preserves/implementations/javascript/packages/schema/src/compiler/converter.ts

import { FunctionContext } from "./context";
import * as M from '../meta';
import { block, Item, seq } from "./block";
import { typeFor } from "./type";
import { refPosition } from "../reader";

export function converterForDefinition(
    ctx: FunctionContext,
    p: M.Definition,
    src: string,
    dest: string): Item[]
{
    if (p.label === M.$or) {
        const alts = p[0];
        function loop(i: number): Item[] {
            ctx.variantName = alts[i][0];
            return [... converterForAlternative(ctx, alts[i][1], src, dest),
                    ... ((i < alts.length - 1)
                        ? [seq(`if (${dest} === void 0) `, ctx.block(() => loop(i + 1)))]
                        : [])];
        }
        return alts.length === 0 ? [] : loop(0);
    } else {
        ctx.variantName = void 0;
        return converterForAlternative(ctx, p, src, dest);
    }
}

function converterForAlternative(
    ctx: FunctionContext,
    p: M.Alternative,
    src: string,
    dest: string): Item[]
{
    if (p.label === M.$and) {
        const alts = p[0];
        function loop(i: number): Item[] {
            return (i < alts.length)
                ? converterFor(ctx, alts[i], src, () => loop(i + 1))
                : [ctx.buildCapturedCompound(dest)];
        }
        return alts.length === 0 ? [seq(`${dest} = ${src}`)] : loop(0);
    } else {
        return converterFor(ctx, p, src, simpleValue => {
            if (simpleValue === void 0) {
                return [ctx.buildCapturedCompound(dest)];
            } else if (ctx.variantName !== void 0) {
                return [ctx.withCapture('value',
                                        simpleValue,
                                        () => ctx.buildCapturedCompound(dest))];
            } else {
                return [`${dest} = ${simpleValue}`];
            }
        });
    }
}

function converterForTuple(ctx: FunctionContext,
                           ps: M.NamedPattern[],
                           src: string,
                           recordFields: boolean,
                           variablePattern: M.NamedSimplePattern | undefined,
                           k: () => Item[]): Item[]
{
    function loop(i: number): Item[] {
        if (i < ps.length) {
            return converterFor(ctx, ps[i], `${src}[${i}]`, () => loop(i + 1));
        } else {
            if (variablePattern === void 0) {
                return k();
            } else {
                const vN = ctx.gentemp(`Array<_val>`);
                return [ps.length > 0 ? `${vN} = ${src}.slice(${ps.length})` : `${vN} = ${src}`,
                        converterForArray(ctx, variablePattern, vN, false, k)];
            }
        }
    }

    const lengthCheck = variablePattern === void 0
        ? seq(` && ${src}.length === ${ps.length}`)
        : ((ps.length === 0) ? '' : seq(` && ${src}.length >= ${ps.length}`));

    return recordFields
        ? loop(0)
        : [seq(`if (_.Array.isArray(${src})`, lengthCheck, `) `, ctx.block(() => loop(0)))];
}

function converterForArray(ctx: FunctionContext,
                           arrayType: M.NamedSimplePattern,
                           src: string,
                           checkArray: boolean,
                           k: (dest: string) => Item[]): Item
{
    const postCheck = () => {
        const r = ctx.gentemp(
            `Array<`, typeFor(ctx.mod, M.unname(arrayType)), `> | undefined`);
        const v = ctx.gentempname();
        return [
            seq(`${r} = []`),
            seq(`for (const ${v} of ${src}) `, ctx.block(() => [
                ... converterFor(ctx, arrayType, v, vv => [`${r}.push(${vv})`, `continue`]),
                seq(`${r} = void 0`),
                seq(`break`)])),
            ctx.convertCapture(M.nameFor(arrayType), r, k)];
    };
    return (checkArray
        ? seq(`if (_.Array.isArray(${src})) `, ctx.block(postCheck))
        : block(... postCheck()));
}

function converterFor(
    ctx: FunctionContext,
    np: M.NamedPattern,
    src: string,
    ks: (dest: string | undefined) => Item[],
    recordFields = false): Item[]
{
    let p = M.unname(np);
    let maybeName = M.nameFor(np);

    if (M.isSimplePattern(p)) {
        const dest = ctx.gentemp(typeFor(ctx.mod, p), ` | undefined`);
        return [... converterForSimple(ctx, p, src, dest),
                ctx.convertCapture(maybeName, dest, ks)];
    } else {
        switch (p.label) {
            case M.$setof: {
                const setPattern = p[0];
                const r = ctx.gentemp(typeFor(ctx.mod, p), ` | undefined`);
                const v = ctx.gentempname();
                return [
                    seq(`if (_.Set.isSet<_ptr>(${src})) `, ctx.block(() => [
                        seq(`${r} = new _.KeyedSet()`),
                        seq(`for (const ${v} of ${src}) `, ctx.block(() => [
                            ... converterFor(ctx, setPattern, v, vv =>
                                [`${r}.add(${vv})`, `continue`]),
                            seq(`${r} = void 0`),
                            seq(`break`)])),
                        ctx.convertCapture(maybeName, r, ks)]))];
            }
            case M.$dictof: {
                const keyPattern = p[0];
                const valPattern = p[1];
                const r = ctx.gentemp(typeFor(ctx.mod, p), ` | undefined`);
                const v = ctx.gentempname();
                const k = ctx.gentempname();
                return [
                    seq(`if (_.Dictionary.isDictionary<_ptr>(${src})) `, ctx.block(() => [
                        seq(`${r} = new _.KeyedDictionary()`),
                        seq(`for (const [${k}, ${v}] of ${src}) `, ctx.block(() => [
                            ... converterFor(ctx, keyPattern, k, kk =>
                                converterFor(ctx, valPattern, v, vv =>
                                    [`${r}.set(${kk}, ${vv})`, `continue`])),
                            seq(`${r} = void 0`),
                            seq(`break`)])),
                        ctx.convertCapture(maybeName, r, ks)]))];
            }
            default: {
                const arrayType = M.simpleArray(p);
                if (arrayType === void 0) {
                    return converterForCompound(ctx, p, src, recordFields, () => ks(void 0));
                } else {
                    return [converterForArray(ctx, arrayType, src, !recordFields, ks)];
                }
            }
        }
    }
}

function converterForSimple(
    ctx: FunctionContext,
    p: M.SimplePattern,
    src: string,
    dest: string): Item[]
{
    switch (p.label) {
        case M.$atom: {
            let test: Item;
            switch (p[0]) {
                case M.$Boolean: test = `typeof ${src} === 'boolean'`; break;
                case M.$Float: test = `_.Float.isSingle(${src})`; break;
                case M.$Double: test =`_.Float.isDouble(${src})`; break;
                case M.$SignedInteger: test = `typeof ${src} === 'number'`; break;
                case M.$String: test = `typeof ${src} === 'string'`; break;
                case M.$ByteString: test = `_.Bytes.isBytes(${src})`; break;
                case M.$Symbol: test = `typeof ${src} === 'symbol'`; break;
            }
            return [seq(`${dest} = `, test, ` ? ${src} : void 0`)];
        }
        case M.$lit:
            return [`${dest} = _.is(${src}, ${ctx.mod.literal(p[0])}) ? ${ctx.mod.literal(p[0])} : void 0`];
        case M.$ref:
            return M.lookup(refPosition(p), p, ctx.mod.env,
                            (_p) => [`${dest} = to${p[1].description!}(${src})`],
                            (p) => converterForAlternative(ctx, p, src, dest),
                            (modId, modPath,_p) => {
                                ctx.mod.imports.add([modId, modPath]);
                                return [`${dest} = ${modId}.decode${p[1].description!}(${src})`];
                            });
        case M.$pointer:
            return [`${dest} = _toPtr(${src})`];
        default:
            ((_p: never) => {})(p);
            throw new Error("Unreachable");
    }
}

function converterForCompound(
    ctx: FunctionContext,
    p: M.CompoundPattern,
    src: string,
    recordFields: boolean,
    ks: () => Item[]): Item[]
{
    switch (p.label) {
        case M.$rec:
            return [seq(`if (_.Record.isRecord<_val, _.Tuple<_val>, _ptr>(${src})) `, ctx.block(() =>
                converterFor(ctx, p[0], `${src}.label`, () =>
                    converterFor(ctx, p[1], src, ks, true))))];
        case M.$tuple:
            return converterForTuple(ctx, p[0], src, recordFields, void 0, ks);
        case M.$tuple_STAR_:
            return converterForTuple(ctx, p[0], src, recordFields, p[1], ks);
        case M.$setof:
        case M.$dictof:
            throw new Error('Internal error: setof and dictof are handled in converterFor()');
        case M.$dict: {
            const entries = Array.from(p[0]);
            function loop(i: number): Item[] {
                if (i < entries.length) {
                    const [k, n] = entries[i];
                    const tmpSrc = ctx.gentemp();
                    return [seq(`if ((${tmpSrc} = ${src}.get(${ctx.mod.literal(k)})) !== void 0) `,
                                ctx.block(() =>
                                    converterFor(ctx, M.addNameIfAbsent(n, k), tmpSrc, () =>
                                        loop(i + 1))))];
                } else {
                    return ks();
                }
            }
            return [seq(`if (_.Dictionary.isDictionary<_ptr>(${src})) `, ctx.block(() => loop(0)))];
        }
        default:
            ((_p: never) => {})(p);
            throw new Error("Unreachable");
    }
}