + this.dependencies.length): string {
this.dependencies.push(dep);
this.dependencyNames.push(name);
return name;
}
/**
* Sames as {@link Codegen#linkDependency}, but allows to wire up multiple
* dependencies at once.
*/
public linkDependencies(deps: unknown[]): string[] {
return deps.map((dep) => this.linkDependency(dep));
}
protected linked: {[key: string]: 1} = {};
/**
* Link a dependency from the pre-defined `options.linkable` object. This method
* can be called many times with the same dependency name, the dependency will
* be linked only once.
*
* @param name Linkable dependency name.
*/
public link(name: keyof Linkable): void {
Iif (this.linked[name as string]) return;
this.linked[name as string] = 1;
this.linkDependency(this.options.linkable[name], name as string);
}
/** @ignore */
protected constants: string[] = [];
protected constantNames: string[] = [];
/**
* Allows to encode any code or value in the closure of the generated
* function.
*
* @param constant Any JavaScript value in string form.
* @param name Optional name of the constant. If not provided, a unique
* name will be generated, which starts with `c` and a counter
* appended.
* @returns Returns the constant name, a code symbol which can be used as
* variable name.
*/
public addConstant(constant: string, name: string = 'c' + this.constants.length): string {
this.constants.push(constant);
this.constantNames.push(name);
return name;
}
/**
* Sames as {@link Codegen#addConstant}, but allows to create multiple
* constants at once.
*/
public addConstants(constants: string[]): string[] {
return constants.map((constant) => this.addConstant(constant));
}
/**
* Returns generated JavaScript code with the dependency list.
*
* ```js
* const code = codegen.generate();
* const fn = eval(code.js)(...code.deps);
* const result = fn(...args);
* ```
*/
public generate(opts: CodegenGenerateOptions = {}): JavaScriptLinked<Fn> {
const {name, args, prologue, epilogue} = {...this.options, ...opts};
const steps = this.options.processSteps(this.steps);
const js = `(function(${this.dependencyNames.join(', ')}) {
${this.constants.map((constant, index) => `var ${this.constantNames[index]} = (${constant});`).join('\n')}
return ${name ? `function ${name}` : 'function'}(${args.join(',')}){
${prologue}
${steps.map((step) => (step as CodegenStepExecJs).js).join('\n')}
${typeof epilogue === 'function' ? epilogue() : epilogue || ''}
}})`;
// console.log(js);
return {
deps: this.dependencies,
js: js as JavaScriptLinked<Fn>['js'],
};
}
/**
* Compiles the generated JavaScript code into a function.
*
* @returns JavaScript function ready for execution.
*/
public compile(opts?: CodegenGenerateOptions): Fn {
const closure = this.generate(opts);
return compileClosure(closure);
}
}
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