Lua: add function `pandoc.mediabag.make_data_uri`.

The function takes a MIME type and raw data from which it creates an
RFC 2397 data URI.

Closes: #10876

3 files changed, 68 insertions, 0 deletions

diff --git a/doc/lua-filters.md b/doc/lua-filters.md
index 9a29732d9..b2ad38ad5 100644
--- a/doc/lua-filters.md
+++ b/doc/lua-filters.md
@@ -4532,6 +4532,38 @@ Returns:
 
 *Since: 2.0*
 
+### make_data_uri {#pandoc.mediabag.make_data_uri}
+
+`make_data_uri (mime_type, raw_data)`
+
+Convert the input data into a data URI as defined by RFC 2397.
+
+Example:
+
+    -- Embed an unofficial pandoc logo
+    local pandoc_logo_url = 'https://raw.githubusercontent.com/'
+      .. 'tarleb/pandoc-logo/main/pandoc.svg'
+
+    local datauri = pandoc.mediabag.make_data_uri(
+      pandoc.mediabag.fetch(pandoc_logo_url)
+    )
+
+    local image = pandoc.Image('Logo', datauri)
+
+Parameters:
+
+`mime_type`
+:   MIME type of the data (string)
+
+`raw_data`
+:   data to encode (string)
+
+Returns:
+
+- data uri (string)
+
+*Since: 3.7.1*
+
 ### write {#pandoc.mediabag.write}
 
 `write (dir[, fp])`
diff --git a/pandoc-lua-engine/src/Text/Pandoc/Lua/Module/MediaBag.hs b/pandoc-lua-engine/src/Text/Pandoc/Lua/Module/MediaBag.hs
index 44957e246..da666779a 100644
--- a/pandoc-lua-engine/src/Text/Pandoc/Lua/Module/MediaBag.hs
+++ b/pandoc-lua-engine/src/Text/Pandoc/Lua/Module/MediaBag.hs
@@ -27,6 +27,7 @@ import Text.Pandoc.Lua.Marshal.List (pushPandocList)
 import Text.Pandoc.Lua.Orphans ()
 import Text.Pandoc.Lua.PandocLua (unPandocLua)
 import Text.Pandoc.MIME (MimeType)
+import Text.Pandoc.SelfContained (makeDataURI)
 
 import qualified Data.ByteString.Lazy as BL
 import qualified Data.Text as T
@@ -60,6 +61,7 @@ documentedModule = Module
       , items   `since` makeVersion [2,7,3]
       , list    `since` makeVersion [2,0]
       , lookup  `since` makeVersion [2,0]
+      , make_data_uri `since` makeVersion [3,7,1]
       , write   `since` makeVersion [3,0]
       ]
   , moduleOperations = []
@@ -243,6 +245,29 @@ fetch = defun "fetch"
   , "    local mt, contents = pandoc.mediabag.fetch(diagram_url)"
   ]
 
+make_data_uri :: DocumentedFunction PandocError
+make_data_uri = defun "make_data_uri"
+  ### (\mime raw -> pure $ makeDataURI (mime, raw))
+  <#> parameter Lua.peekText "string" "mime_type" "MIME type of the data"
+  <#> parameter Lua.peekByteString "string" "raw_data" "data to encode"
+  =#> functionResult Lua.pushText "string" "data uri"
+  #? T.unlines
+  [ "Convert the input data into a data URI as defined by RFC 2397."
+  , ""
+  , "Example:"
+  , ""
+  , "    -- Embed an unofficial pandoc logo"
+  , "    local pandoc_logo_url = 'https://raw.githubusercontent.com/'"
+  , "      .. 'tarleb/pandoc-logo/main/pandoc.svg'"
+  , ""
+  , "    local datauri = pandoc.mediabag.make_data_uri("
+  , "      pandoc.mediabag.fetch(pandoc_logo_url)"
+  , "    )"
+  , ""
+  , "    local image = pandoc.Image('Logo', datauri)"
+  ]
+
+
 -- | Extract the mediabag or just a single entry.
 write :: DocumentedFunction PandocError
 write = defun "write"
diff --git a/pandoc-lua-engine/test/lua/module/pandoc-mediabag.lua b/pandoc-lua-engine/test/lua/module/pandoc-mediabag.lua
index f001bf8db..39653cccc 100644
--- a/pandoc-lua-engine/test/lua/module/pandoc-mediabag.lua
+++ b/pandoc-lua-engine/test/lua/module/pandoc-mediabag.lua
@@ -104,4 +104,15 @@ return {
     end),
   },
 
+  group 'make_data_uri' {
+    test('returns a data URI', function ()
+      local uri = mediabag.make_data_uri('text/plain', 'foo')
+      assert.are_equal(uri:sub(1,5), 'data:')
+    end),
+    test('URI specifies the given MIME type', function ()
+      local mimetype = 'text/plain'
+      local uri = mediabag.make_data_uri(mimetype, 'foo')
+      assert.are_equal(uri:sub(6, 5 + #mimetype), mimetype)
+    end),
+  }
 }