import * as t from '@babel/types';
import generate from '@babel/generator';

import { stripIndent } from 'common-tags';

type Printable = t.Node | string;

export default class Printer {
  private printQueue: Printable[] = []

  public print(): string {
    return this.printQueue
      .reduce(
        (document: string, printable) => {
          if (typeof printable === 'string') {
            return document + printable;
          } else {
            const documentPart = generate(printable).code;
            return document + this.fixCommas(documentPart);
          }
        },
        ''
      ) as string;
  }

  public enqueue(printable: Printable) {
    this.printQueue = [
      ...this.printQueue,
      '\n',
      '\n',
      printable
    ];
  }

  public printAndClear() {
    const output = this.print();
    this.printQueue = [];
    return output;
  }

  /**
   * When using trailing commas on ObjectTypeProperties within
   * ObjectTypeAnnotations, we get weird behavior:
   * ```
   * {
   *   homePlanet: ?string // description
   *   ,
   *   friends: any  // description
   * }
   * ```
   * when we want
   * ```
   * {
   *   homePlanet: ?string, // description
   *   friends: any         // description
   * }
   * ```
   */
  private fixCommas(documentPart: string) {
    const lines = documentPart.split('\n');
    let currentLine = 0;
    let nextLine;
    const newDocumentParts = [];
    // Keep track of what column comments should start on
    // to keep things aligned
    let maxCommentColumn = 0;

    while (currentLine !== lines.length) {
      nextLine = currentLine + 1;
      const strippedNextLine = stripIndent`${lines[nextLine]}`;
      if (strippedNextLine.length === 1 && strippedNextLine[0] === ',') {
        const currentLineContents = lines[currentLine];
        const commentColumn = currentLineContents.indexOf('//');
        if (maxCommentColumn < commentColumn) {
          maxCommentColumn = commentColumn;
        }

        const [contents, comment] = currentLineContents.split('//');
        newDocumentParts.push({
          main: contents.replace(/\s+$/g, '') + ',',
          comment: comment ? comment.trim() : null
        });
        currentLine++;
      } else {
        newDocumentParts.push({
          main: lines[currentLine],
          comment: null
        });
      }

      currentLine++;
    }

    return newDocumentParts.reduce((memo: string[], part) => {
      const {
        main,
        comment
      } = part;

      let line;
      if (comment !== null) {
        const spacesBetween = maxCommentColumn - main.length;
        line = `${main}${' '.repeat(spacesBetween)} // ${comment}`
      } else {
        line = main;
      }

      return [
        ...memo,
        line
      ];
    }, []).join('\n');
  }
}