import { Reader, ReaderMacros } from './reader.js';
import { DataTypes, Cons, Function, Nil, True, SpecialForm, Macro, Number, String, Symbol } from './datatypes.js';
import { Printer } from './printer.js';
import { Evaluator } from './evaluator.js';
import { Env } from './env.js';




export class Stream {
    onwrite = null;

    constructor(data = '') {
	this.data = Array.from(data);
    }
    
    readChar() {
	return this.data.shift();
    }
    
    peekChar() {
	return this.data[0];
    }
    
    pushData(data) {
	this.data.push(...Array.from(data));
	if (data && this.onwrite) {
	    this.onwrite(data);
	}
    }
    
    readData() {
	return this.data.splice(0).join("");
    }
}



export class Repl {
    stdin = new Stream();
    stdout = new Stream();
    env = new Env(
	null,
	{
	    'STANDARD-INPUT-STREAM': this.stdin,
	    'STANDARD-OUTPUT-STREAM': this.stdout,
	    'NIL': new Nil(),
	    'T': new True(),
	    '+': new Function(async operands => new Number(await Cons.reduce(operands, (rslt, i) => rslt + i.value, 0))),
	    '-': new Function(async operands => new Number(
		operands.cdr.type === DataTypes.Nil
		    ? -operands.car.value
		    : await Cons.reduce(operands.cdr, (rslt, i) => rslt - i.value, operands.car.value))),
	    '/': new Function(async operands => new Number(await operands.reduce((rslt, i) => rslt / i.value, 1))),
	    '*': new Function(async operands => new Number(await operands.reduce((rslt, i) => rslt * i.value, 1))),
	    '%': new Function(operands => new Number(operands.car.value % operands.cdr.car.value)),
	    'NOT': new Function(operands => operands.car.type === DataTypes.Nil ? new True() : new Nil()),
	    '=': new Function(operands => this.listCompare(operands, (a, b) => a === b)),
	    '<': new Function(operands => this.listCompare(operands, (a, b) => a < b)),
	    '<=': new Function(operands => this.listCompare(operands, (a, b) => a <= b)),
	    '>': new Function(operands => this.listCompare(operands, (a, b) => a > b)),
	    '>=': new Function(operands => this.listCompare(operands, (a, b) => a >= b)),
	    'PRINT': new Function(operands => {
		Printer.print(operands.car, this.env);
		return operands.car;
	    }),
	    'PRINC': new Function(operands => {
		Printer.princ(operands.car, this.env);
		return operands.car;
	    }),
	    'CONS': new Function(operands => new Cons(operands.car, operands.cdr.car)),
	    'LIST': new Function(operands => operands),
	    'CAR': new Function(operands => {
		if (operands.car.type === DataTypes.Nil) {
		    return new Nil();
		} else if (operands.car.type === DataTypes.Cons) {
		    return operands.car.car;
		}
		return new String('Can not car on not cons');
	    }),
	    'CDR': new Function(operands => {
		if (operands.car.type === DataTypes.Nil) {
		    return new Nil();
		} else if (operands.car.type === DataTypes.Cons) {
		    return operands.car.cdr
		}
		return new String('Can not cdr on not cons');
	    }),
	    'LET': new SpecialForm(async (sexp, env, macros) => {
		env = await Cons.reduce(
		    sexp.car,
		    async (prev, o) => {
			let env = new Env(prev, {[o.car.value]: new Nil()});
			Env.set(env, o.car.value, await Evaluator.eval(o.cdr.car, env, macros));
			return env;
		    },
		    env);
		return await Cons.reduce(sexp.cdr,
			    async (p, o) => await Evaluator.eval(o, env, macros),
					 null)}),
	    'SET': new SpecialForm(async (sexp, env, macros) => {
		const value = await Evaluator.eval(sexp.cdr.car, env, macros);
		Env.set(env, sexp.car.value, value);
		return value
	    }),
	    'DEF': new SpecialForm(async (sexp, env, macros) => {
		Env.set(this.env, sexp.car.value, await Evaluator.eval(sexp.cdr.car, env, macros));
		return sexp.car
	    }),
	    'FN': new SpecialForm((sexp, env, macros) => {
		const outer = env;
		return new Function(async (operands) => {
		    env = new Env(env,
				  sexp.car.type === DataTypes.Cons
				  ? await Cons.reduce(
				      Cons.zip(sexp.car, operands),
				      (prev, o) => ({...prev, [o.car.value]: o.cdr}),
				      {})
				  : {});
		    return await Cons.reduce(sexp.cdr,
				       async (_, o) => await Evaluator.eval(o, env, macros),
				       null);
		}, sexp, outer);
	    }),
	    'AND': new SpecialForm(async (sexp, env, macros) => {
		let last = new Nil();
		const f = async o => {
		    const cur = await Evaluator.eval(o.car, env, macros);
		    if (cur.type === DataTypes.Nil) {
			return last;
		    }
		    last = cur;
		    if (o.cdr.type === DataTypes.Nil) {
			return cur;
		    }
			    
		    return await f(o.cdr);
		};
		
		return await f(sexp);
	    }),
	    'OR': new SpecialForm(async (sexp, env, macros) => {
		let o = sexp;
		const f = async o => {
		    const cur = await Evaluator.eval(o.car, env, macros);
		    if (!(cur === DataTypes.Nil)) {
			return cur;
		    }
		    
		    if (o.cdr === DataTypes.Nil) {
			return new Nil();
		    }
		    
		    return await f(o.cdr);
		};
		
		return await f(sexp);
	    }),
	    'IF': new SpecialForm(async (sexp, env, macros) => {
		const cur = await Evaluator.eval(sexp.car, env, macros);
		return !(cur.type === DataTypes.Nil)
			  ? await Evaluator.eval(sexp.cdr.car, env, macros)
			  : await Evaluator.eval(sexp.cdr.cdr.car, env, macros);
	    }),
	    'QUASIQUOTE': new SpecialForm((sexp, env, macros) => {
		return this.unquote(sexp.car, env, macros);
	    }),
	    'QUOTE': new SpecialForm((sexp, env, macros) => {
		return sexp.car;
	    }),
	    'EVAL': new SpecialForm(async (sexp, env, macros) => {
		return await Evaluator.eval(
		    await Evaluator.eval(sexp.car, env, macros),
		    env,
		    macros);
	    }),
	    'EXPAND': new SpecialForm((sexp, env, macros) => {
		return Evaluator.expand(sexp.car, macros);
	    }),
	    'SAVE': new Function(() => {
		const converter = (key, val) => {
		    if (
			typeof val === 'function' ||
			    val && val.constructor === RegExp)
		    {
			return String(val);
		    }  else {
			return val;
		    }
		};
		window.localStorage.setItem(
		    'image',
		    JSON.stringify(
			repl_env.data,
			converter,
			2)
		);
		return new Nil();
	    }),
	    'LOAD': new Function(() => {
		const image = window.localStorage.getItem('image')
		const data = JSON.parse(image);
		const keys = Object.keys(data);
		for (let key of keys) {
		    const atom = data[key];
		    repl_env.set(key, eval(atom));
		}
		return new Nil();
	    }),
	    'GET-TIME': new Function(() => {
		return new Number(Date.now());
	    }),
	    'WAIT': new Function(operands => {
		return new Promise(resolve => setTimeout(_ => resolve(new Nil()), operands.car.value))
	    }),
	    'DO': new Function(operands => Cons.last(operands)),
	});
    
    macros = new Env(
	null,
	{
	    'MACRO': new SpecialForm((sexp, env) => this.macro(sexp)),
	    'DEFN': new Macro(
		operands => new Cons(new Symbol('DEF'),
				      new Cons(operands.car,
						new Cons(new Cons(new Symbol('FN'),
								    operands.cdr))))),
	    'DEFMACRO': new SpecialForm((sexp, env) => {
		Env.set(this.macros,
			sexp.car.value,
			this.macro(sexp.cdr));
		return new Cons(new Symbol("QUOTE"), new Cons(sexp.car));
	    }),
	}
    );

    async unquote(sexp, env, macros) {
	if (sexp.type === DataTypes.Cons) {
	    if (sexp.car.type === DataTypes.Symbol &&
		sexp.car.value == 'UNQUOTE') {
		return await Evaluator.eval(sexp.cdr.car, env, macros);
	    } else if (sexp.car.type === DataTypes.Cons &&
		       sexp.car.car.type === DataTypes.Symbol &&
		       sexp.car.car.value == 'UNQUOTE-SPLICING') {
		return await Evaluator.eval(sexp.car.cdr.car, env, macros);
	    }
	    return new Cons(
		await this.unquote(sexp.car, env, macros),
		await this.unquote(sexp.cdr, env, macros));
	}

	return sexp;
    }

    listCompare(list, comparer) {
	let compare = (last, list) => {
	    const result = comparer(last, list.car.value);
	    if (!result || list.cdr.type === DataTypes.Nil) {
		return result;
	    }

	    return compare(list.car.value, list.cdr);
	}

	return compare(list.car.value, list.cdr) ? new True() : new Nil();
    }

    // Return a new Promise always.



     macro(sexp) {
	return new Macro(async (operands) => {
	    let args = sexp.car;
	    let body = sexp.cdr;
	    let env = new Env(this.env,
			      args.type === DataTypes.Cons
			      ? await Cons.reduce(Cons.zip(args, operands),
				  (prev, o) => ({...prev,
						    [o.car.value]: o.cdr}),
				  {})
			      : {});

	    return await Cons.reduce(
		body,
		async (_, o) => await Evaluator.eval(o, env, this.macros),
		null);
	});
    }



    // READER

    constructor(loadFromFile, loadTest, read) {
	this.stdin.onwrite = () => this.readEvalPrint();

	Env.set(this.env, 'READ', new Function(async () => {
	    const rep = this.stdin.onwrite;
	    return new Promise(resolve => {
		read();
		this.stdin.onwrite = (a) => {
		    console.log(a);
		    this.stdin.onwrite = rep;
		    resolve(Reader.read(this.readerMacros, this.stdin));
		};
	    });
	}));

	Env.set(this.env, 'LOAD-FROM-FILE', new Function(async () => {
	    this.stdin.pushData(await loadFromFile());
	    return new Nil();
	}));

	Env.set(this.env, 'LOAD-TEST', new Function(async () => {
	    this.stdin.pushData(await loadTest());
	    return new Nil();
	}));

	this.readerMacros = new ReaderMacros();
	// List read macro
	ReaderMacros.setMacroCharacter(this.readerMacros, '(', (c, stream) => {
	    let cons;
	    let list;
	    let obj;
	    ReaderMacros.setMacroCharacter(this.readerMacros, ')', (c, stream) => {
		ReaderMacros.popMacroCharacter(this.readerMacros, c);
		return null;
	    });
	    while ((obj = Reader.read(this.readerMacros, stream))) {
		// list.push(obj);
		if (!cons) {
		    cons = new Cons(obj);
		    list = cons;
		} else {
		    cons = cons.cdr = new Cons(obj);
		}
	    }
	    if (list && list.car) {
		return list;
	    }
	    
	    return new Nil();
	});
	
	// String read macro
	ReaderMacros.setMacroCharacter(this.readerMacros, '"', (c, stream) => {
	    let char = null,
		lastc = null,
		data = '';
	    while(char = stream.readChar()) {
		if (char === '"' && lastc !== '\\') {
		    return new String(data);
		}
		
		data += char;
		lastc = char;
	    }
	    
	    return null;
	});
	
	// Quote read macro
	ReaderMacros.setMacroCharacter(this.readerMacros, '\'', (c, stream) => {
	    return new Cons(new Symbol('QUOTE'),
			    new Cons(Reader.read(this.readerMacros, stream)));
	});
	
	// Quasiquote read macro
	ReaderMacros.setMacroCharacter(this.readerMacros, '`', (c, stream) => {
	    return new Cons(new Symbol('QUASIQUOTE'),
			    new Cons(Reader.read(this.readerMacros, stream)));
	});
	
	// unquote read macro
	ReaderMacros.setMacroCharacter(this.readerMacros, ',', (c, stream) => {
	    return new Cons(new Symbol(stream.peekChar() == '@'
				       ? stream.readChar() && 'UNQUOTE-SPLICING'
				       : 'UNQUOTE'),
			    new Cons(Reader.read(this.readerMacros, stream)));
	});
    }

    async readEvalPrint() {
	if (!this.stdin.peekChar()) {
	    return;
	}

	const sexp = Reader.read(this.readerMacros, this.stdin);
	if (sexp) {
	    let evaluated;
	    try {
		evaluated = await Evaluator.eval(
		    sexp,
		    this.env,
		    this.macros);
	    } catch (e) {
		console.error(e);
		evaluated = new String(e);
	    }
		Printer.print(new String(""), this.env);
		Printer.prin1(evaluated, this.env);
		Printer.print(new String(""), this.env);
	}

	await this.readEvalPrint();
    }
}