/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

const exec = require("@actions/exec");
const fs = require("fs");
const path = require("path");
const { Pr } = require("./pr");
const { ReviewersForLabel } = require("./reviewersForLabel");
const { BOT_NAME, PR_STATE_DIR } = require("./constants");

function getPrFileName(prNumber) {
  return `pr-${prNumber}.json`.toLowerCase();
}

function getReviewersForLabelFileName(label) {
  return `reviewers-for-label-${label}.json`.toLowerCase();
}

async function commitStateToRepo() {
  try {
    await exec.exec("git pull origin pr-bot-state");
  } catch (err) {
    console.log(
      `Unable to get most recent repo contents, commit may fail: ${err}`
    );
  }
  // Print changes for observability
  await exec.exec("git status", [], { ignoreReturnCode: true });
  await exec.exec("git add -A state");
  const changes = await exec.exec(
    "git diff --quiet --cached origin/pr-bot-state state",
    [],
    { ignoreReturnCode: true }
  );
  if (changes == 1) {
    await exec.exec(`git commit -m "Updating config from bot" --allow-empty`);
    await exec.exec("git push origin pr-bot-state");
  } else {
    console.log(
      "Skipping updating state branch since there are no changes to commit"
    );
  }
}

export class PersistentState {
  private switchedBranch = false;

  // Returns a Pr object representing the current saved state of the pr.
  async getPrState(prNumber: number): Promise<typeof Pr> {
    var fileName = getPrFileName(prNumber);
    return new Pr(await this.getState(fileName, PR_STATE_DIR));
  }

  // Writes a Pr object representing the current saved state of the pr to persistent storage.
  async writePrState(prNumber: number, newState: any) {
    var fileName = getPrFileName(prNumber);
    await this.writeState(fileName, PR_STATE_DIR, new Pr(newState));
  }

  // Returns a ReviewersForLabel object representing the current saved state of which reviewers have reviewed recently.
  async getReviewersForLabelState(
    label: string
  ): Promise<typeof ReviewersForLabel> {
    var fileName = getReviewersForLabelFileName(label);
    return new ReviewersForLabel(label, await this.getState(fileName, "state"));
  }

  // Writes a ReviewersForLabel object representing the current saved state of which reviewers have reviewed recently.
  async writeReviewersForLabelState(label: string, newState: any) {
    var fileName = getReviewersForLabelFileName(label);
    await this.writeState(
      fileName,
      "state",
      new ReviewersForLabel(label, newState)
    );
  }

  // Deletes up to maxToDelete state files for PRs that are no longer open, starting from the oldest PRs.
  async deleteStalePrStates(
    openPulls: any[],
    maxToDelete: number = 100
  ): Promise<number> {
    if (openPulls.length === 0) {
      return 0;
    }
    await this.ensureCorrectBranch();
    if (!fs.existsSync(PR_STATE_DIR)) {
      return 0;
    }
    const openPrSet = new Set(openPulls.map((p) => p.number));
    const files = fs.readdirSync(PR_STATE_DIR);
    const stalePrs: { prNumber: number; filePath: string }[] = [];

    for (const file of files) {
      const match = file.match(/^pr-(\d+)\.json$/);
      if (match) {
        const prNumber = parseInt(match[1], 10);
        if (!openPrSet.has(prNumber)) {
          stalePrs.push({
            prNumber,
            filePath: path.join(PR_STATE_DIR, file),
          });
        }
      }
    }

    // Sort by PR number ascending so the oldest PRs are deleted first
    stalePrs.sort((a, b) => a.prNumber - b.prNumber);

    const prsToDelete = stalePrs.slice(0, maxToDelete);
    for (const pr of prsToDelete) {
      fs.unlinkSync(pr.filePath);
    }

    if (prsToDelete.length > 0) {
      console.log(
        `Deleted ${prsToDelete.length} stale PR state files (oldest: PR ${
          prsToDelete[0].prNumber
        }, newest: PR ${prsToDelete[prsToDelete.length - 1].prNumber})`
      );
      await commitStateToRepo();
    }

    return prsToDelete.length;
  }

  private async getState(fileName, baseDirectory) {
    await this.ensureCorrectBranch();
    fileName = path.join(baseDirectory, fileName);
    if (!fs.existsSync(fileName)) {
      return null;
    }
    return JSON.parse(fs.readFileSync(fileName, { encoding: "utf-8" }));
  }

  private async writeState(fileName, baseDirectory, state) {
    await this.ensureCorrectBranch();
    fileName = path.join(baseDirectory, fileName);
    if (!fs.existsSync(baseDirectory)) {
      fs.mkdirSync(baseDirectory, { recursive: true });
    }
    fs.writeFileSync(fileName, JSON.stringify(state, null, 2), {
      encoding: "utf-8",
    });
    await commitStateToRepo();
  }

  private async ensureCorrectBranch() {
    if (this.switchedBranch) {
      return;
    }
    console.log(
      "Switching to branch pr-bot-state for reading/storing persistent state between runs"
    );
    try {
      await exec.exec(`git config user.name ${BOT_NAME}`);
      await exec.exec(`git config user.email ${BOT_NAME}@github.com`);
      await exec.exec("git config pull.rebase false");
      await exec.exec("git fetch origin pr-bot-state --depth=1");
      await exec.exec("git checkout pr-bot-state");
    } catch {
      console.log(
        "Couldnt find branch pr-bot-state in origin, trying to create it"
      );
      await exec.exec("git checkout -b pr-bot-state");
      // Ensure that if we've created or just checked out the branch that we can also push to it
      await exec.exec("git push origin pr-bot-state");
    }
    this.switchedBranch = true;
  }
}