/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

import {CompilerError} from '../CompilerError';
import {
  GeneratedSource,
  HIRFunction,
  Identifier,
  IdentifierId,
  SourceLocation,
} from './HIR';
import {printPlace} from './PrintHIR';
import {
  eachInstructionLValue,
  eachInstructionValueOperand,
  eachTerminalOperand,
} from './visitors';

/*
 * Validation pass to check that there is a 1:1 mapping between Identifier objects and IdentifierIds,
 * ie there can only be one Identifier instance per IdentifierId.
 */
export function assertConsistentIdentifiers(fn: HIRFunction): void {
  const identifiers: Identifiers = new Map();
  const assignments: Set<IdentifierId> = new Set();
  for (const [, block] of fn.body.blocks) {
    for (const phi of block.phis) {
      validate(identifiers, phi.place.identifier);
      for (const [, operand] of phi.operands) {
        validate(identifiers, operand.identifier);
      }
    }
    for (const instr of block.instructions) {
      CompilerError.invariant(instr.lvalue.identifier.name === null, {
        reason: `Expected all lvalues to be temporaries`,
        description: `Found named lvalue \`${instr.lvalue.identifier.name}\``,
        loc: instr.lvalue.loc,
      });
      CompilerError.invariant(!assignments.has(instr.lvalue.identifier.id), {
        reason: `Expected lvalues to be assigned exactly once`,
        description: `Found duplicate assignment of '${printPlace(
          instr.lvalue,
        )}'`,
        loc: instr.lvalue.loc,
      });
      assignments.add(instr.lvalue.identifier.id);
      for (const operand of eachInstructionLValue(instr)) {
        validate(identifiers, operand.identifier, operand.loc);
      }
      for (const operand of eachInstructionValueOperand(instr.value)) {
        validate(identifiers, operand.identifier, operand.loc);
      }
    }
    for (const operand of eachTerminalOperand(block.terminal)) {
      validate(identifiers, operand.identifier, operand.loc);
    }
  }
}

type Identifiers = Map<IdentifierId, Identifier>;

function validate(
  identifiers: Identifiers,
  identifier: Identifier,
  loc: SourceLocation | null = null,
): void {
  const previous = identifiers.get(identifier.id);
  if (previous === undefined) {
    identifiers.set(identifier.id, identifier);
  } else {
    CompilerError.invariant(identifier === previous, {
      reason: `Duplicate identifier object`,
      description: `Found duplicate identifier object for id ${identifier.id}`,
      loc: loc ?? GeneratedSource,
    });
  }
}