refactor: replace array-based expressions with typed class hierarchy

Replace the old Lisp-like array expression representation (["AND", ["PARAM", ...], ...]) with a class hierarchy rooted in an abstract Expression class (Literal, Parameter, Binary, Unary, FunctionCall, Conditional). This gives compile-time type safety to expression construction, evaluation, and pattern matching. Key changes: - New lib/common/expression.ts defines the class hierarchy with map/evaluate/toString methods - Rewrite parser as hand-rolled recursive descent, removing the parsimmon dependency - Extend Path with a colon separator to unify parameter identity and attributes into a single address space (e.g. "Device.WiFi.SSID.1.Name:writable"). The colon field tracks how many trailing segments are attribute qualifiers. PathSet rewritten with separate param/attr segment indexes - Flatten device attribute representation in the UI to colon-delimited keys mirroring the new path syntax
2026-03-12 14:58:20 -07:00
1 parent 75908e624f
commit 6f3ce6f7c8
@@ -0,0 +1,291 @@
+import {
+  Cursor,
+  parseExpression,
+  stringifyExpression,
+} from "./expression/parser.ts";
+import Path from "./path.ts";
+import { reduce } from "./expression/evaluate.ts";
+
+export type Value = string | number | boolean | null;
+
+export abstract class Expression {
+  private _string: string;
+
+  abstract map(fn: (e: Expression, i: number) => Expression): Expression;
+  abstract mapAsync(
+    fn: (e: Expression, i: number) => Promise<Expression>,
+  ): Promise<Expression>;
+
+  toString(): string {
+    if (!this._string) this._string = stringifyExpression(this);
+    return this._string;
+  }
+
+  evaluate<T extends Expression>(fn: (e: Expression) => T = (e) => e as T): T {
+    return fn(reduce(this.map((e) => e.evaluate(fn))));
+  }
+
+  async evaluateAsync<T extends Expression>(
+    fn: (e: Expression) => Promise<T>,
+  ): Promise<T> {
+    return await fn(
+      reduce(await this.mapAsync(async (e) => await e.evaluateAsync(fn))),
+    );
+  }
+
+  static parse(input: string): Expression {
+    const cursor = new Cursor(input);
+    const exp = parseExpression(cursor);
+    if (cursor.charCode) throw new Error("Unexpected character");
+    return exp;
+  }
+
+  static and(left: Expression, right: Expression): Expression {
+    // Flatten same-operator tree into operands
+    const operands: Expression[] = [];
+    const stack: Expression[] = [right, left];
+    while (stack.length) {
+      const e = stack.pop()!;
+      if (e instanceof Expression.Binary && e.operator === "AND")
+        stack.push(e.right, e.left);
+      else operands.push(e);
+    }
+
+    // Fold literals using three-valued AND logic
+    let folded: boolean | null = true;
+    let i = 0;
+    while (i < operands.length) {
+      const e = operands[i];
+      if (e instanceof Expression.Literal) {
+        operands.splice(i, 1);
+        if (e.value == null) folded = folded === false ? false : null;
+        else if (!e.value) return new Expression.Literal(false);
+        // truthy is identity for AND; discard
+      } else {
+        i++;
+      }
+    }
+
+    // Rebuild: folded value + remaining non-literal operands
+    if (!operands.length) return new Expression.Literal(folded);
+    let result = operands.reduce((a, b) => new Expression.Binary("AND", a, b));
+    if (folded === null)
+      result = new Expression.Binary(
+        "AND",
+        new Expression.Literal(null),
+        result,
+      );
+    return result;
+  }
+
+  static or(left: Expression, right: Expression): Expression {
+    // Flatten same-operator tree into operands
+    const operands: Expression[] = [];
+    const stack: Expression[] = [right, left];
+    while (stack.length) {
+      const e = stack.pop()!;
+      if (e instanceof Expression.Binary && e.operator === "OR")
+        stack.push(e.right, e.left);
+      else operands.push(e);
+    }
+
+    // Fold literals using three-valued OR logic
+    let folded: boolean | null = false;
+    let i = 0;
+    while (i < operands.length) {
+      const e = operands[i];
+      if (e instanceof Expression.Literal) {
+        operands.splice(i, 1);
+        if (e.value == null) folded = folded === true ? true : null;
+        else if (e.value) return new Expression.Literal(true);
+        // falsy is identity for OR; discard
+      } else {
+        i++;
+      }
+    }
+
+    // Rebuild: folded value + remaining non-literal operands
+    if (!operands.length) return new Expression.Literal(folded);
+    let result = operands.reduce((a, b) => new Expression.Binary("OR", a, b));
+    if (folded === null)
+      result = new Expression.Binary(
+        "OR",
+        new Expression.Literal(null),
+        result,
+      );
+    return result;
+  }
+}
+
+// eslint-disable-next-line @typescript-eslint/no-namespace
+export namespace Expression {
+  export class Literal extends Expression {
+    constructor(public readonly value: Value) {
+      super();
+    }
+
+    map(): Literal {
+      return this;
+    }
+
+    async mapAsync(): Promise<Literal> {
+      return this;
+    }
+  }
+
+  export class Parameter extends Expression {
+    constructor(public readonly path: Path) {
+      super();
+    }
+
+    map(): Parameter {
+      return this;
+    }
+
+    async mapAsync(): Promise<Parameter> {
+      return this;
+    }
+
+    toString(): string {
+      return this.path.toString();
+    }
+  }
+
+  export class Unary extends Expression {
+    constructor(
+      public readonly operator: string,
+      public readonly operand: Expression,
+    ) {
+      super();
+    }
+
+    map(fn: (e: Expression, i: number) => Expression): Unary {
+      const operand = fn(this.operand, 0);
+      if (operand === this.operand) return this;
+      return Reflect.construct(this.constructor, [this.operator, operand]);
+    }
+
+    async mapAsync(
+      fn: (e: Expression, i: number) => Promise<Expression>,
+    ): Promise<Unary> {
+      const operand = await fn(this.operand, 0);
+      if (operand === this.operand) return this;
+      return Reflect.construct(this.constructor, [this.operator, operand]);
+    }
+  }
+
+  export class Binary extends Expression {
+    constructor(
+      public readonly operator: string,
+      public readonly left: Expression,
+      public readonly right: Expression,
+    ) {
+      super();
+    }
+
+    map(fn: (e: Expression, i: number) => Expression): Binary {
+      const left = fn(this.left, 0);
+      const right = fn(this.right, 1);
+      if (left === this.left && right === this.right) return this;
+      return Reflect.construct(this.constructor, [this.operator, left, right]);
+    }
+
+    async mapAsync(
+      fn: (e: Expression, i: number) => Promise<Expression>,
+    ): Promise<Binary> {
+      const left = await fn(this.left, 0);
+      const right = await fn(this.right, 1);
+      if (left === this.left && right === this.right) return this;
+      return Reflect.construct(this.constructor, [this.operator, left, right]);
+    }
+  }
+
+  export class FunctionCall extends Expression {
+    constructor(
+      public readonly name: string,
+      public readonly args: Expression[],
+    ) {
+      super();
+    }
+
+    map(fn: (e: Expression, i: number) => Expression): FunctionCall {
+      const args = this.args.map(fn);
+      if (args.every((arg, i) => arg === this.args[i])) return this;
+      return new FunctionCall(this.name, args);
+    }
+
+    async mapAsync(
+      fn: (e: Expression, i: number) => Promise<Expression>,
+    ): Promise<FunctionCall> {
+      const args = await Promise.all(this.args.map(fn));
+      if (args.every((arg, i) => arg === this.args[i])) return this;
+      return new FunctionCall(this.name, args);
+    }
+  }
+
+  export class Conditional extends Expression {
+    constructor(
+      public readonly condition: Expression,
+      public readonly then: Expression,
+      public readonly otherwise: Expression,
+    ) {
+      super();
+    }
+
+    map(fn: (e: Expression, i: number) => Expression): Conditional {
+      const condition = fn(this.condition, 0);
+      const then = fn(this.then, 1);
+      const otherwise = fn(this.otherwise, 2);
+      if (
+        condition === this.condition &&
+        then === this.then &&
+        otherwise === this.otherwise
+      )
+        return this;
+      return new Conditional(condition, then, otherwise);
+    }
+
+    async mapAsync(
+      fn: (e: Expression, i: number) => Promise<Expression>,
+    ): Promise<Conditional> {
+      const condition = await fn(this.condition, 0);
+      const then = await fn(this.then, 1);
+      const otherwise = await fn(this.otherwise, 2);
+      if (
+        condition === this.condition &&
+        then === this.then &&
+        otherwise === this.otherwise
+      )
+        return this;
+      return new Conditional(condition, then, otherwise);
+    }
+  }
+}
+
+export function extractPaths(exp: Expression): Path[] {
+  if (exp instanceof Expression.Parameter) return [exp.path];
+  const paths: Path[] = [];
+  exp.map((e) => {
+    if (e instanceof Expression.Parameter) paths.push(e.path);
+    else paths.push(...extractPaths(e));
+    return e;
+  });
+  return paths;
+}
+
+export function parseList(input: string): Expression[] {
+  const CHAR_COMMA = 44;
+  const res: Expression[] = [];
+  const cursor = new Cursor(input);
+  cursor.skipwhitespace();
+  if (!cursor.charCode) return res;
+  res.push(parseExpression(cursor));
+  while (cursor.charCode === CHAR_COMMA) {
+    cursor.step();
+    res.push(parseExpression(cursor));
+  }
+  if (cursor.charCode) throw new Error("Unexpected character");
+  return res;
+}
+
+export default Expression;