;;; dklrt.el --- Ledger Recurring Transactions.

;; Copyright: (c) David Keegan 2011-2013.
;; Licence: FSF GPLv3.
;; Author: David Keegan <dksw@eircom.net>
;; Version: 1.0
;; Package-Requires: ((dkmisc "0.5") (ledger-mode "20130908.1357") (emacs "24.1"))
;; Keywords: ledger ledger-cli recurring periodic automatic
;; URL: https://github.com/davidkeegan/dklrt

;;; Commentary:

;; An add-on to ledger-mode which appends recurring transactions to
;; the current ledger file, usually on entry to ledger-mode. Recurring
;; transactions are configured in a separate file which conforms to
;; ledger file format and resides in the same directory as the ledger
;; file.

;;; Code:

(require 'dkmisc)
(require 'ledger-mode)

;;;###autoload
(defgroup dklrt nil
 "Package dklrt (Ledger Recurring Transactions)."
 :tag "dklrt"
 :group 'dk)

(defcustom dklrt-SortAfterAppend nil
 "Controls positioning of appended recurring transactions.
If non-nil, sort the ledger buffer after recurring transactions
have been appended. This ensures the recurring transactions are
positioned by date. Note: the positions of non-recurring
transactions will probably be affected."
 :tag "dklrt-SortAfterAppend"
 :type '(boolean))

(defcustom dklrt-PythonProgram "python"
 "The Python interpreter to be run.
The default assumes python is on the PATH."
 :tag "dklrt-PythonProgram"
 :type '(string))

(defcustom dklrt-AppendBefore "1d"
 "Controls when a recurring transaction is actually appended.
The value is a period do list format: <integer><y|m|d|w|h>. A
recurring transaction is appended when the current date/time is
greater than or equal to the configured transaction date minus
the specified period. If nil or empty, the recurring transaction
is appended without anticipation on or after the configured
transaction date."
 :tag "dklrt-AppendBefore"
 :type '(string))

(defcustom dklrt-RecurringConfigFileSuffix "rec"
 "Suffix of Recurring Transactions Config File (excluding period)."
 :tag "dklrt-RecurringConfigFileSuffix"
 :type '(string))

(defconst dklrt-PackageDirectory
 (if load-file-name
  (file-name-directory load-file-name)
  nil))

; Hard-coded alternative value for debug only.
(or dklrt-PackageDirectory 
 (setq dklrt-PackageDirectory (concat (getenv "rel"))))

;;;###autoload
(defun dklrt-SetCcKeys()
 "Bind \C-cr to `dklrt-AppendRecurring'.
To invoke, add this function to `ledger-mode-hook'."
 (define-key (current-local-map) "\C-cr" 'dklrt-AppendRecurring))

;;;###autoload
(defun dklrt-AppendRecurringMaybe()
 "Call `dklrt-AppendRecurring', but only if appropriate."
 (interactive)
 (if (dklrt-AppendRecurringOk) (dklrt-AppendRecurring)))

;;;###autoload
(defun dklrt-AppendRecurring()
 "Append recurring transactions to the current ledger buffer/file."
 (interactive)
 (dklrt-AppendRecurringOk t)

 (message "Appending recurring transactions...")
 (let*
  ((Lfn (buffer-file-name))
   (Cfn (dklrt-RecurringConfigFileName Lfn))
   (Pfn (expand-file-name "Recurring.py" dklrt-PackageDirectory))
   (AppendBefore
    (if (> (length dklrt-AppendBefore) 0) dklrt-AppendBefore "0h"))
   (Td (dkmisc-TimeApplyShift (dkmisc-DateTimeToText) AppendBefore))
   (Sc (format "\"%s\" \"%s\" \"%s\" \"%s\"  \"%s\""
    dklrt-PythonProgram Pfn Lfn Td Cfn)))

   (message "Invoking: \"%s\"..." Sc)
   (let*
    ((Fl (point-max))
     (So (shell-command-to-string Sc)))

    ; Check for error.
    (and (> (length So) 0) (error So))

    ; Sync buffer with (possibly) altered file.
    ; NB: Suppress mode reinitialisation to avoid infinite loop.
    (revert-buffer t t t)
    
    ; Transactions were appended?
    (if (> (point-max) Fl)
     (progn
      (if dklrt-SortAfterAppend
       (progn
        (message "Sorting buffer transactions by date...")
        (ledger-sort-buffer)))

      (message "Saving ledger buffer...") 
      (save-buffer))))))

;;;###autoload
(defun dklrt-AppendRecurringOk(&optional Throw)
 "Return non nil if ok to append recurring transactions.
The current buffer must be unmodified, in `ledger-mode', and a
Recurring Transactions Config File must exist for the current
ledger file. If THROW, call error() instead of returning nil."
 (and
  (dklrt-IsLedgerMode Throw)
  (dklrt-NotRecurringConfigFile Throw)
  (dklrt-Unmodified Throw)
  (dklrt-LedgerFileExists Throw)
  (dklrt-RecurringConfigFileExists Throw)))

;;;###autoload
(defun dklrt-IsLedgerMode(&optional Throw)
 "Return t if current buffer is a ledger buffer.
If THROW, call `error' instead of returning nil."
 (let*
  ((Rv (equal mode-name "Ledger")))
 (and (not Rv) Throw
  (error "Current buffer is not in ledger mode!"))
  Rv))

(defun dklrt-NotRecurringConfigFile(&optional Throw)
 "Return t if current buffer is not a Recurring Config File.
If THROW, call `error' instead of returning nil."
 (let*
  ((Fne (file-name-extension (buffer-file-name)))
   (Rv (not (string= Fne dklrt-RecurringConfigFileSuffix))))

  (and (not Rv) Throw
   (error "Cannot append recurring transactions to Config File!"))
  Rv))

(defun dklrt-Unmodified(&optional Throw)
 "Return t if current buffer is unmodified.
If THROW, call `error' instead of returning nil."
 (let*
  ((Rv (not (buffer-modified-p))))
  (and (not Rv) Throw
   (error "Current buffer has changed! Please save it first!"))
  Rv))

(defun dklrt-LedgerFileExists(&optional Throw)
 "Return t if the ledger file exists.
If THROW, call `error' instead of returning nil."
 (let*
  ((Lfn (buffer-file-name))
   (Rv (and Lfn (file-exists-p Lfn))))
  (and (not Rv) Throw
   (error "No such Ledger File: \"%s\"!" Lfn))
  Rv))

(defun dklrt-RecurringConfigFileExists(&optional Throw)
 "Return t if the Recurring Config File exists.
If THROW, call `error' instead of returning nil."
 (let*
  ((Lfn (buffer-file-name))
   (Cfn (dklrt-RecurringConfigFileName Lfn))
   (Rv (and Cfn (file-exists-p Cfn))))
  (and (not Rv) Throw
   (error "No such Recurring Config File: \"%s\"!" Cfn))
  Rv))

(defun dklrt-RecurringConfigFileName(LedgerFileName)
 "Return the corresponding recurring configuration file name.
Remove the suffix (if any) from LEDGERFILENAME and then append
the recurring suffix as configured via
`dklrt-RecurringConfigFileSuffix'."
 (concat (file-name-sans-extension LedgerFileName) "."
  dklrt-RecurringConfigFileSuffix))

(provide 'dklrt)