;;; ghpr-api.el --- Interactions for the GitHub API -*- lexical-binding: t -*-

;; This file is not part of GNU Emacs

;; This program is free software: you can redistribute it and/or modify
;; it under the terms of the GNU General Public License as published by
;; the Free Software Foundation, either version 3 of the License, or
;; (at your option) any later version.

;; This program is distributed in the hope that it will be useful,
;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
;; GNU General Public License for more details.

;; You should have received a copy of the GNU General Public License
;; along with this program.  If not, see <https://www.gnu.org/licenses/>.


;;; Commentary:

;; Provides procedures for interacting with the GitHub API, including
;; authentication.

;;; Code:

(require 'auth-source)
(require 'request)
(require 'json)

(defun ghpr--get-token ()
  "Retrieve GitHub authentication token from auth-sources.
Returns the token string if found, nil otherwise."
  (auth-source-pick-first-password :host "api.github.com"))

(defun ghpr--parse-api-pr (pr)
  "Parse a single pull request object, keeping only essential fields."
  (let* ((get (lambda (field) (alist-get field pr)))
         (base (get 'base))
         (user (get 'user)))
    `((url . ,(get 'url))
      (id . ,(get 'id))
      (diff_url . ,(get 'diff_url))
      (patch_url . ,(get 'patch_url))
      (number . ,(get 'number))
      (state . ,(get 'state))
      (locked . ,(get 'locked))
      (title . ,(get 'title))
      (body . ,(get 'body))
      (username . ,(alist-get 'login user))
      (base_sha . ,(alist-get 'sha base))
      (merge_commit_sha . ,(get 'merge_commit_sha)))))

(defun ghpr--parse-api-pr-list (pr-list)
  "Parse a list of pull request objects, keeping only essential fields."
  (mapcar #'ghpr--parse-api-pr pr-list))

(defun ghpr--list-open-prs (repo-name)
  "List open pull requests for REPO-NAME in owner/repo format.
Returns a list of pull request objects on success, nil on failure."
  (let ((token (ghpr--get-token))
        (url (format "https://api.github.com/repos/%s/pulls?state=open" repo-name))
        (result nil))
    (when token
      (request url
        :type "GET"
        :headers `(("Accept" . "application/vnd.github+json")
                   ("Authorization" . ,(format "Bearer %s" token))
                   ("X-GitHub-Api-Version" . "2022-11-28"))
        :parser 'json-read
        :sync t
        :success (cl-function
                  (lambda (&key data &allow-other-keys)
                    (setq result (ghpr--parse-api-pr-list data))))
        :error (cl-function
                (lambda (&key error-thrown &allow-other-keys)
                  (message "Error fetching pull requests: %s" error-thrown)))))
    result))

(provide 'ghpr-api)

;;; ghpr-api.el ends here