import * as utils from "../../utils";
import type {
  RuleFix,
  RuleListener
} from "@typescript-eslint/utils/dist/ts-eslint";
import type { TSESTree } from "@typescript-eslint/utils";
import { s } from "typescript-misc";

export enum MessageId {
  addEmptyLine = "addEmptyLine",
  removeEmptyLine = "removeEmptyLine"
}

export const commentSpacing = utils.createRule({
  name: "comment-spacing",
  fixable: utils.Fixable.whitespace,
  messages: {
    [MessageId.addEmptyLine]: "Add empty line after comment",
    [MessageId.removeEmptyLine]: "Remove empty line after comment"
  },
  docs: {
    description: "Requires consistent empty lines around comments.",
    failExamples: `
      // Comment
      function f() {}

      /** Comment */
      function g() {}

      /*
      Comment
      */

      function h() {}
    `,
    passExamples: `
      // Comment

      function f() {}

      /** Comment */

      function g() {}

      /*
      Comment
      */
      function h() {}
    `
  },
  create: (context): RuleListener => {
    return {
      ":statement, TSDeclareFunction, TSExportAssignment": (
        node: TSESTree.Node
      ) => {
        for (const range of context.getCommentRanges(node)) {
          const multiline = isMultiline(context.getText(range));

          const nextMultiline = isMultiline(context.getText(range[1]));

          const spread = multiline && !nextMultiline;

          const got = s.leadingSpaces(context.getText(range[1]));

          const expected =
            context.eol.repeat(spread ? 2 : 1) + s.trimLeadingEmptyLines(got);

          if (got === expected) {
            // Valid
          } else
            context.report({
              fix: (): RuleFix => {
                return {
                  range: [range[1], range[1] + got.length],
                  text: expected
                };
              },
              loc: context.getLoc(range),
              messageId: spread
                ? MessageId.addEmptyLine
                : MessageId.removeEmptyLine
            });
        }
      }
    };
  }
});

/**
 * Checks if string starts with multiline comment.
 * @param str - String.
 * @returns _True_ if string starts with multiline comment, _false_ otherwise.
 */
function isMultiline(str: string): boolean {
  str = str.trimStart();

  return str.startsWith("/*") && !str.startsWith("/**");
}