#lang racket
(require xml/path)
(require "world.rkt" "tools.rkt" "map.rkt")
(require racket/rerequire)

; hash of mod-dates takes lists of paths as keys,
; and lists of modification times as values.
; Reason: a templated page is a combination of two source files.
; Because templates have a one-to-many relationship with source files,
; Need to track template mod-date for each source file.
; Otherwise a changed template will get reloaded only once, 
; and after that get reported as being up to date.
; Possible: store hash on disk so mod records are preserved 
; between development sessions (prob a worthless optimization)
(define mod-dates (make-hash))

(define (mod-date . paths) 
  (set! paths (flatten paths))
  (when (andmap file-exists? paths)
    (map file-or-directory-modify-seconds paths)))

(define (log-refresh . paths)
  (set! paths (flatten paths))
  (hash-set! mod-dates paths (mod-date paths)))

(define (source-needs-refresh? . paths)
  (set! paths (flatten paths))
  (or (not (in? mod-dates paths))  ; no mod date
      (not (equal? (mod-date paths) (get mod-dates paths))))) ; data changed

; when you want to generate everything fresh, but not force everything
(define (reset-mod-dates)
  (let [(keys (hash-keys mod-dates))]
    (map (λ(k) (hash-remove mod-dates k)) keys)))

; helper functions for regenerate functions
(define pollen-file-root (current-directory))

(define (regenerate-file f)
  (let ([path (build-path pollen-file-root f)])
    (displayln (format "Regenerating: ~a" f))
    (regenerate path)))

;; todo: maybe move this tools.rkt as a utility
(define (filename-of path)
  (let-values ([(dir filename ignored) (split-path path)])
    filename))

(define (regenerate-pmap-pages pmap)
  (define pmap-sequence 
    (make-page-sequence (main->tree (dynamic-require pmap 'main))))
  (displayln (format "Regenerating pages from pollen map: ~a" (filename-of pmap)))
  (for-each regenerate-file pmap-sequence))

(define (get-pollen-files-with-ext ext)
  (filter (λ(f) (has-ext? f ext)) (directory-list pollen-file-root)))

; burn all files
(define (regenerate-all-files)
  (reset-mod-dates)
  
  (define all-preproc-files (get-pollen-files-with-ext POLLEN_PREPROC_EXT))
  (for-each regenerate-file all-preproc-files)
  
  (define all-pollen-maps (get-pollen-files-with-ext POLLEN_MAP_EXT))
  (for-each regenerate-pmap-pages all-pollen-maps)
  
  (displayln "Completed"))



(define (regenerate path #:force [force #f])
  ; dispatches path-in to the right place
  
  
  (let ([path (->complete-path path)])
    (cond
      [(needs-preproc? path) (do-preproc path #:force force)]
      [(needs-template? path) (do-template path #:force force)]
      [(pmap-source? path) (regenerate-pmap-pages path)])))



(define (regenerate-message path)
  (message "Regenerated:" (->string (file-name-from-path path))))

(define (do-preproc path #:force [force #f])
  ; set up preproc-in-path & preproc-out-path values
  (let-values 
      ([(preproc-in-path preproc-out-path) 
        (if (preproc-source? path) 
            (values path (make-preproc-out-path path))
            (values (make-preproc-in-path path) path))])    
    
    (when (and (file-exists? preproc-in-path) 
               (or force
                   (not (file-exists? preproc-out-path))
                   (source-needs-refresh? preproc-in-path)))
      (log-refresh preproc-in-path)
      ; use single quotes to escape spaces in pathnames
      (define command 
        (format "~a '~a' > '~a'" RACKET_PATH preproc-in-path preproc-out-path))
      ; discard output using open-output-nowhere
      (parameterize ([current-output-port (open-output-nowhere)])
        (system command))
      (regenerate-message preproc-out-path))))


(define (do-template path [template-name empty] #:force [force #f]) 
  ; take full path or filename
  ; return full path of templated file
  
  (define source-path (->complete-path 
                       (if (pollen-source? path) 
                           path
                           (make-pollen-source-path path))))
  
  (define-values (source-dir source-name ignored) (split-path source-path))
  
  ; get body out of source file (to retrieve template name)
  ; use dynamic-rerequire to force refresh for dynamic-require, 
  ; otherwise it will cache
  ; parameterize needed because source files have relative requires
  (define file-was-reloaded-port (open-output-string))
  (parameterize ([current-directory source-dir]
                 [current-error-port file-was-reloaded-port])
    ; by default, rerequire reports reloads to error port.
    ; so capture this message to find out if anything was reloaded.
    (dynamic-rerequire source-path))
  
  (define file-was-reloaded? 
    (> (string-length (get-output-string file-was-reloaded-port)) 0))
  
  ; set template, regenerate, get data
  ; first, if no template name provided, look it up
  (when (or (empty? template-name) (not (file-exists? (build-path source-dir template-name))))
    ; get template name out of meta fields.
    ; todo: template file in body may not refer to a file that exists.
    ; todo: consider whether file-was-reloaded could change metas
    ; (because here, I'm retrieving them from existing source)
    
    ;;;;;;;;;;;;;;
    ;; todo: next
    ;;;;;;;;;;;;;;
    
    (define metas (dynamic-require source-path 'metas))
    (set! template-name (if (TEMPLATE_META_KEY . in? . metas)
                            (get metas TEMPLATE_META_KEY)
                            DEFAULT_TEMPLATE)))
  (define template-path (build-path source-dir template-name))
  ; refresh template (it might have its own p file)
  (regenerate template-path #:force force)
  
  ; calculate new path for generated file: 
  ; base from source + ext from template
  (define generated-path (build-path source-dir (add-ext (remove-ext source-name) (get-ext template-path))))
  
  ; do we need to refresh?
  (when (or force
            (not (file-exists? generated-path)) 
            (source-needs-refresh? source-path template-path)
            file-was-reloaded?)
    (log-refresh source-path template-path)
    
    ; Templates are part of the compile operation.
    ; Therefore no way to arbitrarily invoke template at run-time.
    ; This routine creates a new namespace and compiles the template within it.
    ; Todo: performance improvement would be to make a macro
    ; that pre-compiles all known templates into their own functions.
    ; then apply-template can either look for one of those functions,
    ; if the template exists,
    ; or if not found, use the eval technique.
    (define page-result
      ; parameterize current-directory to make file requires work
      (parameterize ([current-namespace (make-base-empty-namespace)]
                     [current-directory source-dir]
                     [current-output-port (open-output-nowhere)])
        (namespace-require 'racket) ; use namespace-require for FIRST require, then eval after
        (eval '(require (planet mb/pollen/template)) (current-namespace))
        ; import source into eval space, 
        ; automatically sets up main & metas & here
        (eval `(require ,(path->string source-name)) (current-namespace)) 
        (eval `(include-template #:command-char ,TEMPLATE_FIELD_DELIMITER ,template-name) (current-namespace))))
    
    
    (display-to-file #:exists 'replace page-result generated-path)
    (regenerate-message generated-path)))


(provide regenerate regenerate-all-files)