import * as fs from "fs";
import * as path from "path";

import * as actionsUtil from "./actions-util";
import type { PullRequestBranches } from "./actions-util";
import { getGitHubVersion } from "./api-client";
import type { CodeQL } from "./codeql";
import { Feature, FeatureEnablement } from "./feature-flags";
import { Logger } from "./logging";
import { GitHubVariant, satisfiesGHESVersion } from "./util";

/**
 * Check if the action should perform diff-informed analysis.
 */
export async function shouldPerformDiffInformedAnalysis(
  codeql: CodeQL,
  features: FeatureEnablement,
  logger: Logger,
): Promise<boolean> {
  return (
    (await getDiffInformedAnalysisBranches(codeql, features, logger)) !==
    undefined
  );
}

/**
 * Get the branches to use for diff-informed analysis.
 *
 * @returns If the action should perform diff-informed analysis, return
 * the base and head branches that should be used to compute the diff ranges.
 * Otherwise return `undefined`.
 */
export async function getDiffInformedAnalysisBranches(
  codeql: CodeQL,
  features: FeatureEnablement,
  logger: Logger,
): Promise<PullRequestBranches | undefined> {
  if (!(await features.getValue(Feature.DiffInformedQueries, codeql))) {
    return undefined;
  }

  const gitHubVersion = await getGitHubVersion();
  if (
    gitHubVersion.type === GitHubVariant.GHES &&
    satisfiesGHESVersion(gitHubVersion.version, "<3.19", true)
  ) {
    return undefined;
  }

  const branches = actionsUtil.getPullRequestBranches();
  if (!branches) {
    logger.info(
      "Not performing diff-informed analysis " +
        "because we are not analyzing a pull request.",
    );
  }
  return branches;
}

export interface DiffThunkRange {
  path: string;
  startLine: number;
  endLine: number;
}

function getDiffRangesJsonFilePath(): string {
  return path.join(actionsUtil.getTemporaryDirectory(), "pr-diff-range.json");
}

export function writeDiffRangesJsonFile(
  logger: Logger,
  ranges: DiffThunkRange[],
): void {
  const jsonContents = JSON.stringify(ranges, null, 2);
  const jsonFilePath = getDiffRangesJsonFilePath();
  fs.writeFileSync(jsonFilePath, jsonContents);
  logger.debug(
    `Wrote pr-diff-range JSON file to ${jsonFilePath}:\n${jsonContents}`,
  );
}

export function readDiffRangesJsonFile(
  logger: Logger,
): DiffThunkRange[] | undefined {
  const jsonFilePath = getDiffRangesJsonFilePath();
  if (!fs.existsSync(jsonFilePath)) {
    logger.debug(`Diff ranges JSON file does not exist at ${jsonFilePath}`);
    return undefined;
  }
  const jsonContents = fs.readFileSync(jsonFilePath, "utf8");
  logger.debug(
    `Read pr-diff-range JSON file from ${jsonFilePath}:\n${jsonContents}`,
  );
  return JSON.parse(jsonContents) as DiffThunkRange[];
}