// @flow

import browserslist from "browserslist";
import invariant from "invariant";
import semver from "semver";
import {
  semverify,
  isUnreleasedVersion,
  getLowestUnreleased,
  findSuggestion,
} from "./utils";
import browserModulesData from "../data/built-in-modules.json";
import { TargetNames } from "./options";
import type { Targets } from "./types";

const browserslistDefaults = browserslist.defaults;

const validBrowserslistTargets = [
  ...Object.keys(browserslist.data),
  ...Object.keys(browserslist.aliases),
];

const objectToBrowserslist = (object: Targets): Array<string> => {
  return Object.keys(object).reduce((list, targetName) => {
    if (validBrowserslistTargets.indexOf(targetName) >= 0) {
      const targetVersion = object[targetName];
      return list.concat(`${targetName} ${targetVersion}`);
    }
    return list;
  }, []);
};

const validateTargetNames = (targets: Targets): void => {
  const validTargets = Object.keys(TargetNames);
  for (const target in targets) {
    if (!TargetNames[target]) {
      throw new Error(
        `Invalid Option: '${target}' is not a valid target
        Maybe you meant to use '${findSuggestion(validTargets, target)}'?`,
      );
    }
  }
};

const browserNameMap = {
  and_chr: "chrome",
  and_ff: "firefox",
  android: "android",
  chrome: "chrome",
  edge: "edge",
  firefox: "firefox",
  ie: "ie",
  ie_mob: "ie",
  ios_saf: "ios",
  node: "node",
  op_mob: "opera",
  opera: "opera",
  safari: "safari",
  samsung: "samsung",
};

export const isBrowsersQueryValid = (
  browsers: string | Array<string> | Targets,
): boolean => typeof browsers === "string" || Array.isArray(browsers);

const validateBrowsers = browsers => {
  invariant(
    typeof browsers === "undefined" || isBrowsersQueryValid(browsers),
    `Invalid Option: '${browsers}' is not a valid browserslist query`,
  );

  return browsers;
};

export const semverMin = (first: ?string, second: string): string => {
  return first && semver.lt(first, second) ? first : second;
};

const mergeBrowsers = (fromQuery: Targets, fromTarget: Targets) => {
  return Object.keys(fromTarget).reduce((queryObj, targKey) => {
    if (targKey !== TargetNames.browsers) {
      queryObj[targKey] = fromTarget[targKey];
    }
    return queryObj;
  }, fromQuery);
};

const getLowestVersions = (browsers: Array<string>): Targets => {
  return browsers.reduce((all: Object, browser: string): Object => {
    const [browserName, browserVersion] = browser.split(" ");
    const normalizedBrowserName = browserNameMap[browserName];

    if (!normalizedBrowserName) {
      return all;
    }

    try {
      // Browser version can return as "10.0-10.2"
      const splitVersion = browserVersion.split("-")[0].toLowerCase();
      const isSplitUnreleased = isUnreleasedVersion(splitVersion, browserName);

      if (!all[normalizedBrowserName]) {
        all[normalizedBrowserName] = isSplitUnreleased
          ? splitVersion
          : semverify(splitVersion);
        return all;
      }

      const version = all[normalizedBrowserName];
      const isUnreleased = isUnreleasedVersion(version, browserName);

      if (isUnreleased && isSplitUnreleased) {
        all[normalizedBrowserName] = getLowestUnreleased(
          version,
          splitVersion,
          browserName,
        );
      } else if (isUnreleased) {
        all[normalizedBrowserName] = semverify(splitVersion);
      } else if (!isUnreleased && !isSplitUnreleased) {
        const parsedBrowserVersion = semverify(splitVersion);

        all[normalizedBrowserName] = semverMin(version, parsedBrowserVersion);
      }
    } catch (e) {}

    return all;
  }, {});
};

const outputDecimalWarning = (decimalTargets: Array<Object>): void => {
  if (!decimalTargets || !decimalTargets.length) {
    return;
  }

  console.log("Warning, the following targets are using a decimal version:");
  console.log("");
  decimalTargets.forEach(({ target, value }) =>
    console.log(`  ${target}: ${value}`),
  );
  console.log("");
  console.log(
    "We recommend using a string for minor/patch versions to avoid numbers like 6.10",
  );
  console.log("getting parsed as 6.1, which can lead to unexpected behavior.");
  console.log("");
};

const semverifyTarget = (target, value) => {
  try {
    return semverify(value);
  } catch (error) {
    throw new Error(
      `Invalid Option: '${value}' is not a valid value for 'targets.${target}'.`,
    );
  }
};

const targetParserMap = {
  __default: (target, value) => {
    const version = isUnreleasedVersion(value, target)
      ? value.toLowerCase()
      : semverifyTarget(target, value);
    return [target, version];
  },

  // Parse `node: true` and `node: "current"` to version
  node: (target, value) => {
    const parsed =
      value === true || value === "current"
        ? process.versions.node
        : semverifyTarget(target, value);
    return [target, parsed];
  },
};

type ParsedResult = {
  targets: Targets,
  decimalWarnings: Array<Object>,
};

const getTargets = (targets: Object = {}, options: Object = {}): Targets => {
  const targetOpts: Targets = {};

  validateTargetNames(targets);

  // `esmodules` as a target indicates the specific set of browsers supporting ES Modules.
  // These values OVERRIDE the `browsers` field.
  if (targets.esmodules) {
    const supportsESModules = browserModulesData["es6.module"];
    targets.browsers = Object.keys(supportsESModules)
      .map(browser => `${browser} ${supportsESModules[browser]}`)
      .join(", ");
  }

  // Parse browsers target via browserslist
  const browsersquery = validateBrowsers(targets.browsers);

  const hasTargets = Object.keys(targets).length > 0;
  const shouldParseBrowsers = !!targets.browsers;
  const shouldSearchForConfig =
    !options.ignoreBrowserslistConfig && !hasTargets;

  if (shouldParseBrowsers || shouldSearchForConfig) {
    // If no targets are passed, we need to overwrite browserslist's defaults
    // so that we enable all transforms (acting like the now deprecated
    // preset-latest).
    //
    // Note, if browserslist resolves the config (ex. package.json), then usage
    // of `defaults` in queries will be different since we don't want to break
    // the behavior of "no targets is the same as preset-latest".
    if (!hasTargets) {
      browserslist.defaults = objectToBrowserslist(targets);
    }

    const browsers = browserslist(browsersquery, {
      path: options.configPath,
      mobileToDesktop: true,
    });

    const queryBrowsers = getLowestVersions(browsers);
    targets = mergeBrowsers(queryBrowsers, targets);

    // Reset browserslist defaults
    browserslist.defaults = browserslistDefaults;
  }

  // Parse remaining targets
  const parsed = Object.keys(targets)
    .filter(value => value !== TargetNames.esmodules)
    .sort()
    .reduce(
      (results: ParsedResult, target: string): ParsedResult => {
        if (target !== TargetNames.browsers) {
          const value = targets[target];

          // Warn when specifying minor/patch as a decimal
          if (typeof value === "number" && value % 1 !== 0) {
            results.decimalWarnings.push({ target, value });
          }

          // Check if we have a target parser?
          const parser = targetParserMap[target] || targetParserMap.__default;
          const [parsedTarget, parsedValue] = parser(target, value);

          if (parsedValue) {
            // Merge (lowest wins)
            results.targets[parsedTarget] = parsedValue;
          }
        }

        return results;
      },
      {
        targets: targetOpts,
        decimalWarnings: [],
      },
    );

  outputDecimalWarning(parsed.decimalWarnings);

  return parsed.targets;
};

export default getTargets;