feat: implementing permission checker

packages/runtime/package.json

@@ -29,6 +29,10 @@
             "types": "./enhancements/index.d.ts",
             "default": "./enhancements/index.js"
         },
+        "./constraint-solver": {
+            "types": "./constraint-solver.d.ts",
+            "default": "./constraint-solver.js"
+        },
         "./zod": {
             "types": "./zod/index.d.ts",
             "default": "./zod/index.js"
@@ -79,12 +83,14 @@
         "decimal.js": "^10.4.2",
         "deepcopy": "^2.1.0",
         "deepmerge": "^4.3.1",
+        "logic-solver": "^2.0.1",
         "lower-case-first": "^2.0.2",
         "pluralize": "^8.0.0",
         "safe-json-stringify": "^1.2.0",
         "semver": "^7.5.2",
         "superjson": "^1.11.0",
         "tiny-invariant": "^1.3.1",
+        "ts-pattern": "^4.3.0",
         "tslib": "^2.4.1",
         "upper-case-first": "^2.0.2",
         "uuid": "^9.0.0",

packages/runtime/src/enhancements/policy/constraint-solver.ts

@@ -0,0 +1,219 @@
+import Logic from 'logic-solver';
+import { match } from 'ts-pattern';
+import type {
+    CheckerConstraint,
+    ComparisonConstraint,
+    ComparisonTerm,
+    LogicalConstraint,
+    ValueConstraint,
+    VariableConstraint,
+} from '../types';
+
+/**
+ * A boolean constraint solver based on `logic-solver`. Only boolean and integer types are supported.
+ */
+export class ConstraintSolver {
+    // a table for internalizing string literals
+    private stringTable: string[] = [];
+
+    // a map for storing variable names and their corresponding formulas
+    private variables: Map<string, Logic.Formula> = new Map<string, Logic.Formula>();
+
+    /**
+     * Check the satisfiability of the given constraint.
+     */
+    checkSat(constraint: CheckerConstraint): boolean {
+        // reset state
+        this.stringTable = [];
+        this.variables = new Map<string, Logic.Formula>();
+
+        // convert the constraint to a "logic-solver" formula
+        const formula = this.buildFormula(constraint);
+
+        // solve the formula
+        const solver = new Logic.Solver();
+        solver.require(formula);
+
+        // DEBUG:
+        // const solution = solver.solve();
+        // if (solution) {
+        //     console.log('Solution:');
+        //     this.variables.forEach((v, k) => console.log(`\t${k}=${solution?.evaluate(v)}`));
+        // } else {
+        //     console.log('No solution');
+        // }
+
+        return !!solver.solve();
+    }
+
+    private buildFormula(constraint: CheckerConstraint): Logic.Formula {
+        return match(constraint)
+            .when(
+                (c): c is ValueConstraint => c.kind === 'value',
+                (c) => this.buildValueFormula(c)
+            )
+            .when(
+                (c): c is VariableConstraint => c.kind === 'variable',
+                (c) => this.buildVariableFormula(c)
+            )
+            .when(
+                (c): c is ComparisonConstraint => ['eq', 'ne', 'gt', 'gte', 'lt', 'lte'].includes(c.kind),
+                (c) => this.buildComparisonFormula(c)
+            )
+            .when(
+                (c): c is LogicalConstraint => ['and', 'or', 'not'].includes(c.kind),
+                (c) => this.buildLogicalFormula(c)
+            )
+            .otherwise(() => {
+                throw new Error(`Unsupported constraint format: ${JSON.stringify(constraint)}`);
+            });
+    }
+
+    private buildLogicalFormula(constraint: LogicalConstraint) {
+        return match(constraint.kind)
+            .with('and', () => this.buildAndFormula(constraint))
+            .with('or', () => this.buildOrFormula(constraint))
+            .with('not', () => this.buildNotFormula(constraint))
+            .exhaustive();
+    }
+
+    private buildAndFormula(constraint: LogicalConstraint): Logic.Formula {
+        if (constraint.children.some((c) => this.isFalse(c))) {
+            // short-circuit
+            return Logic.FALSE;
+        }
+        return Logic.and(...constraint.children.map((c) => this.buildFormula(c)));
+    }
+
+    private buildOrFormula(constraint: LogicalConstraint): Logic.Formula {
+        if (constraint.children.some((c) => this.isTrue(c))) {
+            // short-circuit
+            return Logic.TRUE;
+        }
+        return Logic.or(...constraint.children.map((c) => this.buildFormula(c)));
+    }
+
+    private buildNotFormula(constraint: LogicalConstraint) {
+        if (constraint.children.length !== 1) {
+            throw new Error('"not" constraint must have exactly one child');
+        }
+        return Logic.not(this.buildFormula(constraint.children[0]));
+    }
+
+    private isTrue(constraint: CheckerConstraint): unknown {
+        return constraint.kind === 'value' && constraint.value === true;
+    }
+
+    private isFalse(constraint: CheckerConstraint): unknown {
+        return constraint.kind === 'value' && constraint.value === false;
+    }
+
+    private buildComparisonFormula(constraint: ComparisonConstraint) {
+        if (constraint.left.kind === 'value' && constraint.right.kind === 'value') {
+            // constant comparison
+            const left: ValueConstraint = constraint.left;
+            const right: ValueConstraint = constraint.right;
+            return match(constraint.kind)
+                .with('eq', () => (left.value === right.value ? Logic.TRUE : Logic.FALSE))
+                .with('ne', () => (left.value !== right.value ? Logic.TRUE : Logic.FALSE))
+                .with('gt', () => (left.value > right.value ? Logic.TRUE : Logic.FALSE))
+                .with('gte', () => (left.value >= right.value ? Logic.TRUE : Logic.FALSE))
+                .with('lt', () => (left.value < right.value ? Logic.TRUE : Logic.FALSE))
+                .with('lte', () => (left.value <= right.value ? Logic.TRUE : Logic.FALSE))
+                .exhaustive();
+        }
+
+        return match(constraint.kind)
+            .with('eq', () => this.transformEquality(constraint.left, constraint.right))
+            .with('ne', () => this.transformInequality(constraint.left, constraint.right))
+            .with('gt', () =>
+                this.transformComparison(constraint.left, constraint.right, (l, r) => Logic.greaterThan(l, r))
+            )
+            .with('gte', () =>
+                this.transformComparison(constraint.left, constraint.right, (l, r) => Logic.greaterThanOrEqual(l, r))
+            )
+            .with('lt', () =>
+                this.transformComparison(constraint.left, constraint.right, (l, r) => Logic.lessThan(l, r))
+            )
+            .with('lte', () =>
+                this.transformComparison(constraint.left, constraint.right, (l, r) => Logic.lessThanOrEqual(l, r))
+            )
+            .exhaustive();
+    }
+
+    private buildVariableFormula(constraint: VariableConstraint) {
+        return (
+            match(constraint.type)
+                .with('boolean', () => this.booleanVariable(constraint.name))
+                .with('number', () => this.intVariable(constraint.name))
+                // strings are internalized and represented by their indices
+                .with('string', () => this.intVariable(constraint.name))
+                .exhaustive()
+        );
+    }
+
+    private buildValueFormula(constraint: ValueConstraint) {
+        return match(constraint.value)
+            .when(
+                (v): v is boolean => typeof v === 'boolean',
+                (v) => (v === true ? Logic.TRUE : Logic.FALSE)
+            )
+            .when(
+                (v): v is number => typeof v === 'number',
+                (v) => Logic.constantBits(v)
+            )
+            .when(
+                (v): v is string => typeof v === 'string',
+                (v) => {
+                    // internalize the string and use its index as formula representation
+                    const index = this.stringTable.indexOf(v);
+                    if (index === -1) {
+                        this.stringTable.push(v);
+                        return Logic.constantBits(this.stringTable.length - 1);
+                    } else {
+                        return Logic.constantBits(index);
+                    }
+                }
+            )
+            .exhaustive();
+    }
+
+    private booleanVariable(name: string) {
+        this.variables.set(name, name);
+        return name;
+    }
+
+    private intVariable(name: string) {
+        const r = Logic.variableBits(name, 32);
+        this.variables.set(name, r);
+        return r;
+    }
+
+    private transformEquality(left: ComparisonTerm, right: ComparisonTerm) {
+        if (left.type !== right.type) {
+            throw new Error(`Type mismatch in equality constraint: ${JSON.stringify(left)}, ${JSON.stringify(right)}`);
+        }
+
+        const leftFormula = this.buildFormula(left);
+        const rightFormula = this.buildFormula(right);
+        if (left.type === 'boolean' && right.type === 'boolean') {
+            // logical equivalence
+            return Logic.equiv(leftFormula, rightFormula);
+        } else {
+            // integer equality
+            return Logic.equalBits(leftFormula, rightFormula);
+        }
+    }
+
+    private transformInequality(left: ComparisonTerm, right: ComparisonTerm) {
+        return Logic.not(this.transformEquality(left, right));
+    }
+
+    private transformComparison(
+        left: ComparisonTerm,
+        right: ComparisonTerm,
+        func: (left: Logic.Formula, right: Logic.Formula) => Logic.Formula
+    ) {
+        return func(this.buildFormula(left), this.buildFormula(right));
+    }
+}

packages/runtime/src/enhancements/policy/handler.ts

@@ -2,6 +2,7 @@
 
 import { lowerCaseFirst } from 'lower-case-first';
 import invariant from 'tiny-invariant';
+import { P, match } from 'ts-pattern';
 import { upperCaseFirst } from 'upper-case-first';
 import { fromZodError } from 'zod-validation-error';
 import { CrudFailureReason } from '../../constants';
@@ -16,13 +17,15 @@ import {
     type FieldInfo,
     type ModelMeta,
 } from '../../cross';
-import { PolicyOperationKind, type CrudContract, type DbClientContract } from '../../types';
+import { PolicyCrudKind, PolicyOperationKind, type CrudContract, type DbClientContract } from '../../types';
 import type { EnhancementContext, InternalEnhancementOptions } from '../create-enhancement';
 import { Logger } from '../logger';
 import { createDeferredPromise, createFluentPromise } from '../promise';
 import { PrismaProxyHandler } from '../proxy';
 import { QueryUtils } from '../query-utils';
+import type { CheckerConstraint } from '../types';
 import { clone, formatObject, isUnsafeMutate, prismaClientValidationError } from '../utils';
+import { ConstraintSolver } from './constraint-solver';
 import { PolicyUtil } from './policy-utils';
 
 // a record for post-write policy check
@@ -1436,6 +1439,96 @@ export class PolicyProxyHandler<DbClient extends DbClientContract> implements Pr
 
     //#endregion
 
+    //#region Check
+
+    /**
+     * Checks if the given operation is possibly allowed by the policy, without querying the database.
+     * @param operation The CRUD operation.
+     * @param fieldValues Extra field value filters to be combined with the policy constraints.
+     */
+    async check(
+        operation: PolicyCrudKind,
+        fieldValues?: Record<string, number | string | boolean | null>
+    ): Promise<boolean> {
+        return createDeferredPromise(() => this.doCheck(operation, fieldValues));
+    }
+
+    private async doCheck(operation: PolicyCrudKind, fieldValues?: Record<string, number | string | boolean | null>) {
+        let constraint = this.policyUtils.getCheckerConstraint(this.model, operation);
+        if (typeof constraint === 'boolean') {
+            return constraint;
+        }
+
+        if (fieldValues) {
+            // combine runtime filters with generated constraints
+
+            const extraConstraints: CheckerConstraint[] = [];
+            for (const [field, value] of Object.entries(fieldValues)) {
+                if (value === undefined) {
+                    continue;
+                }
+
+                if (value === null) {
+                    throw new Error(`Using "null" as filter value is not supported yet`);
+                }
+
+                const fieldInfo = requireField(this.modelMeta, this.model, field);
+
+                // relation and array fields are not supported
+                if (fieldInfo.isDataModel || fieldInfo.isArray) {
+                    throw new Error(
+                        `Providing filter for field "${field}" is not supported. Only scalar fields are allowed.`
+                    );
+                }
+
+                // map field type to constraint type
+                const fieldType = match<string, 'number' | 'string' | 'boolean'>(fieldInfo.type)
+                    .with(P.union('Int', 'BigInt', 'Float', 'Decimal'), () => 'number')
+                    .with('String', () => 'string')
+                    .with('Boolean', () => 'boolean')
+                    .otherwise(() => {
+                        throw new Error(
+                            `Providing filter for field "${field}" is not supported. Only number, string, and boolean fields are allowed.`
+                        );
+                    });
+
+                // check value type
+                const valueType = typeof value;
+                if (valueType !== 'number' && valueType !== 'string' && valueType !== 'boolean') {
+                    throw new Error(
+                        `Invalid value type for field "${field}". Only number, string or boolean is allowed.`
+                    );
+                }
+
+                if (fieldType !== valueType) {
+                    throw new Error(`Invalid value type for field "${field}". Expected "${fieldType}".`);
+                }
+
+                // check number validity
+                if (typeof value === 'number' && (!Number.isInteger(value) || value < 0)) {
+                    throw new Error(`Invalid value for field "${field}". Only non-negative integers are allowed.`);
+                }
+
+                // build a constraint
+                extraConstraints.push({
+                    kind: 'eq',
+                    left: { kind: 'variable', name: field, type: fieldType },
+                    right: { kind: 'value', value, type: fieldType },
+                });
+            }
+
+            if (extraConstraints.length > 0) {
+                // combine the constraints
+                constraint = { kind: 'and', children: [constraint, ...extraConstraints] };
+            }
+        }
+
+        // check satisfiability
+        return new ConstraintSolver().checkSat(constraint);
+    }
+
+    //#endregion
+
     //#region Utils
 
     private get shouldLogQuery() {