From 884afe538a5de60fd5638a87620d3cfa00d90f6f Mon Sep 17 00:00:00 2001
From: Paul Duncan <pabs@pablotron.org>
Date: Sun, 6 Mar 2016 19:17:22 -0500
Subject: add templates

---
 src/guff/template-cache.cr | 12 +++++++++
 src/guff/template-token.cr | 21 +++++++++++++++
 src/guff/template.cr       | 66 ++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 99 insertions(+)
 create mode 100644 src/guff/template-cache.cr
 create mode 100644 src/guff/template-token.cr
 create mode 100644 src/guff/template.cr

diff --git a/src/guff/template-cache.cr b/src/guff/template-cache.cr
new file mode 100644
index 0000000..7a20179
--- /dev/null
+++ b/src/guff/template-cache.cr
@@ -0,0 +1,12 @@
+module Guff
+  class TemplateCache
+    def initialize(@templates : Hash(Symbol, String))
+      @cache = {} of Symbol => Template
+    end
+
+    def [](key : Symbol) : Template
+      raise "unknown template: #{key}" unless @templates[key]?
+      @cache[key] ||= Template.new(@templates[key])
+    end
+  end
+end
diff --git a/src/guff/template-token.cr b/src/guff/template-token.cr
new file mode 100644
index 0000000..04e8f11
--- /dev/null
+++ b/src/guff/template-token.cr
@@ -0,0 +1,21 @@
+module Guff
+  class TemplateToken
+    getter :type
+
+    def initialize(@type : Symbol, @val : String)
+    end
+
+    def get(args : Hash(String, String))
+      case @type
+      when :key
+        raise "missing key: #{@val}" unless args.has_key?(@val)
+        args[@val]
+      when :val
+        @val
+      else
+        # never reached
+        raise "unknown token type: #{@type}"
+      end
+    end
+  end
+end
diff --git a/src/guff/template.cr b/src/guff/template.cr
new file mode 100644
index 0000000..01a4c86
--- /dev/null
+++ b/src/guff/template.cr
@@ -0,0 +1,66 @@
+module Guff
+  class Template
+    getter :string
+
+    def initialize(@string : String)
+      @tokens = scan(@string)
+      @has_keys = @tokens.select { |t| t.type == :key }.size > 0
+    end
+
+    def run(args = nil : Hash(String, String)?) : String
+      if @has_keys
+        # check template args
+        if args || args.size == 0
+          raise "missing template args: %s" % [@tokens.select { |t| 
+            t.type == :key
+          }.join(", ")]
+        end
+
+        # build result
+        String.builder do |r|
+          @tokens.each do |t|
+            r << t.get(args)
+          end
+        end
+      else
+        # no keys, return literal string
+        @string
+      end
+    end
+
+    SCAN_RE = %r{
+      # match key
+      (?:%\{(?<key>[^\}]+)\})
+
+      |
+
+      # match literal value
+      (?<val>[^%]+)
+
+      |
+
+      # match literal percent
+      (?<pct>%)
+    }mx
+
+    private def scan(s : String)
+      r = [] of TemplateToken
+
+      s.scan(SCAN_RE) do |md|
+        if md["key"]?
+          r << TemplateToken.new(:key, md["key"].strip)
+        elsif md["val"]?
+          r << TemplateToken.new(:val, md["val"])
+        elsif md["pct"]?
+          r << TemplateToken.new(:val, "%")
+        else
+          # never reached
+          raise "unknown match: #{md}"
+        end
+      end
+
+      # return result
+      r
+    end
+  end
+end
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