feat(mermaid): improve cache management

Refs #14

R/mermaid.R

@@ -12,7 +12,9 @@
 #' @param diagram Diagram in mermaid markdown-like language or file (as a connection or file name) containing a diagram specification
 #' @param theme Mermaid theme (See https://mermaid.js.org/config/theming.html#available-themes)
 #' @param format Image format (either `"jpg"`, or `"png"`, or `"svg"`)
-#' @param file Path to the downloaded image
+#' @param file.dest Path to the downloaded image
+#' @param link Link generated by [mermaid_gen_link]
+#' @param server URL of the server used to generate the link
 #'
 #' @return The path to the downloaded image.
 #' @export
@@ -33,12 +35,13 @@
 mermaid <- function(diagram,
                     format = "png",
                     theme = "default",
-                    file = file.path(tempdir(), paste0(rlang::hash(diagram), ".", format))) {
-  if (!file.exists(file)) {
-    link <- mermaid_gen_link(diagram, theme = theme, format = format)
-    download.file(link, file, quiet = TRUE, mode = "wb")
+                    file.dest = file.path(tempdir(),
+                                          paste0(rlang::hash(link), ".", format)),
+                    link = mermaid_gen_link(diagram, theme = theme, format = format)) {
+  if (!file.exists(file.dest)) {
+    download.file(link, file.dest, quiet = TRUE, mode = "wb")
   }
-  return(file)
+  return(file.dest)
 }
 
 #' Compress data in pako format
@@ -65,7 +68,7 @@ return(compressed_data)
 
 #' @rdname mermaid
 #' @export
-mermaid_gen_link <- function(diagram, theme = "default", format = "png") {
+mermaid_gen_link <- function(diagram, theme = "default", format = "png", server = "https://mermaid.ink") {
   is_connection_or_file <- inherits(diagram[1], "connection") ||
     file.exists(diagram[1])
   if (is_connection_or_file) {
@@ -80,7 +83,7 @@ mermaid_gen_link <- function(diagram, theme = "default", format = "png") {
   deflated <- pako_deflate(jGraph)
   dEncode = gsub("\n", "", jsonlite::base64url_enc(deflated))
   mode <- ifelse(format != "svg", "img", "svg")
-  link = sprintf('https://mermaid.ink/%s/pako:%s', mode, dEncode)
+  link = sprintf("%s/%s/pako:%s", server, mode, dEncode)
   if (format != "svg") {
     link <- paste0(link, "?type=", format)
   }

man/mermaid.Rd

@@ -9,10 +9,16 @@ mermaid(
   diagram,
   format = "png",
   theme = "default",
-  file = file.path(tempdir(), paste0(rlang::hash(diagram), ".", format))
+  file.dest = file.path(tempdir(), paste0(rlang::hash(link), ".", format)),
+  link = mermaid_gen_link(diagram, theme = theme, format = format)
 )
 
-mermaid_gen_link(diagram, theme = "default", format = "png")
+mermaid_gen_link(
+  diagram,
+  theme = "default",
+  format = "png",
+  server = "https://mermaid.ink"
+)
 }
 \arguments{
 \item{diagram}{Diagram in mermaid markdown-like language or file (as a connection or file name) containing a diagram specification}
@@ -21,7 +27,11 @@ mermaid_gen_link(diagram, theme = "default", format = "png")
 
 \item{theme}{Mermaid theme (See https://mermaid.js.org/config/theming.html#available-themes)}
 
-\item{file}{Path to the downloaded image}
+\item{file.dest}{Path to the downloaded image}
+
+\item{link}{Link generated by \link{mermaid_gen_link}}
+
+\item{server}{URL of the server used to generate the link}
 }
 \value{
 The path to the downloaded image.

tests/testthat/test-mermaid.R

-test_that("Conversion of mmd to pako works", {
-  diagram <- "flowchart LR\n  A --> B"
+diagram <- "flowchart LR\n  A --> B"
+
+test_that("mermaid_gen_link: conversion of mmd to pako works", {
   pako <- "https://mermaid.ink/img/pako:eNqrVkrOT0lVslJKy8kvT85ILCpR8AmKyVNQcFTQ1bVTcFLSUcpNLcpNzExRsqpWKslIzQUpTklNSyzNKVGqrQUAjIcUfg?type=png"
+  # multiline string
   expect_equal(mermaid_gen_link(diagram), pako)
+  # character vector
   diagram <- strsplit(diagram, "\n")[[1]]
   expect_equal(mermaid_gen_link(diagram), pako)
+  # from file
+  f <- tempfile()
+  writeLines(diagram, f)
+  expect_equal(mermaid_gen_link(f), pako)
+})
+
+test_that("mermaid returns a file", {
+  f <- mermaid(diagram)
+  expect_true(file.exists(f))
 })