import { Pattern, NamedPattern, Schema, Input, Environment, Ref, lookup } from "./meta";
import * as M from './meta';
import { Annotated, Bytes, Dictionary, Fold, fold, KeyedSet, Position, preserves, Record, Set, Tuple, Value } from "@preserves/core";
import { Formatter, parens, seq, Item, opseq, block, commas, brackets, anglebrackets, braces } from "./block";
import { refPosition } from "./reader";

export interface CompilerOptions {
    preservesModule?: string;
    defaultPointer?: Ref;
    warn?(message: string, pos: Position | null): void;
};

function fnblock(... items: Item[]): Item {
    return seq('((() => ', block(... items), ')())');
}

export function compile(env: Environment, schema: Schema, options: CompilerOptions = {}): string {
    const literals = new Dictionary<string, never>();
    const types: Array<Item> = [];
    const functions: Array<Item> = [];
    const imports = new KeyedSet<[string, string]>();
    let temps: Array<string> = [];
    let body: Array<Item> = [];
    let tempCounter = 0;
    const pointerName = Schema._.details(schema).get(M.$pointer);

    function gentemp(): string {
        const varname = '_tmp' + tempCounter++;
        temps.push(varname);
        return varname;
    }

    function literal(v: Input): Item {
        let varname = literals.get(v);
        if (varname === void 0) {
            const s = v.asPreservesText()
                .replace('_', '__')
                .replace('*', '_STAR_');
            varname = M.isValidToken('_' + s, true) ? '$' + s : '__lit' + literals.size;
            literals.set(v, varname);
        }
        return varname;
    }

    function emit(item: Item): void {
        body.push(item);
    }

    function collectBody(f: () => void): Item {
        const oldTemps = temps;
        const oldBody = body;
        temps = []
        body = [];
        f();
        const ts = temps;
        const result = body;
        temps = oldTemps;
        body = oldBody;
        return block(
            ... ts.length > 0 ? [seq('let ', commas(... ts), ': any')] : [],
            ... result);
    }

    function accumulateCompound(p: Pattern,
                                kFail: () => Item[],
                                kAcc: (temp: string) => Item[]): Item
    {
        const t = gentemp();
        return seq(`while (!d.closeCompound()) `, collectBody(() => {
            emit(seq(`${t} = void 0`));
            decoderFor(p, t);
            emit(seq(`if (${t} === void 0) `, block(
                ... kFail(),
                seq(`break`))));
            kAcc(t).forEach(emit);
        }));
    }

    function derefPattern(p: Pattern): Pattern {
        if (p.label === M.$ref) {
            return lookup(refPosition(p), p, env,
                          (p) => p,
                          (p) => p,
                          (_mod, _modPath, pp) => pp ?? p);
        } else {
            return p;
        }
    }

    function decoderForTuple(ps: Pattern[],
                             dest: string,
                             recordFields: boolean,
                             variablePattern: Pattern | undefined): void {
        const temps = ps.map(gentemp);
        function loop(i: number) {
            if (i < ps.length) {
                decoderFor(ps[i], temps[i]);
                emit(seq(`if (${temps[i]} !== void 0) `,
                         collectBody(() => loop(i + 1))));
            } else {
                if (variablePattern === void 0) {
                    emit(seq(`if (d.closeCompound()) ${dest} = `, brackets(... temps)));
                } else {
                    emit(block(
                        seq(`let vN: Array<`, typeFor(variablePattern),
                            `> | undefined = `, brackets(... temps)),
                        accumulateCompound(variablePattern,
                                           () => [`vN = void 0`],
                                           (t) => [`vN.push(${t})`]),
                        seq(`${dest} = vN`)));
                }
            }
        }
        if (recordFields) {
            loop(0);
        } else {
            emit(seq(`if (d.openSequence()) `, collectBody(() => loop(0))));
        }
    }

    function decoderFor(p: Pattern, dest: string, recordFields = false): void {
        switch (p.label) {
            case M.$atom:
                switch (p[0]) {
                    case M.$Boolean: emit(`${dest} = d.nextBoolean()`); break;
                    case M.$Float: emit(`${dest} = d.nextFloat()`); break;
                    case M.$Double: emit(`${dest} = d.nextDouble()`); break;
                    case M.$SignedInteger: emit(`${dest} = d.nextSignedInteger()`); break;
                    case M.$String: emit(`${dest} = d.nextString()`); break;
                    case M.$ByteString: emit(`${dest} = d.nextByteString()`); break;
                    case M.$Symbol: emit(`${dest} = d.nextSymbol()`); break;
                }
                break;
            case M.$lit: {
                let n: string;
                switch (typeof p[0]) {
                    case 'boolean': n = `d.nextBoolean()`; break;
                    case 'string': n = `d.nextString()`; break;
                    case 'number': n = `d.nextSignedInteger()`; break;
                    case 'symbol': n = `d.nextSymbol()`; break;
                    default: n = `d.next()`; break;
                }
                emit(`${dest} = _.asLiteral(${n}, ${literal(p[0])})`);
                break;
            }
            case M.$ref:
                lookup(refPosition(p), p, env,
                       (_p) => emit(`${dest} = decode${p[1].description!}(d)`),
                       (p) => decoderFor(p, dest),
                       (mod, modPath,_p) => {
                           imports.add([mod, modPath]);
                           emit(`${dest} = ${mod}.decode${p[1].description!}(d)`);
                       });
                break;
            case M.$or: {
                const alts = p[0];
                const recs = alts.map(derefPattern);
                if (recs.length > 1 && recs.every(pp => pp.label === M.$rec)) {
                    // Hoist the record check up.
                    // This is pretty hacky. If we lift the level of
                    // discourse a little, we can do this
                    // automatically and generically...
                    emit(seq(`if (d.openRecord()) `, collectBody(() => {
                        const label = gentemp();
                        emit(seq(`${label} = d.next()`));
                        const mark = gentemp();
                        emit(seq(`${mark} = d.mark()`));
                        function loop(i: number) {
                            const alt = recs[i];
                            if (alt.label !== M.$rec) return; // avoid a cast
                            emit(seq(`if (`, predicateFor(label, alt[0]), `) `, collectBody(() => {
                                const fs = gentemp();
                                decoderFor(alt[1], fs, true);
                                emit(seq(`if (${fs} !== void 0) ${dest} = _.Record`,
                                         anglebrackets(typeFor(alt[0]), typeFor(alt[1])),
                                         parens(seq(label, ` as any`),
                                                seq(fs, ` as any`))));
                            })));
                            if (i < recs.length - 1) {
                                emit(seq(`if (${dest} === void 0) `, collectBody(() => {
                                    emit(`d.restoreMark(${mark})`);
                                    loop(i + 1);
                                })));
                            }
                        }
                        loop(0);
                    })));
                } else {
                    switch (alts.length) {
                        case 0: break; // assume dest is already void 0
                        case 1: decoderFor(alts[0], dest); break;
                        default: {
                            const mark = gentemp();
                            emit(`${mark} = d.mark()`);
                            function loop(i: number) {
                                decoderFor(alts[i], dest);
                                if (i < alts.length - 1) {
                                    emit(seq(`if (${dest} === void 0) `, collectBody(() => {
                                        emit(`d.restoreMark(${mark})`);
                                        loop(i + 1);
                                    })));
                                }
                            }
                            loop(0);
                            break;
                        }
                    }
                }
                break;
            }
            case M.$and:
                switch (p[0].length) {
                    case 0: emit(`${dest} = d.next()`); break;
                    case 1: decoderFor(p[0][0], dest); break;
                    default: {
                        const [pp0, ... ppN] = p[0];
                        decoderFor(pp0, dest);
                        const otherChecks =
                            opseq('true', ' && ', ... ppN.map(pp => predicateFor(dest, pp)));
                        emit(seq(`if (!`, otherChecks, `) ${dest} = void 0`));
                        break;
                    }
                }
                break;
            case M.$pointer:
                emit(`${dest} = _decodePtr(d)`);
                break;
            case M.$rec:
                // assume dest is already void 0
                emit(seq(`if (d.openRecord()) `, collectBody(() => {
                    const label = gentemp();
                    decoderFor(p[0], label);
                    emit(seq(`if (${label} !== void 0) `,
                             collectBody(() => {
                                 const fs = gentemp();
                                 decoderFor(p[1], fs, true);
                                 emit(seq(
                                     `if (${fs} !== void 0) ${dest} = _.Record`,
                                     anglebrackets(typeFor(p[0]), typeFor(p[1])),
                                     parens(seq(label, ` as any`),
                                            seq(fs, ` as any`))));
                             })));
                })));
                break;
            case M.$tuple:
                // assume dest is already void 0
                decoderForTuple(p[0].map(unname), dest, recordFields, void 0);
                break;
            case M.$tuple_STAR_:
                // assume dest is already void 0
                decoderForTuple(p[0].map(unname), dest, recordFields, unname(p[1]));
                break;
            case M.$setof:
                // assume dest is already void 0
                emit(seq(`if (d.openSet()) `, collectBody(() => {
                    emit(seq(`let r: `, typeFor(p), ` | undefined = new _.KeyedSet()`));
                    emit(accumulateCompound(p[0],
                                            () => [`r = void 0`],
                                            (t) => [`r.add(${t})`]));
                    emit(`${dest} = r`);
                })));
                break;
            case M.$dictof:
                // assume dest is already void 0
                emit(seq(`if (d.openDictionary()) `, collectBody(() => {
                    emit(seq(`let r: `, typeFor(p), ` | undefined = new _.KeyedDictionary()`));
                    emit(seq(`while (!d.closeCompound()) `, collectBody(() => {
                        emit(seq(`let K: undefined | `, typeFor(p[0]), ` = void 0`));
                        decoderFor(p[0], 'K');
                        emit(seq(`if (K === void 0) { r = void 0; break; }`));
                        emit(seq(`let V: undefined | `, typeFor(p[1]), ` = void 0`));
                        decoderFor(p[1], 'V');
                        emit(seq(`if (V === void 0) { r = void 0; break; }`));
                        emit(seq(`r.set(K, V)`));
                    })));
                    emit(seq(`${dest} = r`));
                })));
                break;
            case M.$dict:
                emit(seq(`${dest} = d.next()`));
                emit(seq(
                    `if (${dest} !== void 0 && !(`, predicateFor(dest, p), `)) ${dest} = void 0`));
                break;
            default:
                ((_p: never) => {})(p);
                throw new Error("Unreachable");
        }
    }

    function typeFor(p: Pattern): Item {
        switch (p.label) {
            case M.$atom:
                switch (p[0]) {
                    case M.$Boolean: return `boolean`;
                    case M.$Float: return `_.SingleFloat`;
                    case M.$Double: return `_.DoubleFloat`;
                    case M.$SignedInteger: return `number`;
                    case M.$String: return `string`;
                    case M.$ByteString: return `_.Bytes`;
                    case M.$Symbol: return `symbol`;
                }
            case M.$lit:
                return `(typeof ${literal(p[0])})`;
            case M.$ref:
                return lookup(refPosition(p), p, env,
                              (_p) => p[1].description!,
                              (p) => typeFor(p),
                              (mod, modPath,_p) => {
                                  imports.add([mod, modPath]);
                                  return `${mod}.${p[1].description!}`;
                              });
            case M.$or:
                return opseq('never', ' | ', ... p[0].map(pp => typeFor(pp)));
            case M.$and:
                return opseq('_val', ' & ', ... p[0].map(pp => typeFor(pp)));
            case M.$pointer:
                return `_ptr`;
            case M.$rec:
                return seq('_.Record', anglebrackets(typeFor(p[0]), typeFor(p[1]), '_ptr'));
            case M.$tuple:
                return brackets(... p[0].map(pp => typeFor(unname(pp))));
            case M.$tuple_STAR_:
                if (p[0].length === 0) {
                    return seq('Array<', typeFor(unname(p[1])), '>');
                } else {
                    return brackets(... p[0].map(pp => typeFor(unname(pp))),
                                    seq('... Array<', typeFor(unname(p[1])), '>'));
                }
            case M.$setof:
                return seq('_.KeyedSet', anglebrackets(typeFor(p[0]), '_ptr'));
            case M.$dictof:
                return seq('_.KeyedDictionary', anglebrackets(typeFor(p[0]), typeFor(p[1]), '_ptr'));
            case M.$dict:
                return parens(seq(
                    block(
                        ... Array.from(p[0]).map(([k, vp]) =>
                            seq(`get(k: typeof ${literal(k)}): `, typeFor(vp))),
                        ... Array.from(p[0]).map(([k, _vp]) =>
                            seq(`has(k: typeof ${literal(k)}): true`))),
                    ' & _.Dictionary<_val, _ptr>'));
            default:
                ((_p: never) => {})(p);
                throw new Error("Unreachable");
        }
    }

    function predicateFor(v: string, p: Pattern, recordOkAsTuple = false): Item {
        switch (p.label) {
            case M.$atom:
                switch (p[0]) {
                    case M.$Boolean: return `typeof ${v} === 'boolean'`;
                    case M.$Float: return `_.Float.isSingle(${v})`;
                    case M.$Double: return `_.Float.isDouble(${v})`;
                    case M.$SignedInteger: return `typeof ${v} === 'number'`;
                    case M.$String: return `typeof ${v} === 'string'`;
                    case M.$ByteString: return `_.Bytes.isBytes(${v})`;
                    case M.$Symbol: return `typeof ${v} === 'symbol'`;
                }
            case M.$lit:
                return `_.is(${v}, ${literal(p[0])})`;
            case M.$ref:
                return lookup(refPosition(p), p, env,
                              (_p) => `is${Ref._.name(p).description!}(${v})`,
                              (pp) => predicateFor(v, pp),
                              (mod, modPath, _p) => {
                                  imports.add([mod, modPath]);
                                  return `${mod}.is${Ref._.name(p).description!}(${v})`;
                              });
            case M.$or: {
                const alts = p[0];
                const recs = alts.map(derefPattern);
                if (recs.length > 1 && recs.every(pp => pp.label === M.$rec)) {
                    return seq(
                        `_.Record.isRecord<_val, _.Tuple<_val>, _ptr>(${v}) && `,
                        parens(opseq('false', ' || ',
                                     ... recs.map(r =>
                                         (r.label !== M.$rec) ? '' : parens(seq(
                                             predicateFor(`${v}.label`, r[0]),
                                             ' && ',
                                             predicateFor(v, r[1], true)))))));
                } else {
                    return opseq('false', ' || ', ... p[0].map(pp => predicateFor(v, pp)));
                }
            }
            case M.$and:
                return opseq('true', ' && ', ... p[0].map(pp => predicateFor(v, pp)));
            case M.$pointer:
                return `_.isPointer(${v})`;
            case M.$rec:
                return opseq('true', ' && ',
                             `_.Record.isRecord<_val, _.Tuple<_val>, _ptr>(${v})`,
                             predicateFor(`${v}.label`, p[0]),
                             predicateFor(v, p[1], true));
            case M.$tuple:
                return opseq('true', ' && ',
                             ... (recordOkAsTuple ? []
                                 : [`_.Array.isArray(${v})`, `!_.Record.isRecord<_val, _.Tuple<_val>, _ptr>(${v})`]),
                             `(${v}.length === ${p[0].length})`,
                             ... p[0].map((pp, i) => predicateFor(`${v}[${i}]`, unname(pp))));
            case M.$tuple_STAR_:
                return opseq('true', ' && ',
                             ... (recordOkAsTuple ? []
                                 : [`_.Array.isArray(${v})`, `!_.Record.isRecord<_val, _.Tuple<_val>, _ptr>(${v})`]),
                             `(${v}.length >= ${p[0].length})`,
                             seq(p[0].length > 0 ? `${v}.slice(${p[0].length})` : v,
                                 `.every(v => `,
                                 parens(predicateFor('v', unname(p[1]))),
                                 `)`),
                             ... p[0].map((pp, i) => predicateFor(`${v}[${i}]`, unname(pp))));
            case M.$setof:
                return opseq('true', ' && ',
                             `_.Set.isSet<_val>(${v})`,
                             fnblock(
                                 seq(`for (const vv of ${v}) `, block(
                                     seq('if (!(', predicateFor('vv', p[0]), ')) return false'))),
                                 seq('return true')));
            case M.$dictof:
                return opseq('true', ' && ',
                             `_.Dictionary.isDictionary<_val, _ptr>(${v})`,
                             fnblock(
                                 seq(`for (const e of ${v}) `, block(
                                     seq('if (!(', predicateFor('e[0]', p[0]), ')) return false'),
                                     seq('if (!(', predicateFor('e[1]', p[1]), ')) return false'))),
                                 seq('return true')));
            case M.$dict:
                return opseq('true', ' && ',
                             `_.Dictionary.isDictionary<_val, _ptr>(${v})`,
                             ... Array.from(p[0]).map(([k, vp]) => {
                                 const tmp = gentemp();
                                 return parens(seq(
                                     `(${tmp} = ${v}.get(${literal(k)})) !== void 0 && `,
                                     predicateFor(tmp, vp)));
                             }));
            default:
                ((_p: never) => {})(p);
                throw new Error("Unreachable");
        }
    }

    function unname(p: NamedPattern): Pattern {
        return (p.label === M.$named) ? p[1] : p;
    }

    function fieldName(np: NamedPattern, index: number): string {
        return (np.label === M.$named) ? np[0].description! : `_field${index}`;
    }

    function fieldEntry(np: NamedPattern, index: number): Item {
        return seq(JSON.stringify(fieldName(np, index)), ': ', typeFor(unname(np)));
    }

    for (const [name0, pattern] of Schema._.details(schema).get(M.$definitions)) {
        const name = name0 as symbol;
        temps = [];
        const recognizer = predicateFor('v', pattern);
        if (pattern.label === M.$rec &&
            pattern[0].label === M.$lit &&
            pattern[1].label === M.$tuple)
        {
            types.push(
                seq(`export const ${name.description!} = _.Record.makeConstructor<`,
                    braces(... pattern[1][0].map(fieldEntry)),
                    `, _ptr>()(${literal(pattern[0][0])}, `,
                    JSON.stringify(pattern[1][0].map(fieldName)), `);`));
        }
        types.push(
            seq(`export type ${name.description!} = `, typeFor(pattern), `;`));
        functions.push(
            seq(`export function is${name.description!}`,
                '(v: any): v is ', name.description!, ' ',
                block(
                    ... temps.length > 0 ? [seq('let ', commas(... temps), ': any')] : [],
                    seq('return ', recognizer))));
        functions.push(
            seq(`export function as${name.description!}`,
                '(v: any): ', name.description!, ' ',
                block(
                    seq(`if (!is${name.description!}(v)) `,
                        block(`throw new TypeError(\`Invalid ${name.description!}: \${_.stringify(v)}\`)`),
                        ' else ',
                        block(`return v`)))));

        functions.push(
            seq(`export function decode${name.description!}`,
                `(d: _.TypedDecoder<_ptr>): ${name.description!} | undefined `,
                collectBody(() => {
                    emit(seq(`let result`));
                    decoderFor(pattern, 'result');
                    emit(seq(`return result`));
                })));
    }

    types.push(seq('export type _ptr = ', pointerName === false ? 'never' : typeFor(pointerName), `;`));
    types.push(`export type _val = _.Value<_ptr>;`);
    functions.push(seq(`export const _decodePtr = `,
                       (pointerName === false
                           ? '() => { throw new _.DecodeError("Pointers forbidden"); }'
                           : seq(`(d: _.TypedDecoder<_ptr>) => `,
                                 collectBody(() => {
                                     emit(seq(`let result`));
                                     decoderFor(pointerName, 'result');
                                     emit(seq(`return result`));
                                 }))),
                       `;`));

    const f = new Formatter();
    f.write(`import * as _ from ${JSON.stringify(options.preservesModule ?? '@preserves/core')};\n`);
    imports.forEach(([identifier, path]) => {
        f.write(`import * as ${identifier} from ${JSON.stringify(path)};\n`);
    });
    f.newline();

    const sortedLiterals = Array.from(literals);
    sortedLiterals.sort((a, b) => a[1] < b[1] ? -1 : a[1] === b[1] ? 0 : 1);
    for (const [lit, varname] of sortedLiterals) {
        f.write(seq(`export const ${varname} = `, sourceCodeFor(lit), `;\n`));
    }
    f.newline();

    types.forEach(t => {
        f.write(t);
        f.newline();
        f.newline();
    });
    f.newline();

    functions.forEach(p => {
        f.write(p);
        f.newline();
        f.newline();
    });

    return f.toString();
}

export function stringSource(s: string) {
    return JSON.stringify(s);
}

export function sourceCodeFor(v: Value<any>): Item {
    return fold(v, {
        boolean(b: boolean): Item { return b.toString(); },
        single(f: number): Item { return f.toString(); },
        double(f: number): Item { return f.toString(); },
        integer(i: number): Item { return i.toString(); },
        string(s: string): Item { return stringSource(s); },
        bytes(b: Bytes): Item {
            return seq(`Uint8Array.from(`, brackets(... Array.from(b).map(b => b.toString())), `)`);
        },
        symbol(s: symbol): Item { return `Symbol.for(${stringSource(s.description!)})`; },

        record(r: Record<Value<any>, Tuple<Value<any>>, any>, k: Fold<any, Item>): Item {
            return seq(`_.Record<_val, _.Tuple<_val>, _ptr>`, parens(k(r.label), brackets(... r.map(k))));
        },
        array(a: Array<Value<any>>, k: Fold<any, Item>): Item {
            return brackets(... a.map(k));
        },
        set(s: Set<any>, k: Fold<any, Item>): Item {
            return seq('new _.Set<_val>', parens(brackets(... Array.from(s).map(k))));
        },
        dictionary(d: Dictionary<Value<any>, any>, k: Fold<any, Item>): Item {
            return seq('new _.Dictionary<_val, _ptr>', parens(brackets(... Array.from(d).map(([kk,vv]) =>
                brackets(k(kk), k(vv))))));
        },

        annotated(a: Annotated<any>, k: Fold<any, Item>): Item {
            return seq('_.annotate<_ptr>', parens(k(a.item), ... a.annotations.map(k)));
        },

        pointer(t: any, _k: Fold<any, Item>): Item {
            throw new Error(preserves`Cannot emit source code for construction of pointer ${t}`);
        },
    });
}