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import { Reader, open, Buffer } from 'deno';import { stringsReader } from 'https://deno.land/x/io/util.ts';import { BufReader } from 'https://deno.land/x/io/bufio.ts';import escape from './escape.ts';
const globalEval = eval;const window = globalEval('this');
Object.defineProperty(window, '$$ESCAPE', {  value: escape,  writable: false,});
export interface Params {  [key: string]: any;}
enum ReadMode {  Normal,  Escaped,  Raw,  Comment,  Evaluate,}
enum Codes {  Begin = 60, // <  End = 62, // >  Percent = 37, // %  Escaped = 61, // =  Raw = 45, // -  Comment = 35, // #}
interface Template {  (params: Params): Reader;}
function NewTemplate(script: string): Template {  return (params: Params): Reader => {    for (const [k, v] of Object.entries(params)) {      window[k] = v;    }    window.$$OUTPUT = [];
    globalEval(script);
    const reader = stringsReader(String(window.$$OUTPUT.join('')));    for (const k of Object.keys(params)) {      delete window[k];    }    delete window.$$OUTPUT;    return reader;  };}
export async function compile(reader: Reader): Promise<Template> {  const src = new BufReader(reader);  const buf: Array<number> = [];  const statements: Array<string> = [];  const statementBuf = new Buffer();  let readMode: ReadMode = ReadMode.Normal;  const statementBufWrite = async (byte: number): Promise<number> =>    await statementBuf.write(new Uint8Array([byte]));
  while (true) {    const byte = await src.readByte();    if (byte < 0) {      break;    }
    buf.push(byte);    if (buf.length < 3) {      continue;    }
    if (readMode === ReadMode.Normal) {      // Detect ReadMode      if (buf[0] === Codes.Begin && buf[1] === Codes.Percent) {        switch (buf[2]) {          case Codes.Escaped:            readMode = ReadMode.Escaped;            break;          case Codes.Raw:            readMode = ReadMode.Raw;            break;          case Codes.Comment:            readMode = ReadMode.Comment;            break;          default:            readMode = ReadMode.Evaluate;            break;        }        statements.push(`$$OUTPUT.push(\`${statementBuf.toString()}\`);`);        statementBuf.reset();        buf.splice(0);        continue;      }      if (buf.length > 2) {        await statementBufWrite(buf.shift());      }      continue;    }
    // Finish current ReadMode    if (buf[1] === Codes.Percent && buf[2] === Codes.End) {      statementBufWrite(buf.shift());      buf.splice(0);      // Don't execute if ReadMode is Comment.      if (readMode !== ReadMode.Comment) {        switch (readMode) {          case ReadMode.Raw:            statements.push(`$$OUTPUT.push(${statementBuf.toString()});`);            break;          case ReadMode.Escaped:            statements.push(              `$$OUTPUT.push($$ESCAPE(${statementBuf.toString()}));`            );            break;          case ReadMode.Evaluate:            statements.push(statementBuf.toString());            break;        }      }      statementBuf.reset();      readMode = ReadMode.Normal;      continue;    }    await statementBufWrite(buf.shift());  }
  // Flush buffer  while (buf.length > 0) {    await statementBufWrite(buf.shift());  }  statements.push(`$$OUTPUT.push(\`${statementBuf.toString()}\`);`);  statementBuf.reset();
  return NewTemplate(statements.join(''));}
export async function render(body: string, params: Params): Promise<Reader> {  const reader = stringsReader(body);  const template = await compile(reader);  return template(params);}
export async function renderFile(  path: string,  params: Params): Promise<Reader> {  const file = await open(path);  const template = await compile(file);  file.close();  return template(params);}