syndicate-js/packages/core/src/runtime/dataspace.ts

/// SPDX-License-Identifier: GPL-3.0-or-later
/// SPDX-FileCopyrightText: Copyright © 2016-2023 Tony Garnock-Jones <tonyg@leastfixedpoint.com>

import { IdentityMap } from '@preserves/core';
import { Index } from './skeleton.js';
import { Actor, Assertion, Entity, Facet, Handle, LocalAction, Ref, Turn } from './actor.js';
import { Observe, toObserve } from '../gen/dataspace.js';
import * as P from '../gen/dataspacePatterns.js';

export type DataspaceOptions = {
    tracer?: (event: '+' | '-' | '!',
              assertion: Assertion,
              dataspace: Dataspace,
              is_significant: boolean) => void,
    dumpIndex?: boolean,
};

export class Dataspace implements Partial<Entity> {
    readonly options: DataspaceOptions;
    readonly index = new Index();
    readonly handleMap = new IdentityMap<Handle, Assertion>();

    constructor(options?: DataspaceOptions) {
        this.options = options ?? {};
    }

    assert(v: Assertion, handle: Handle): void {
        const is_new = this.index.addAssertion(v);
        this.options.tracer?.('+', v, this, is_new);
        if (is_new) {
            const o = toObserve(v);
            if (o !== void 0) {
                this.index.addObserver(o.pattern, o.observer);
            }
            if (this.options.dumpIndex ?? false) this.index.dump();
        }
        this.handleMap.set(handle, v);
    }

    retract(handle: Handle): void {
        const v = this.handleMap.get(handle);
        if (v === void 0) return;
        const is_last = this.index.removeAssertion(v);
        this.options.tracer?.('-', v, this, is_last);
        if (is_last) {
            const o = toObserve(v);
            if (o !== void 0) {
                this.index.removeObserver(o.pattern, o.observer);
            }
            if (this.options.dumpIndex ?? false) this.index.dump();
        }
    }

    message(v: Assertion): void {
        this.options.tracer?.('!', v, this, true);
        this.index.deliverMessage(v);
    }

    static boot(bootProc: (ds: Ref) => void, options?: DataspaceOptions): Actor {
        return Actor.boot(() => {
            Turn.activeFacet.preventInertCheck();
            const ds = Turn.active.ref(new Dataspace(options));
            bootProc(ds);
        });
    }
}

export function assertionObserver(f: (a: Assertion) => LocalAction | undefined): Partial<Entity> {
    const assertionMap = new IdentityMap<Handle, LocalAction>();
    return {
        assert(a: Assertion, h: Handle): void {
            const g = f(a) ?? null;
            if (g !== null) {
                assertionMap.set(h, g);
            }
        },
        retract(h: Handle): void {
            assertionMap.get(h)?.();
            assertionMap.delete(h);
        },
    };
}

export function assertionFacetObserver(f: (a: Assertion) => void, inertOk: boolean = true): Partial<Entity> {
    const facetMap = new IdentityMap<Handle, Facet>();
    return {
        assert(a: Assertion, h: Handle): void {
            facetMap.set(h, Turn.active.facet(() => {
                if (inertOk) Turn.activeFacet.preventInertCheck();
                f(a);
            }));
        },
        retract(h: Handle): void {
            const facet = facetMap.get(h);
            if (facet) Turn.active.stop(facet);
            facetMap.delete(h);
        },
    };
}

export function assertObserve(ds: Ref, pattern: P.Pattern, e: Partial<Entity>): Handle {
    return Turn.active.assert(ds, Observe({ pattern, observer: Turn.ref(e) }));
}