feat: core grammar, discovery and renderer; Postgres dialect; conformance suite

packages/core/src/read.ts

@@ -0,0 +1,52 @@
+import type { Dialect, Tx } from './dialect.js';
+import { notFound } from './errors.js';
+import { parseRead } from './grammar/read.js';
+import type { Limits, RestRequest, RestResponse } from './options.js';
+import type { Filter, ReadPlan } from './plan.js';
+import type { Resource } from './resources.js';
+import { typed } from './grammar/values.js';
+
+function decode(row: Record<string, unknown>): unknown {
+    const r = row.r;
+    return typeof r === 'string' ? JSON.parse(r) : r;
+}
+
+async function total(db: Dialect, tx: Tx, plan: ReadPlan, scope: (r: Resource) => Filter[]): Promise<number | null> {
+    if (plan.count === 'none') return null;
+    const stmt = db.renderer.count(plan, db.renderer.context(scope));
+    if (plan.count === 'estimated' && db.capabilities.estimatedCount && db.estimate) {
+        const n = await db.estimate(tx, stmt.sql, stmt.params);
+        if (n !== null) return n;
+    }
+    const [row] = await tx.query(stmt.sql, stmt.params);
+    return Number(row?.n ?? 0);
+}
+
+export function keyFilter(resource: Resource, id: string): Filter {
+    if (resource.key.length !== 1) throw notFound();
+    const column = resource.all.get(resource.key[0])!;
+    let value;
+    try { value = typed(id, column.type, column.name); } catch { throw notFound(); }
+    return { kind: 'cmp', path: { relations: [], column: column.name }, op: 'eq', negate: false, value };
+}
+
+/** GET on a collection, or on one row when id is given. */
+export async function readRows(db: Dialect, tx: Tx, resource: Resource, request: RestRequest<unknown>, limits: Limits,
+    scope: (r: Resource) => Filter[], id?: string): Promise<RestResponse> {
+    const plan = parseRead(resource, request.query, limits);
+    if (id !== undefined) {
+        plan.where.unshift(keyFilter(resource, id));
+        plan.limit = 1;
+        plan.offset = 0;
+        plan.count = 'none';
+    }
+    const stmt = db.renderer.read(plan, db.renderer.context(scope));
+    const rows = (await tx.query(stmt.sql, stmt.params)).map(decode);
+    if (id !== undefined) {
+        if (rows.length === 0) throw notFound();
+        return { status: 200, headers: {}, body: rows[0] };
+    }
+    const n = await total(db, tx, plan, scope);
+    const range = rows.length ? `${plan.offset}-${plan.offset + rows.length - 1}` : '*';
+    return { status: 200, headers: { 'content-range': `${range}/${n ?? '*'}` }, body: rows };
+}