(require 'cl-lib)

(defvar structlog-fields nil
  "Currently selected structlog fields")
(defvar structlog-logs nil
  "Current structlog log lines, formatted as plists")

(defun structlog--make-list-entries ()
  "Makes the tabulated-list-mode entries list for structlog"
  (cl-map 'list
          (lambda (log-plist)
            (list log-plist
                  (cl-map 'vector
                          (lambda (field)
                            (plist-get log-plist field))
                          structlog-fields)))
          structlog-logs))

(define-derived-mode structlog-mode tabulated-list-mode "structlog"
  "Major mode to query structured log lines"
  (setq tabulated-list-format
        (cl-map 'vector
                (lambda (field)
                  (list (symbol-name field) 20 t))
                structlog-fields)
        tabulated-list-entries #'structlog--make-list-entries)
  (tabulated-list-init-header))

;;;###autoload
(defun structlog ()
  (interactive)
  (when (get-buffer "*structlog*")
    (kill-buffer "*structlog*"))
  (with-current-buffer (get-buffer-create "*structlog*")
    ;; TODO do something real here
    (setq structlog-fields '(time event)
          structlog-logs '((time "2020-06-02T16:55:00" event "Got a baz")
                           (time "2020-06-02T17:00:00" event "Got a bar")
                           (time "2020-06-02T17:04:00" event "Got a foo")))
    (structlog-mode)
    (tabulated-list-print))
  (switch-to-buffer "*structlog*"))