import type { CloudFormationStackArtifact } from "aws-cdk-lib/cx-api";
import type { FormatStream } from "@aws-cdk/cloudformation-diff";

export async function diff(
  stack: CloudFormationStackArtifact,
  oldTemplate: any
) {
  const { diffTemplate, formatDifferences, TemplateDiff } = await import(
    "@aws-cdk/cloudformation-diff"
  );

  // Generate diff
  const diff = diffTemplate(oldTemplate, stack.template);
  if (diff.isEmpty) {
    return { count: 0 };
  }

  // Only display resource and output changes
  // @ts-ignore
  diff.iamChanges = { hasChanges: false };
  // @ts-ignore
  diff.securityGroupChanges = { hasChanges: false };
  // @ts-ignore
  diff.awsTemplateFormatVersion = false;
  // @ts-ignore
  diff.transform = false;
  // @ts-ignore
  diff.description = false;
  // @ts-ignore
  diff.parameters = { differenceCount: 0 };
  // @ts-ignore
  diff.metadata = { differenceCount: 0 };
  // @ts-ignore
  diff.mappings = { differenceCount: 0 };
  // @ts-ignore
  diff.conditions = { differenceCount: 0 };
  // @ts-ignore
  diff.unknown = { differenceCount: 0 };

  // Filter out SST internal diffs
  // @ts-ignore
  delete diff.outputs.diffs?.["SSTMetadata"];

  // Format diff
  const output: string[] = [];
  const stream = {
    write(chunk: string) {
      output.push(`   ${chunk}`);
    },
  } as FormatStream;
  const pathMap = await buildLogicalToPathMap(stack);
  formatDifferences(stream, diff, pathMap);

  // Remove trailing newline
  while (true) {
    if (output[output.length - 1]?.match(/^\s*$/)) {
      output.pop();
    } else {
      break;
    }
  }

  return {
    count: diff.outputs.differenceCount + diff.resources.differenceCount,
    diff: output.join(""),
  };
}

async function buildLogicalToPathMap(stack: CloudFormationStackArtifact) {
  const { ArtifactMetadataEntryType } = await import(
    "@aws-cdk/cloud-assembly-schema"
  );
  const map: { [id: string]: string } = {};
  for (const md of stack.findMetadataByType(
    ArtifactMetadataEntryType.LOGICAL_ID
  )) {
    map[md.data as string] = md.path;
  }
  return map;
}