Start on shell variables

README.md

@@ -307,8 +307,11 @@ Now everytime you create a title with "exercise" or any of the other words in
 that list _somewhere_ in the title, it will populate the note with the content
 of `XDG_DATA_HOME/jn/gym-measurements.md`.
 
+
 #### Template variables
 
+##### Predefined variables
+
 You can use predefined template variables in your templates.
 
 For example, a template consiting of
@@ -336,6 +339,30 @@ Note that template variables are very fresh, so there aren't many...
 
 If you have any suggestions on useful ones, raise an issue.
 
+##### Shell variables
+
+Another more powerful (and dangerous/fun) type of template variable is the
+shell variable.
+
+This allows you to shell out and fill the template with results of the shell
+command.
+
+Shell template variables start with `{%` and end with `%}`. 
+
+For example we can do:
+
+```
+The year is {% date +%Y %}.
+
+Hello {% echo 'Joe' %} And hello {% echo 'Jim' %}. 
+Here is a list of my files {% ls %}. 
+I hope you like them {% echo 'Joe' %}. 
+
+Written on {{ today }}.
+```
+
+The onus is on you to write the command correctly. It not working is undefined behaviour.
+
 
 #### Editing a template
 

src/templates/templates.nim

@@ -3,7 +3,7 @@
 
 import std/[os, parsecfg, paths, re, strutils]
 import ../config
-import ./variables/[today, note as noteV]
+import ./variables/[today, note as noteV, shell]
 
 
 type Template* = object
@@ -35,12 +35,13 @@ proc getTemplates*(config: Config): seq[Template] {.raises: [KeyError].} =
 
   return templates
 
-proc renderVariables*(templateContent: string, note: Path): string {.raises: [RegexError] .} =
-  var templateContent = templateContent.replace(re"{{\s*today\s*}}", today.process(note))
-  templateContent = templateContent.replace(re"{{\s*note\s*}}", noteV.process(note))
-  return templateContent
+proc renderVariables*(templateContent: string, note: Path): string {.raises: [RegexError, OSError, IOError] .} =
+  var content = templateContent.replace(re"{{\s*today\s*}}", today.process(note))
+  content = content.replace(re"{{\s*note\s*}}", noteV.process(note))
+  content = shell.process(content, note)
+  return content
 
-proc process*(myTemplate: Template, note: Path, config: Config) {.raises: [KeyError, IOError, RegexError].} =
+proc process*(myTemplate: Template, note: Path, config: Config) {.raises: [KeyError, OSError, IOError, RegexError].} =
   let templatePath = getTemplateLocation(config) / myTemplate.location
   let templateContent: string = getContent(templatePath)
 

src/templates/variables/shell.nim

@@ -0,0 +1,16 @@
+import std/[osproc, paths, re, strutils]
+
+let pattern = re"{%\s*(.+?)\s*%}"
+
+proc process*(templateContent: string, note: Path): string {.raises: [RegexError, OSError, IOError] .} =
+  result = templateContent
+
+  var matches = result.findAll(pattern)
+
+  while matches.len > 0:
+    let match = matches[0]
+    let command = match.replace(re"{%\s*|\s*%}", "").strip()
+    let output = execProcess(command).strip()
+    result = result.replace(match, output)
+    matches = result.findAll(pattern)
+

tests/data/templates/test-template-with-multiple-shell-variables.md

@@ -0,0 +1 @@
+Hello, {% echo 'Joe' %} and hello, {% echo 'Jebediah' %}.

tests/data/templates/test-template-with-shell-variable.md

@@ -0,0 +1 @@
+Hello, {% echo 'Joe' %}.

tests/test_templates.nim

@@ -61,3 +61,27 @@ suite "Template tests":
     )
 
     check(expected in actual)
+
+  test "It renders shell variables":
+    let expected = "Hello, Joe.\n"
+
+    let actual = renderVariables(
+      getContent(
+        Path("./tests/data/templates/test-template-with-shell-variable.md")
+      ),
+      Path("Does not matter")
+    )
+
+    check(expected == actual)
+
+  test "It renders multiple shell variables":
+    let expected = "Hello, Joe and hello, Jebediah.\n"
+
+    let actual = renderVariables(
+      getContent(
+        Path("./tests/data/templates/test-template-with-multiple-shell-variables.md")
+      ),
+      Path("Does not matter")
+    )
+
+    check(expected == actual)