/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

/*
 * This action handles the life cycle of add-on based studies. Currently that
 * means installing the add-on the first time the recipe applies to this
 * client, updating the add-on to new versions if the recipe changes, and
 * uninstalling them when the recipe no longer applies.
 */

import { BaseStudyAction } from "resource://normandy/actions/BaseStudyAction.sys.mjs";

const lazy = {};

ChromeUtils.defineESModuleGetters(lazy, {
  ActionSchemas: "resource://normandy/actions/schemas/index.sys.mjs",
  AddonManager: "resource://gre/modules/AddonManager.sys.mjs",
  AddonStudies: "resource://normandy/lib/AddonStudies.sys.mjs",
  BaseAction: "resource://normandy/actions/BaseAction.sys.mjs",
  ClientEnvironment: "resource://normandy/lib/ClientEnvironment.sys.mjs",
  NormandyApi: "resource://normandy/lib/NormandyApi.sys.mjs",
  Sampling: "resource://gre/modules/components-utils/Sampling.sys.mjs",
  TelemetryEnvironment: "resource://gre/modules/TelemetryEnvironment.sys.mjs",
  TelemetryEvents: "resource://normandy/lib/TelemetryEvents.sys.mjs",
});

class AddonStudyEnrollError extends Error {
  /**
   * @param {string} studyName
   * @param {object} extra Extra details to include when reporting the error to telemetry.
   * @param {string} extra.reason The specific reason for the failure.
   */
  constructor(studyName, extra) {
    let message;
    let { reason } = extra;
    switch (reason) {
      case "conflicting-addon-id": {
        message = "an add-on with this ID is already installed";
        break;
      }
      case "download-failure": {
        message = "the add-on failed to download";
        break;
      }
      case "metadata-mismatch": {
        message = "the server metadata does not match the downloaded add-on";
        break;
      }
      case "install-failure": {
        message = "the add-on failed to install";
        break;
      }
      default: {
        throw new Error(`Unexpected AddonStudyEnrollError reason: ${reason}`);
      }
    }
    super(`Cannot install study add-on for ${studyName}: ${message}.`);
    this.studyName = studyName;
    this.extra = extra;
  }
}

class AddonStudyUpdateError extends Error {
  /**
   * @param {string} studyName
   * @param {object} extra Extra details to include when reporting the error to telemetry.
   * @param {string} extra.reason The specific reason for the failure.
   */
  constructor(studyName, extra) {
    let message;
    let { reason } = extra;
    switch (reason) {
      case "addon-id-mismatch": {
        message = "new add-on ID does not match old add-on ID";
        break;
      }
      case "addon-does-not-exist": {
        message = "an add-on with this ID does not exist";
        break;
      }
      case "no-downgrade": {
        message = "the add-on was an older version than is installed";
        break;
      }
      case "metadata-mismatch": {
        message = "the server metadata does not match the downloaded add-on";
        break;
      }
      case "download-failure": {
        message = "the add-on failed to download";
        break;
      }
      case "install-failure": {
        message = "the add-on failed to install";
        break;
      }
      default: {
        throw new Error(`Unexpected AddonStudyUpdateError reason: ${reason}`);
      }
    }
    super(`Cannot update study add-on for ${studyName}: ${message}.`);
    this.studyName = studyName;
    this.extra = extra;
  }
}

export class BranchedAddonStudyAction extends BaseStudyAction {
  get schema() {
    return lazy.ActionSchemas["branched-addon-study"];
  }

  constructor() {
    super();
    this.seenRecipeIds = new Set();
  }

  async _run(recipe) {
    throw new Error("_run should not be called anymore");
  }

  /**
   * This hook is executed once for every recipe currently enabled on the
   * server. It is responsible for:
   *
   *   - Enrolling studies the first time they have a FILTER_MATCH suitability.
   *   - Updating studies that have changed and still have a FILTER_MATCH suitability.
   *   - Marking studies as having been seen in this session.
   *   - Unenrolling studies when they have permanent errors.
   *   - Unenrolling studies when temporary errors persist for too long.
   *
   * If the action fails to perform any of these tasks, it should throw to
   * properly report its status.
   */
  async _processRecipe(recipe, suitability) {
    this.seenRecipeIds.add(recipe.id);
    const study = await lazy.AddonStudies.get(recipe.id);

    switch (suitability) {
      case lazy.BaseAction.suitability.FILTER_MATCH: {
        if (!study) {
          await this.enroll(recipe);
        } else if (study.active) {
          await this.update(recipe, study);
        }
        break;
      }

      case lazy.BaseAction.suitability.SIGNATURE_ERROR: {
        await this._considerTemporaryError({
          study,
          reason: "signature-error",
        });
        break;
      }

      case lazy.BaseAction.suitability.FILTER_ERROR: {
        await this._considerTemporaryError({
          study,
          reason: "filter-error",
        });
        break;
      }

      case lazy.BaseAction.suitability.CAPABILITIES_MISMATCH: {
        if (study?.active) {
          await this.unenroll(recipe.id, "capability-mismatch");
        }
        break;
      }

      case lazy.BaseAction.suitability.FILTER_MISMATCH: {
        if (study?.active) {
          await this.unenroll(recipe.id, "filter-mismatch");
        }
        break;
      }

      case lazy.BaseAction.suitability.ARGUMENTS_INVALID: {
        if (study?.active) {
          await this.unenroll(recipe.id, "arguments-invalid");
        }
        break;
      }

      default: {
        throw new Error(`Unknown recipe suitability "${suitability}".`);
      }
    }
  }

  /**
   * This hook is executed once after all recipes that apply to this client
   * have been processed. It is responsible for unenrolling the client from any
   * studies that no longer apply, based on this.seenRecipeIds.
   */
  async _finalize({ noRecipes } = {}) {
    const activeStudies = await lazy.AddonStudies.getAllActive({
      branched: lazy.AddonStudies.FILTER_BRANCHED_ONLY,
    });

    if (noRecipes) {
      if (this.seenRecipeIds.size) {
        throw new BranchedAddonStudyAction.BadNoRecipesArg();
      }
      for (const study of activeStudies) {
        await this._considerTemporaryError({ study, reason: "no-recipes" });
      }
    } else {
      for (const study of activeStudies) {
        if (!this.seenRecipeIds.has(study.recipeId)) {
          this.log.debug(
            `Stopping branched add-on study for recipe ${study.recipeId}`
          );
          try {
            await this.unenroll(study.recipeId, "recipe-not-seen");
          } catch (err) {
            console.error(err);
          }
        }
      }
    }
  }

  /**
   * Download and install the addon for a given recipe
   *
   * @param recipe Object describing the study to enroll in.
   * @param extensionDetails Object describing the addon to be installed.
   * @param onInstallStarted A function that returns a callback for the install listener.
   * @param onComplete A callback function that is run on completion of the download.
   * @param onFailedInstall A callback function that is run if the installation fails.
   * @param errorClass The class of error to be thrown when exceptions occur.
   * @param reportError A function that reports errors to Telemetry.
   * @param [errorExtra] Optional, an object that will be merged into the
   *                     `extra` field of the error generated, if any.
   */
  async downloadAndInstall({
    recipe,
    extensionDetails,
    branchSlug,
    onInstallStarted,
    onComplete,
    onFailedInstall,
    errorClass,
    reportError,
    errorExtra = {},
  }) {
    const { slug } = recipe.arguments;
    const { hash, hash_algorithm } = extensionDetails;

    const downloadDeferred = Promise.withResolvers();
    const installDeferred = Promise.withResolvers();

    const install = await lazy.AddonManager.getInstallForURL(
      extensionDetails.xpi,
      {
        hash: `${hash_algorithm}:${hash}`,
        telemetryInfo: { source: "internal" },
      }
    );

    const listener = {
      onDownloadFailed() {
        downloadDeferred.reject(
          new errorClass(slug, {
            reason: "download-failure",
            branch: branchSlug,
            detail: lazy.AddonManager.errorToString(install.error),
            ...errorExtra,
          })
        );
      },

      onDownloadEnded() {
        downloadDeferred.resolve();
        return false; // temporarily pause installation for Normandy bookkeeping
      },

      onInstallFailed() {
        installDeferred.reject(
          new errorClass(slug, {
            reason: "install-failure",
            branch: branchSlug,
            detail: lazy.AddonManager.errorToString(install.error),
          })
        );
      },

      onInstallEnded() {
        installDeferred.resolve();
      },
    };

    listener.onInstallStarted = onInstallStarted(installDeferred);

    install.addListener(listener);

    // Download the add-on
    try {
      install.install();
      await downloadDeferred.promise;
    } catch (err) {
      reportError(err);
      install.removeListener(listener);
      throw err;
    }

    await onComplete(install, listener);

    // Finish paused installation
    try {
      install.install();
      await installDeferred.promise;
    } catch (err) {
      reportError(err);
      install.removeListener(listener);
      await onFailedInstall();
      throw err;
    }

    install.removeListener(listener);

    return [install.addon.id, install.addon.version];
  }

  async chooseBranch({ slug, branches }) {
    const ratios = branches.map(branch => branch.ratio);
    const userId = lazy.ClientEnvironment.userId;

    // It's important that the input be:
    // - Unique per-user (no one is bucketed alike)
    // - Unique per-experiment (bucketing differs across multiple experiments)
    // - Differs from the input used for sampling the recipe (otherwise only
    //   branches that contain the same buckets as the recipe sampling will
    //   receive users)
    const input = `${userId}-${slug}-addon-branch`;

    const index = await lazy.Sampling.ratioSample(input, ratios);
    return branches[index];
  }

  /**
   * Enroll in the study represented by the given recipe.
   * @param recipe Object describing the study to enroll in.
   * @param extensionDetails Object describing the addon to be installed.
   */
  async enroll(recipe) {
    // This function first downloads the add-on to get its metadata. Then it
    // uses that metadata to record a study in `AddonStudies`. Then, it finishes
    // installing the add-on, and finally sends telemetry. If any of these steps
    // fails, the previous ones are undone, as needed.
    //
    // This ordering is important because the only intermediate states we can be
    // in are:
    //   1. The add-on is only downloaded, in which case AddonManager will clean it up.
    //   2. The study has been recorded, in which case we will unenroll on next
    //      start up. The start up code will assume that the add-on was uninstalled
    //      while the browser was shutdown.
    //   3. After installation is complete, but before telemetry, in which case we
    //      lose an enroll event. This is acceptable.
    //
    // This way a shutdown, crash or unexpected error can't leave Normandy in a
    // long term inconsistent state. The main thing avoided is having a study
    // add-on installed but no record of it, which would leave it permanently
    // installed.

    if (recipe.arguments.isEnrollmentPaused) {
      // Recipe does not need anything done
      return;
    }

    const { slug, userFacingName, userFacingDescription } = recipe.arguments;
    const branch = await this.chooseBranch({
      slug: recipe.arguments.slug,
      branches: recipe.arguments.branches,
    });
    this.log.debug(`Enrolling in branch ${branch.slug}`);

    if (branch.extensionApiId === null) {
      const study = {
        recipeId: recipe.id,
        slug,
        userFacingName,
        userFacingDescription,
        branch: branch.slug,
        addonId: null,
        addonVersion: null,
        addonUrl: null,
        extensionApiId: null,
        extensionHash: null,
        extensionHashAlgorithm: null,
        active: true,
        studyStartDate: new Date(),
        studyEndDate: null,
        temporaryErrorDeadline: null,
      };

      try {
        await lazy.AddonStudies.add(study);
      } catch (err) {
        this.reportEnrollError(err);
        throw err;
      }

      // All done, report success to Telemetry
      lazy.TelemetryEvents.sendEvent("enroll", "addon_study", slug, {
        addonId: lazy.AddonStudies.NO_ADDON_MARKER,
        addonVersion: lazy.AddonStudies.NO_ADDON_MARKER,
        branch: branch.slug,
      });
    } else {
      const extensionDetails = await lazy.NormandyApi.fetchExtensionDetails(
        branch.extensionApiId
      );

      const onInstallStarted = installDeferred => cbInstall => {
        const versionMatches =
          cbInstall.addon.version === extensionDetails.version;
        const idMatches = cbInstall.addon.id === extensionDetails.extension_id;

        if (cbInstall.existingAddon) {
          installDeferred.reject(
            new AddonStudyEnrollError(slug, {
              reason: "conflicting-addon-id",
              branch: branch.slug,
            })
          );
          return false; // cancel the installation, no upgrades allowed
        } else if (!versionMatches || !idMatches) {
          installDeferred.reject(
            new AddonStudyEnrollError(slug, {
              branch: branch.slug,
              reason: "metadata-mismatch",
            })
          );
          return false; // cancel the installation, server metadata does not match downloaded add-on
        }
        return true;
      };

      let study;
      const onComplete = async (install, listener) => {
        study = {
          recipeId: recipe.id,
          slug,
          userFacingName,
          userFacingDescription,
          branch: branch.slug,
          addonId: install.addon.id,
          addonVersion: install.addon.version,
          addonUrl: extensionDetails.xpi,
          extensionApiId: branch.extensionApiId,
          extensionHash: extensionDetails.hash,
          extensionHashAlgorithm: extensionDetails.hash_algorithm,
          active: true,
          studyStartDate: new Date(),
          studyEndDate: null,
          temporaryErrorDeadline: null,
        };

        try {
          await lazy.AddonStudies.add(study);
        } catch (err) {
          this.reportEnrollError(err);
          install.removeListener(listener);
          install.cancel();
          throw err;
        }
      };

      const onFailedInstall = async () => {
        await lazy.AddonStudies.delete(recipe.id);
      };

      const [installedId, installedVersion] = await this.downloadAndInstall({
        recipe,
        branchSlug: branch.slug,
        extensionDetails,
        onInstallStarted,
        onComplete,
        onFailedInstall,
        errorClass: AddonStudyEnrollError,
        reportError: this.reportEnrollError,
      });

      // All done, report success to Telemetry
      lazy.TelemetryEvents.sendEvent("enroll", "addon_study", slug, {
        addonId: installedId,
        addonVersion: installedVersion,
        branch: branch.slug,
      });
    }

    lazy.TelemetryEnvironment.setExperimentActive(slug, branch.slug, {
      type: "normandy-addonstudy",
    });
  }

  /**
   * Update the study represented by the given recipe.
   * @param recipe Object describing the study to be updated.
   * @param extensionDetails Object describing the addon to be installed.
   */
  async update(recipe, study) {
    const { slug } = recipe.arguments;

    // Stay in the same branch, don't re-sample every time.
    const branch = recipe.arguments.branches.find(
      branch => branch.slug === study.branch
    );

    if (!branch) {
      // Our branch has been removed. Unenroll.
      await this.unenroll(recipe.id, "branch-removed");
      return;
    }

    // Since we saw a non-error suitability, clear the temporary error deadline.
    study.temporaryErrorDeadline = null;
    await lazy.AddonStudies.update(study);

    const extensionDetails = await lazy.NormandyApi.fetchExtensionDetails(
      branch.extensionApiId
    );

    let error;

    if (study.addonId && study.addonId !== extensionDetails.extension_id) {
      error = new AddonStudyUpdateError(slug, {
        branch: branch.slug,
        reason: "addon-id-mismatch",
      });
    }

    const versionCompare = Services.vc.compare(
      study.addonVersion,
      extensionDetails.version
    );
    if (versionCompare > 0) {
      error = new AddonStudyUpdateError(slug, {
        branch: branch.slug,
        reason: "no-downgrade",
      });
    } else if (versionCompare === 0) {
      return; // Unchanged, do nothing
    }

    if (error) {
      this.reportUpdateError(error);
      throw error;
    }

    const onInstallStarted = installDeferred => cbInstall => {
      const versionMatches =
        cbInstall.addon.version === extensionDetails.version;
      const idMatches = cbInstall.addon.id === extensionDetails.extension_id;

      if (!cbInstall.existingAddon) {
        installDeferred.reject(
          new AddonStudyUpdateError(slug, {
            branch: branch.slug,
            reason: "addon-does-not-exist",
          })
        );
        return false; // cancel the installation, must upgrade an existing add-on
      } else if (!versionMatches || !idMatches) {
        installDeferred.reject(
          new AddonStudyUpdateError(slug, {
            branch: branch.slug,
            reason: "metadata-mismatch",
          })
        );
        return false; // cancel the installation, server metadata do not match downloaded add-on
      }

      return true;
    };

    const onComplete = async (install, listener) => {
      try {
        await lazy.AddonStudies.update({
          ...study,
          addonVersion: install.addon.version,
          addonUrl: extensionDetails.xpi,
          extensionHash: extensionDetails.hash,
          extensionHashAlgorithm: extensionDetails.hash_algorithm,
          extensionApiId: branch.extensionApiId,
        });
      } catch (err) {
        this.reportUpdateError(err);
        install.removeListener(listener);
        install.cancel();
        throw err;
      }
    };

    const onFailedInstall = () => {
      lazy.AddonStudies.update(study);
    };

    const [installedId, installedVersion] = await this.downloadAndInstall({
      recipe,
      extensionDetails,
      branchSlug: branch.slug,
      onInstallStarted,
      onComplete,
      onFailedInstall,
      errorClass: AddonStudyUpdateError,
      reportError: this.reportUpdateError,
      errorExtra: {},
    });

    // All done, report success to Telemetry
    lazy.TelemetryEvents.sendEvent("update", "addon_study", slug, {
      addonId: installedId,
      addonVersion: installedVersion,
      branch: branch.slug,
    });
  }

  reportEnrollError(error) {
    if (error instanceof AddonStudyEnrollError) {
      // One of our known errors. Report it nicely to telemetry
      lazy.TelemetryEvents.sendEvent(
        "enrollFailed",
        "addon_study",
        error.studyName,
        error.extra
      );
    } else {
      /*
       * Some unknown error. Add some helpful details, and report it to
       * telemetry. The actual stack trace and error message could possibly
       * contain PII, so we don't include them here. Instead include some
       * information that should still be helpful, and is less likely to be
       * unsafe.
       */
      const safeErrorMessage = `${error.fileName}:${error.lineNumber}:${error.columnNumber} ${error.name}`;
      lazy.TelemetryEvents.sendEvent(
        "enrollFailed",
        "addon_study",
        error.studyName,
        {
          reason: safeErrorMessage.slice(0, 80), // max length is 80 chars
        }
      );
    }
  }

  reportUpdateError(error) {
    if (error instanceof AddonStudyUpdateError) {
      // One of our known errors. Report it nicely to telemetry
      lazy.TelemetryEvents.sendEvent(
        "updateFailed",
        "addon_study",
        error.studyName,
        error.extra
      );
    } else {
      /*
       * Some unknown error. Add some helpful details, and report it to
       * telemetry. The actual stack trace and error message could possibly
       * contain PII, so we don't include them here. Instead include some
       * information that should still be helpful, and is less likely to be
       * unsafe.
       */
      const safeErrorMessage = `${error.fileName}:${error.lineNumber}:${error.columnNumber} ${error.name}`;
      lazy.TelemetryEvents.sendEvent(
        "updateFailed",
        "addon_study",
        error.studyName,
        {
          reason: safeErrorMessage.slice(0, 80), // max length is 80 chars
        }
      );
    }
  }

  /**
   * Unenrolls the client from the study with a given recipe ID.
   * @param recipeId The recipe ID of an enrolled study
   * @param reason The reason for this unenrollment, to be used in Telemetry
   * @throws If the specified study does not exist, or if it is already inactive.
   */
  async unenroll(recipeId, reason = "unknown") {
    const study = await lazy.AddonStudies.get(recipeId);
    if (!study) {
      throw new Error(`No study found for recipe ${recipeId}.`);
    }
    if (!study.active) {
      throw new Error(
        `Cannot stop study for recipe ${recipeId}; it is already inactive.`
      );
    }

    await lazy.AddonStudies.markAsEnded(study, reason);

    // Study branches may indicate that no add-on should be installed, as a
    // form of control branch. In that case, `study.addonId` will be null (as
    // will the other add-on related fields). Only try to uninstall the add-on
    // if we expect one should be installed.
    if (study.addonId) {
      const addon = await lazy.AddonManager.getAddonByID(study.addonId);
      if (addon) {
        await addon.uninstall();
      } else {
        this.log.warn(
          `Could not uninstall addon ${study.addonId} for recipe ${study.recipeId}: it is not installed.`
        );
      }
    }
  }

  /**
   * Given that a temporary error has occured for a study, check if it
   * should be temporarily ignored, or if the deadline has passed. If the
   * deadline is passed, the study will be ended. If this is the first
   * temporary error, a deadline will be generated. Otherwise, nothing will
   * happen.
   *
   * If a temporary deadline exists but cannot be parsed, a new one will be
   * made.
   *
   * The deadline is 7 days from the first time that recipe failed, as
   * reckoned by the client's clock.
   *
   * @param {Object} args
   * @param {Study} args.study The enrolled study to potentially unenroll.
   * @param {String} args.reason If the study should end, the reason it is ending.
   */
  async _considerTemporaryError({ study, reason }) {
    if (!study?.active) {
      return;
    }

    let now = Date.now(); // milliseconds-since-epoch
    let day = 24 * 60 * 60 * 1000;
    let newDeadline = new Date(now + 7 * day);

    if (study.temporaryErrorDeadline) {
      // if deadline is an invalid date, set it to one week from now.
      if (isNaN(study.temporaryErrorDeadline)) {
        study.temporaryErrorDeadline = newDeadline;
        await lazy.AddonStudies.update(study);
        return;
      }

      if (now > study.temporaryErrorDeadline) {
        await this.unenroll(study.recipeId, reason);
      }
    } else {
      // there is no deadline, so set one
      study.temporaryErrorDeadline = newDeadline;
      await lazy.AddonStudies.update(study);
    }
  }
}

BranchedAddonStudyAction.BadNoRecipesArg = class extends Error {
  message = "noRecipes is true, but some recipes observed";
};