Add Templates button to load common regex patterns

NEWS.md

 ## regexplain 0.1.x
 
+### 0.1.6
+
+* Added "Templates" button that opens a dialog to import regex patterns
+  (initially) sourced from <https://projects.lukehaas.me/regexhub>.
+* Added "Introduction", "Try These Examples" and "Resources" tabs to
+  the standard gadget Help tab.
+* Several bugfixes and tests were added around unicode character escaping within the gadget.
+
 ### 0.1.5
 
 * Options from **Regex** tab are extended to **Output** tab as well. Colored

R/regex_gadget.R

             flex = c(1, 3),
             fillCol(
               flex = c(1, 1),
-              textInputCode('pattern', 'RegEx', width = "100%",
-                            placeholder = "Standard RegEx, e.g. \\w+_\\d{2,4}\\s+"),
+              fillRow(
+                flex = c(5, 1),
+                textInputCode('pattern', 'RegEx', width = "100%",
+                              placeholder = "Standard RegEx, e.g. \\w+_\\d{2,4}\\s+"),
+                tags$div(style = "margin-top: 23px; margin-left:6px;",
+                         actionButton("show_templates", "Templates", class = "btn-success"))
+              ),
               checkboxGroupInput(
                 'regex_options',
                 label = HTML(
       toHTML(paste(error_message, warning_message, res))
     })
 
+    # ---- Server - Tab - RegEx - Templates ----
+    templates <- get_templates()
+
+    this_template <- reactive({
+      req(input$template)
+      purrr::keep(templates, ~ .$name == input$template) %>%
+        purrr::flatten()
+    })
+
+    observeEvent(input$show_templates, {
+      showModal(
+        modalDialog(
+          title = "Templates",
+          footer = tagList(
+            modalButton("Cancel"),
+            actionButton("apply_template", "Use Template", class = "btn-success")
+          ),
+          selectInput("template", "Template",
+                      choices = c("Choose template" = "",
+                                  purrr::set_names(purrr::map_chr(templates, 'name')))),
+          uiOutput("template_info")
+        )
+      )
+    })
+
+    output$template_info <- renderUI({
+      req(this_template())
+      tagList(
+        tags$h5("Description"),
+        tags$p(this_template()$description),
+        tags$h5("Pattern"),
+        tags$pre(
+          tags$code(
+            this_template()$regex
+          )
+        )
+      )
+    })
+
+    observeEvent(input$apply_template, {
+      updateTextInput(session, "pattern", value = this_template()$regex)
+      updateSelectInput(session, "template", selected = "")
+      removeModal()
+    })
+
     # ---- Server - Tab - Output ----
     regexFn_replacement_val <- NULL
 
     )
   } else return(NULL)
 }
+
+#' Loads Regex Pattern Templates
+#'
+#' Sourced from [Regex Hub](https://projects.lukehaas.me/regexhub)
+#' and available at <https://github.com/lukehaas/RegexHub>. Copyright
+#' Luke Haas licensed under the MIT license available at
+#' <https://github.com/lukehaas/RegexHub/commit/3ab87b5a4fd2817b42e2e45dcf040d4f0164ea37>.
+#'
+#' @keywords internal
+get_templates <- function() {
+  if (!requireNamespace("jsonlite")) {
+    warning("Please install the `jsonlite` package to use template features")
+    return(NULL)
+  }
+  f_patterns <- system.file("extdata", "patterns.json", package = "regexplain")
+  if (!file.exists(f_patterns)) return(NULL)
+  jsonlite::fromJSON(f_patterns, simplifyVector = FALSE, simplifyDataFrame = FALSE, simplifyMatrix = FALSE)
+}

extdata/patterns.json

+[{
+	"name":"Date in format dd/mm/yyyy",
+	"regex":"^(0?[1-9]|[12][0-9]|3[01])([ /\\\\-])(0?[1-9]|1[012])\\\\2([0-9][0-9][0-9][0-9])(([ -])([0-1]?[0-9]|2[0-3]):[0-5]?[0-9]:[0-5]?[0-9])?$",
+	"description":"Will match dates with dashes, slashes or with spaces (e.g. dd-mm-yyyy dd/mm/yyyy dd mm yyyy), and optional time separated by a space or a dash (e.g. dd-mm-yyyy-hh:mm:ss or dd/mm/yyyy hh:mm:ss).",
+	"tags":"date,time"
+},
+{
+	"name":"Time in 24-hour format",
+	"regex":"^([01]?[0-9]|2[0-3]):[0-5][0-9]$",
+	"description": "Match times in 24 hour format",
+	"tags":"date,time"
+},
+{
+	"name":"Date and time in ISO-8601 format",
+	"regex":"^(?![+-]?\\\\d{4,5}-?(?:\\\\d{2}|W\\\\d{2})T)(?:|(\\\\d{4}|[+-]\\\\d{5})-?(?:|(0\\\\d|1[0-2])(?:|-?([0-2]\\\\d|3[0-1]))|([0-2]\\\\d{2}|3[0-5]\\\\d|36[0-6])|W([0-4]\\\\d|5[0-3])(?:|-?([1-7])))(?:(?!\\\\d)|T(?=\\\\d)))(?:|([01]\\\\d|2[0-4])(?:|:?([0-5]\\\\d)(?:|:?([0-5]\\\\d)(?:|\\\\.(\\\\d{3})))(?:|[zZ]|([+-](?:[01]\\\\d|2[0-4]))(?:|:?([0-5]\\\\d)))))$",
+	"description": "Will match a valid date and times in the ISO-8601 format, excludes durations.",
+	"tags": "date,time"
+},
+{
+	"name":"HTML tags",
+	"regex":"^<([a-z1-6]+)([^<]+)*(?:>(.*)<\\\\/\\\\1>| *\\\\/>)$",
+	"description":"Match opening and closing HTML tags with content between",
+	"tags":"markup,xml,html"
+},
+{
+	"name":"Username",
+	"regex":"^[a-zA-Z0-9_-]{3,16}$",
+	"description":"A string between 3 and 16 characters, allowing alphanumeric characters and hyphens and underscores",
+	"tags":"username,validation"
+},
+{
+	"name":"Hex Color Value",
+	"regex":"^#?([a-fA-F0-9]{6}|[a-fA-F0-9]{3})$",
+	"description":"RGB hex colors",
+	"tags":"hex,color"
+},
+{
+	"name":"URL Slug",
+	"regex":"^[a-z0-9-]+$",
+	"description":"Match valid URL slugs",
+	"tags":"URL"
+},
+{
+	"name":"Email",
+	"regex":"^.+@.+$",
+	"description":"Verify that there is an @ symbol with something before it",
+	"tags":"email,validation"
+},
+{
+	"name":"SRC of image tag",
+	"regex":"^<\\s*img[^>]+src\\s*=\\s*([\"'])(.*?)\\1[^>]*>$",
+	"description":"Match the src attribute of an HTML image tag",
+	"tags":"html,tag,image"
+},
+{
+	"name":"URL",
+	"regex":"^((https?|ftp|file):\\/\\/)?([\\da-z\\.-]+)\\.([a-z\\.]{2,6})([\\/\\w \\.-]*)*\\/?$",
+	"description":"Match URL with optional protocol",
+	"tags":"url,address,http"
+},
+{
+	"name":"IPv4 Address",
+	"regex":"^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$",
+	"description":"Match IP v4 addresses",
+	"tags":"tcpip,internet,address"
+},
+{
+	"name":"IPv6 Address",
+	"regex":"^(([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]))$",
+	"description": "Match IP v6 addresses",
+	"tags":"tcpip,internet,address"
+},
+{
+	"name":"JWT",
+	"regex":"^[A-Za-z0-9-_=]+\\.[A-Za-z0-9-_=]+\\.?[A-Za-z0-9-_.+/=]*$",
+	"description": "JSON Web Token (encoded)",
+	"tags":"www"
+},
+{
+	"name":"Positive Integer",
+	"regex":"^\\d+$",
+	"description":"Match whole numbers above zero",
+	"tags":"number"
+},
+{
+	"name":"Negative Integer",
+	"regex":"^-\\d+$",
+	"description":"Match whole numbers below zero",
+	"tags":"number"
+},
+{
+	"name":"Integer",
+	"regex":"^-?\\d+$",
+	"description":"Match whole numbers, above or below zero",
+	"tags":"number"
+},
+{
+	"name":"Positive number",
+	"regex":"^\\d*\\.?\\d+$",
+	"description":"Match integers or floats that are positive",
+	"tags":"float"
+},
+{
+	"name":"Negative number",
+	"regex":"^-\\d*\\.?\\d+$",
+	"description":"Match integers or floats that are negative",
+	"tags":"float"
+},
+{
+	"name":"Positive or negative number",
+	"regex":"^-?\\d*\\.?\\d+$",
+	"description":"Match integers or floats that are positive or negative",
+	"tags":"float"
+},
+{
+	"name":"Phone number",
+	"regex":"^\\+?(\\d.*){3,}$",
+	"description":"Match phone numbers at least 3 digits long",
+	"tags":"validation"
+},
+{
+	"name":"New line",
+	"regex":"[\\r\\n]|$",
+	"description":"Match new lines within text",
+	"tags":"text"
+},
+{
+	"name":"ID of Youtube video",
+	"regex":"https?:\\/\\/(?:youtu\\.be\\/|(?:[a-z]{2,3}\\.)?youtube\\.com\\/watch(?:\\?|#\\!)v=)([\\w-]{11}).*/gi",
+	"description":"Match the ID of a youtube video URL",
+	"tags":"video,youtube,url"
+},
+{
+	"name":"ID of Youtube Channel",
+	"regex":"https?:\\/\\/(www\\.)?youtube.com\\/channel\\/UC([-_a-z0-9]{22})/i",
+	"description":"Match the ID of a youtube channel URL",
+	"tags":"channel,youtube,url"
+},
+{
+	"name":"CSS comment",
+	"regex":"\\/\\*[^*]*\\*+([^/*][^*]*\\*+)*\\/",
+	"description":"Match standard CSS comments",
+	"tags":"css,comment,code"
+},
+{
+	"name":"Wordpress shortcodes",
+	"regex":"^\\[([a-z-_0-9]+)([^\\[]+)*(?:\\](.*)\\[\\/\\1\\]|\\s+\\/\\])$",
+	"description":"Matches opening and closing shortcode tags with content in-between them.",
+	"tags":"wordpress,shortcodes,markup"
+},
+{
+	"name":"U.S./Canadian ZIP/Postal Code",
+	"regex":"(^\\d{5}(-\\d{4})?$)|(^[ABCEGHJKLMNPRSTVXY]{1}\\d{1}[A-Z]{1} *\\d{1}[A-Z]{1}\\d{1}$)",
+	"description":"Matches US ZIP, ZIP+4, and Canadian Postal Codes",
+	"tags":"address, postal, zip"
+},
+{
+	"name":"UK Postal Code",
+	"regex":"^(([gG][iI][rR] {0,}0[aA]{2})|(([aA][sS][cC][nN]|[sS][tT][hH][lL]|[tT][dD][cC][uU]|[bB][bB][nN][dD]|[bB][iI][qQ][qQ]|[fF][iI][qQ][qQ]|[pP][cC][rR][nN]|[sS][iI][qQ][qQ]|[iT][kK][cC][aA]) {0,}1[zZ]{2})|((([a-pr-uwyzA-PR-UWYZ][a-hk-yxA-HK-XY]?[0-9][0-9]?)|(([a-pr-uwyzA-PR-UWYZ][0-9][a-hjkstuwA-HJKSTUW])|([a-pr-uwyzA-PR-UWYZ][a-hk-yA-HK-Y][0-9][abehmnprv-yABEHMNPRV-Y]))) {0,}[0-9][abd-hjlnp-uw-zABD-HJLNP-UW-Z]{2}))$",
+	"description":"Matches all UK postcodes",
+	"tags":"address, postal, zip"
+},
+{
+	"name":"Brazilian ZIP/Postal Code",
+	"regex":"^[0-9]{5}-[0-9]{3}$",
+	"description":"Matches BR ZIP/Postal Code",
+	"tags":"address, postal, zip"
+},
+{
+	"name":"Morse Code",
+	"regex":"^[.-]{1,5}(?:[ \\t]+[.-]{1,5})*(?:[ \\t]+[.-]{1,5}(?:[ \\t]+[.-]{1,5})*)*$",
+	"description":"Matches valid Morse Code",
+	"tags":"morse, code"
+},
+{
+	"name":"Image shortcode",
+	"regex":"\\[img\\](.*?)\\[\\/img\\]",
+	"description":"Matches the content in between [img][/img]. Useful for making dynamic WYSIWYG editors",
+	"tags":"img, shortcode, wysiwyg"
+}
+]