'use strict';
const valueParser = require('postcss-value-parser');

const getValue = (node) => parseFloat(node.value);

/* Works because toString() normalizes the formatting,
   so comparing the string forms behaves the same as number equality*/
const conversions = new Map([
  [[0.25, 0.1, 0.25, 1].toString(), 'ease'],
  [[0, 0, 1, 1].toString(), 'linear'],
  [[0.42, 0, 1, 1].toString(), 'ease-in'],
  [[0, 0, 0.58, 1].toString(), 'ease-out'],
  [[0.42, 0, 0.58, 1].toString(), 'ease-in-out'],
]);
function reduce(node) {
  if (node.type !== 'function') {
    return false;
  }

  if (!node.value) {
    return;
  }

  const lowerCasedValue = node.value.toLowerCase();

  if (lowerCasedValue === 'steps') {
    // Don't bother checking the step-end case as it has the same length
    // as steps(1)
    if (
      node.nodes[0].type === 'word' &&
      getValue(node.nodes[0]) === 1 &&
      node.nodes[2] &&
      node.nodes[2].type === 'word' &&
      (node.nodes[2].value.toLowerCase() === 'start' ||
        node.nodes[2].value.toLowerCase() === 'jump-start')
    ) {
      node.type = 'word';
      node.value = 'step-start';

      delete node.nodes;

      return;
    }

    if (
      node.nodes[0].type === 'word' &&
      getValue(node.nodes[0]) === 1 &&
      node.nodes[2] &&
      node.nodes[2].type === 'word' &&
      (node.nodes[2].value.toLowerCase() === 'end' ||
        node.nodes[2].value.toLowerCase() === 'jump-end')
    ) {
      node.type = 'word';
      node.value = 'step-end';

      delete node.nodes;

      return;
    }

    // The end case is actually the browser default, so it isn't required.
    if (
      node.nodes[2] &&
      node.nodes[2].type === 'word' &&
      (node.nodes[2].value.toLowerCase() === 'end' ||
        node.nodes[2].value.toLowerCase() === 'jump-end')
    ) {
      node.nodes = [node.nodes[0]];

      return;
    }

    return false;
  }

  if (lowerCasedValue === 'cubic-bezier') {
    const values = node.nodes
      .filter((list, index) => {
        return index % 2 === 0;
      })
      .map(getValue);

    if (values.length !== 4) {
      return;
    }

    const match = conversions.get(values.toString());

    if (match) {
      node.type = 'word';
      node.value = match;

      delete node.nodes;

      return;
    }
  }
}

function transform(value) {
  return valueParser(value).walk(reduce).toString();
}

function pluginCreator() {
  return {
    postcssPlugin: 'postcss-normalize-timing-functions',

    OnceExit(css) {
      const cache = new Map();

      css.walkDecls(
        /^(-\w+-)?(animation|transition)(-timing-function)?$/i,
        (decl) => {
          const value = decl.value;

          if (cache.has(value)) {
            decl.value = cache.get(value);

            return;
          }

          const result = transform(value);

          decl.value = result;
          cache.set(value, result);
        }
      );
    },
  };
}

pluginCreator.postcss = true;
module.exports = pluginCreator;