#lang racket/base

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;; Tracking current and historical references to uploaded files.
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(require db
         racket/string)

(provide replace-current-attachment-references!
         record-version-attachment-references!
         rebuild-attachment-references!)

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;; Supporting functions
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(define (attachment-rows db)
  (query-rows db
              #<<SQL
SELECT a.id, p.slug, a.stored_name, p.namespace
FROM attachments a
JOIN pages p ON p.id = a.page_id
ORDER BY a.id
SQL
              ))

(define (attachment-url slug stored-name)
  (format "/uploads/~a/~a" slug stored-name))

(define (record-references! db page-id page-version-id markdown current? referenced-at)
  (for ((row (in-list (attachment-rows db))))
    (define attachment-id (vector-ref row 0))
    (define slug (vector-ref row 1))
    (define stored-name (vector-ref row 2))
    (define namespace (vector-ref row 3))
    (define reference (if (string=? namespace "") slug (string-append namespace ":" slug)))
    (define current-url (attachment-url reference stored-name))
    (define legacy-url (attachment-url slug stored-name))
    (when (or (string-contains? markdown current-url)
              (and (not (string=? namespace ""))
                   (string-contains? markdown legacy-url)))
      (query-exec db
                  #<<SQL
INSERT INTO attachment_references
       (attachment_id, page_id, page_version_id, current_reference, referenced_at)
VALUES ($1, $2, $3, $4, $5)
SQL
                  attachment-id
                  page-id
                  page-version-id
                  current?
                  referenced-at))))

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;; Provided functions
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; goal   : Replace the current attachment references for one page.
; pre    : page-id identifies a page and markdown is its new current source.
; post   : Current-reference rows for the page reflect markdown exactly.
; result : void.
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(define (replace-current-attachment-references! db page-id markdown referenced-at)
  (query-exec db
              "DELETE FROM attachment_references WHERE page_id = $1 AND current_reference = TRUE"
              page-id)
  (record-references! db page-id sql-null markdown #t referenced-at)
  (void))

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; goal   : Record attachment references present in an immutable page version.
; pre    : page-version-id identifies the stored version represented by markdown.
; post   : Historical-reference rows for that version reflect markdown exactly.
; result : void.
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(define (record-version-attachment-references! db page-id page-version-id markdown referenced-at)
  (query-exec db
              "DELETE FROM attachment_references WHERE page_version_id = $1 AND current_reference = FALSE"
              page-version-id)
  (record-references! db page-id page-version-id markdown #f referenced-at)
  (void))

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; goal   : Rebuild all attachment references from current pages and page history.
; pre    : attachment_references and the existing wiki tables are available.
; post   : The reference table reflects every current and historical Markdown page.
; result : void.
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(define (rebuild-attachment-references! db)
  (query-exec db "DELETE FROM attachment_references")
  (for ((row (in-list
              (query-rows db
                          "SELECT id, markdown, updated_at FROM pages WHERE archived = FALSE"))))
    (replace-current-attachment-references! db
                                            (vector-ref row 0)
                                            (vector-ref row 1)
                                            (vector-ref row 2)))
  (for ((row (in-list
              (query-rows db
                          "SELECT id, page_id, markdown, created_at FROM page_versions ORDER BY id"))))
    (record-version-attachment-references! db
                                           (vector-ref row 1)
                                           (vector-ref row 0)
                                           (vector-ref row 2)
                                           (vector-ref row 3)))
  (void))