;;; my-net.el -- Network related extensions for emacs core -*- lexical-binding: t -*-

;; Copyright (C) 2023 Free Software Foundation.

;; Author: Yuchen Pei <id@ypei.org>
;; Package-Requires: ((emacs "28.2"))

;; This file is part of dotfiles.

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

;; dotfiles 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 Affero General
;; Public License for more details.

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

;;; Commentary:

;; Network related extensions for emacs core.

;;; Code:


;;; net utilities
(defvar my-download-dir "~/Downloads")

(defun my-make-file-name-from-url (url)
  (file-name-nondirectory
   (directory-file-name
    (car (url-path-and-query (url-generic-parse-url
                              (url-unhex-string url)))))))

;; stolen from `eww-make-unique-file-name'
(defun my-make-unique-file-name (file directory)
  "Uniquefy FILE under DIRECTORY.

Like `expand-file-name', but make sure the file name has not been taken."
  (cond
   ((zerop (length file))
    (setq file "!"))
   ((string-match "\\`[.]" file)
    (setq file (concat "!" file))))
  (let ((count 1)
        (stem file)
        (suffix ""))
    (when (string-match "\\`\\(.*\\)\\([.][^.]+\\)" file)
      (setq stem (match-string 1 file)
            suffix (match-string 2 file)))
    (while (file-exists-p (expand-file-name file directory))
      (setq file (format "%s(%d)%s" stem count suffix))
      (setq count (1+ count)))
    (expand-file-name file directory)))

(defun my-fetch-url (url &optional no-overwrite)
  "Fetch URL to a buffer, save it to a file, and switch to the buffer.

The file is saved under `my-download-dir'.
If NO-OVERWRITE is non-nil, do not overwrite any existing file."
  (interactive "sURL: ")
  (let ((file-name
         (if no-overwrite
             (my-make-unique-file-name
              (my-make-file-name-from-url url)
              my-download-dir)
           (expand-file-name
            (my-make-file-name-from-url url)
            my-download-dir))))
    (url-retrieve url 'my-fetch-url-save-and-switch (list file-name))))

(defun my-fetch-url-save-and-switch (status file-name)
  "A `url-retrieve' callback that saves the payload and switch to it.

It checks the STATUS, and if it is ok, saves the payload to FILE-NAME."
  (when (plist-get status :error)
    (error "My fetch failed: %s" (plist-get status :error)))
  (my-delete-http-header)
  (let ((to-insert (buffer-string))
        (buffer (find-file-noselect file-name))
        (coding-system-for-write 'utf-8))
    (kill-buffer)
    (with-current-buffer buffer
      (let ((inhibit-read-only t))
        (erase-buffer)
        (insert to-insert))
      (goto-char (point-min))
      (save-buffer)
      (revert-buffer t t))
    (switch-to-buffer buffer))
  )

(defun my-kill-http-header ()
  (my-skip-http-header)
  (let ((killed (buffer-substring-no-properties (point-min) (point))))
    (delete-region (point-min) (point))
    killed))

(defun my-parse-http-header (text)
  (let ((status) (fields))
    (with-temp-buffer
      (insert text)
      (goto-char (point-min))
      (re-search-forward "^HTTP.*\\([0-9]\\{3\\}\\).*$")
      (setq status (match-string 1))
      (while (re-search-forward "^\\(.*?\\): \\(.*\\)$" nil t)
        (push (cons (intern (match-string 1)) (match-string 2)) fields)))
    (list (cons 'status status) (cons 'fields fields))))

(defvar my-client-buffer-name "*my-api*")

(defun my-url-fetch-json (url &optional decompression with-header)
  (my-url-fetch-internal
   url
   (lambda ()
     (json-read-from-string (decode-coding-string (buffer-string) 'utf-8)))
   decompression
   with-header))

(defun my-url-fetch-dom (url &optional decompression with-header)
  (my-url-fetch-internal
   url
   (lambda () (libxml-parse-html-region (point) (point-max)))
   decompression
   with-header))

(defun my-url-fetch-internal (url buffer-processor decompression with-header)
  (with-current-buffer (get-buffer-create my-client-buffer-name)
    (goto-char (point-max))
    (insert "[" (current-time-string) "] Request: " url "\n"))
  (with-current-buffer (url-retrieve-synchronously url t)
    (let ((header (my-kill-http-header)) (status) (fields))
      (goto-char (point-min))
      (setq header (my-parse-http-header header)
            status (alist-get 'status header)
            fields (alist-get 'fields header))
      (with-current-buffer my-client-buffer-name
        (insert "[" (current-time-string) "] Response: " status "\n"))
      (when decompression
        (call-process-region (point) (point-max) "gunzip" t t t)
        (goto-char (point-min)))
      (call-interactively 'delete-trailing-whitespace)
      (if (string= status "200")
          (unless (= (point) (point-max))
            (if with-header
                (list
                 (cons 'header fields)
                 (cons 'json (funcall buffer-processor)))
              (funcall buffer-processor)))
        (error "HTTP error: %s" (buffer-substring (point) (point-max)))))))

(provide 'my-net)
;;; my-net.el ends here