import * as ts from "typescript";
import type { LintRule, LintContext, LintDiagnostic } from "../rule";

/**
 * EVL002: Control Flow Wrapping Resources
 *
 * Resource constructors (NewExpression) must not appear inside
 * control flow statements (if, for, while, switch, try, etc.).
 * Resources must be unconditionally declared.
 */

const CONTROL_FLOW_KINDS = new Set([
  ts.SyntaxKind.IfStatement,
  ts.SyntaxKind.ForStatement,
  ts.SyntaxKind.ForInStatement,
  ts.SyntaxKind.ForOfStatement,
  ts.SyntaxKind.WhileStatement,
  ts.SyntaxKind.DoStatement,
  ts.SyntaxKind.SwitchStatement,
  ts.SyntaxKind.TryStatement,
]);

/**
 * JS built-ins that are never a cloud resource. The rule guards resource
 * declarations, so a guard clause like `if (bad) throw new Error(...)` — or a
 * local `new Map()`/`new Set()` — must not be flagged as a control-flow resource.
 */
const NON_RESOURCE_CONSTRUCTORS = new Set([
  "Error", "TypeError", "RangeError", "SyntaxError", "ReferenceError",
  "EvalError", "URIError", "AggregateError",
  "Map", "Set", "WeakMap", "WeakSet", "WeakRef", "Date", "RegExp", "Promise",
  "Array", "Object", "String", "Number", "Boolean",
]);

/** The constructor identifier of a `new X(...)`, if it's a bare name. */
function constructorName(node: ts.NewExpression): string | undefined {
  return ts.isIdentifier(node.expression) ? node.expression.text : undefined;
}

function isInsideControlFlow(node: ts.Node): boolean {
  let current = node.parent;
  while (current) {
    if (CONTROL_FLOW_KINDS.has(current.kind)) return true;
    current = current.parent;
  }
  return false;
}

function checkNode(node: ts.Node, context: LintContext, diagnostics: LintDiagnostic[]): void {
  if (ts.isNewExpression(node) && !NON_RESOURCE_CONSTRUCTORS.has(constructorName(node) ?? "")) {
    if (isInsideControlFlow(node)) {
      const { line, character } = context.sourceFile.getLineAndCharacterOfPosition(
        node.getStart(context.sourceFile),
      );
      diagnostics.push({
        file: context.filePath,
        line: line + 1,
        column: character + 1,
        ruleId: "EVL002",
        severity: "error",
        message: "Resource constructor inside control flow — resources must be unconditionally declared",
      });
    }
  }

  ts.forEachChild(node, (child) => checkNode(child, context, diagnostics));
}

export const evl002ControlFlowResourceRule: LintRule = {
  id: "EVL002",
  severity: "error",
  category: "correctness",
  description: "Resource constructors must not appear inside control flow statements",
  check(context: LintContext): LintDiagnostic[] {
    const diagnostics: LintDiagnostic[] = [];
    checkNode(context.sourceFile, context, diagnostics);
    return diagnostics;
  },
};