// @flow

import browserslist from "browserslist";
import semver from "semver";
import { semverify } from "./utils";
import type { Targets } from "./types";

const browserNameMap = {
  android: "android",
  chrome: "chrome",
  edge: "edge",
  firefox: "firefox",
  ie: "ie",
  ios_saf: "ios",
  safari: "safari",
};

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

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

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];
      const parsedBrowserVersion = semverify(splitVersion);

      all[normalizedBrowserName] = semverMin(
        all[normalizedBrowserName],
        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 targetParserMap = {
  __default: (target, value) => [target, semverify(value)],

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

    return [target, parsed];
  },
};

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

  // Parse browsers target via browserslist
  if (isBrowsersQueryValid(targets.browsers)) {
    targetOpts = getLowestVersions(browserslist(targets.browsers));
  }

  // Parse remaining targets
  type ParsedResult = {
    targets: Targets,
    decimalWarnings: Array<Object>,
  };
  const parsed = Object.keys(targets).reduce(
    (results: ParsedResult, target: string): ParsedResult => {
      if (target !== "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] = semverMin(
            results.targets[parsedTarget],
            parsedValue,
          );
        }
      }

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

  outputDecimalWarning(parsed.decimalWarnings);

  return parsed.targets;
};

export default getTargets;