Código de ejemplo de generación de un PDF a partir de un board de Trello. En este caso https://trello.com/b/NoiWfLdi/trello-backend-example-public

trello-to-pdf.Rmd

---
title: "Trello to PDF"
author: "jrosell"
date: "2020-07-28"
output: pdf_document
---

## R Markdown

This is an R Markdown document. It gets Trello cards and its attachments from specific list on a public board and build a PDF document from it.

You can do it yourself by opening this file on RStudio and click the **Knit** button.

For this example, [$\text{\underline{this board}}$](https://trello.com/b/NoiWfLdi/trello-backend-example-public) is used.

## R code

```{r setup, results='hide',warning = FALSE, message = FALSE}
knitr::opts_chunk$set(warning = FALSE, message = FALSE)
if(!require(knitr)) install.packages("knitr")
if(!require(rmarkdown)) install.packages("rmarkdown")
if(!require(tidyverse)) install.packages("tidyverse")
library(jsonlite)
library(knitr)
library(rmarkdown)

trello_board_url <- "https://trello.com/b/NoiWfLdi/trello-backend-example"
json <- URLencode(paste(trello_board_url, ".json", sep = ""))

trello <- fromJSON(json)
cards <- trello$cards
attachments <- list()
for(i in seq_along(cards$attachments)){
  if(length(cards$attachments[[i]])>0){
    row <- list(
      attachment_id = cards$attachments[[i]]$id,
      attachment_url = cards$attachments[[i]]$url,
      attachment_basename = basename(cards$attachments[[i]]$url)
    )
    attachments <- append(attachments, list(row))
  }
}
attachments <- attachments %>% bind_rows(.id = 'id') %>% select(-id)
map2(.x = attachments$attachment_url, 
     .y = attachments$attachment_basename, 
     .f = ~download.file(.x, .y, mode="wb"))

```

# Published list

```{r cards, results='asis'}
output <- cards %>% 
  select(name, desc, idList, closed, url, idAttachmentCover) %>%
  filter(idList == "5f2027680adc692cac5e2fe8", !closed) %>%
  left_join(attachments, c("idAttachmentCover" = "attachment_id")) %>%
  mutate(
    markdown = paste('\n## ', name, '\n',
      desc, '\n\n![', idAttachmentCover, '](', attachment_basename, ')\n\n', sep = ""),
  ) %>% 
  select(markdown) %>% 
  unlist()

cat(output)
```

Here the output of this example: https://drive.google.com/file/d/1qJfbmpyWFoJQ8UjuBY6hkd7vgqKbDmGY/view?usp=sharing