From a59630771f33c28f52cf947dc26a53e187d1252f Mon Sep 17 00:00:00 2001
From: Andinus <andinus@nand.sh>
Date: Tue, 28 Mar 2023 10:13:34 +0530
Subject: Add initial design, basic test

---
 lib/Template/Nest/Fast.rakumod | 111 +++++++++++++++++++++++++++++++++++++++++
 t/00-basic.rakutest            |   5 ++
 2 files changed, 116 insertions(+)
 create mode 100644 lib/Template/Nest/Fast.rakumod
 create mode 100644 t/00-basic.rakutest

diff --git a/lib/Template/Nest/Fast.rakumod b/lib/Template/Nest/Fast.rakumod
new file mode 100644
index 0000000..1b718ce
--- /dev/null
+++ b/lib/Template/Nest/Fast.rakumod
@@ -0,0 +1,111 @@
+#| Template::Nest::Fast is a high-performance template engine module
+#| for Raku, designed to process nested templates quickly and
+#| efficiently. This module improves on the original Template::Nest
+#| module by caching the index of positions of variables, resulting in
+#| significantly faster processing times.
+class Template::Nest::Fast {
+    # has Str @!token-delims = ['<!--%', '%-->'];
+    has Str $!name-label = 'TEMPLATE';
+    has IO $.template-dir is required;
+
+    # Template objects after compilation.
+    has %!templates;
+
+    #| TWEAK reads all the files in template-dir ending with '.html'
+    #| extension and compiles them.
+    submethod TWEAK() {
+        # Grab all files ending with .html recursively.
+        my IO @stack = $!template-dir, ;
+        my IO @templates = gather while @stack {
+            with @stack.pop {
+                when :d { @stack.append: .dir }
+                .take when .extension.lc eq 'html';
+            }
+        }
+
+        # Render all the files.
+        self.compile($_) for @templates;
+    }
+
+    #| compile reads a template and prepares it for render.
+    method compile(IO $template) {
+        # Get template name relative to $!template-dir and remove
+        # `.html` extension.
+        my Str $t = $template.relative($!template-dir).substr(0, *-5);
+
+        my Str $f = $template.slurp;
+
+        # Store the template path.
+        %!templates{$t}<path> = $template;
+
+        # Capture the start, end delim and the variable inside it. DO NOT
+        # backtrack.
+        with $f ~~ m:g/('<!--%'): \s*: (<[a..zA..Z0..9_-]>+): \s*: ('%-->'):/ -> @m {
+            # Initialize with an empty list.
+            %!templates{$t}<vars> = [];
+
+            # For every match we have start, end position of each
+            # delim and the variable.
+            #
+            # We sort @m by the start delim's position. (Does some
+            # magic, I have to comment it)
+            for @m.sort(*[0].from) -> $m {
+                # Store each variable alongside it's template file in
+                # %!templates.
+                push %!templates{$t}<vars>, %(
+                    name => ($m[1].Str),
+                    start-delim => ($m[0].from, $m[0].to),
+                    variable    => ($m[1].from, $m[1].to),
+                    end-delim   => ($m[2].from, $m[2].to),
+                    # Length of the string to replace.
+                    length      => ($m[2].to - $m[0].from),
+                );
+            }
+        }
+    }
+
+    #| parse consumes values of keys of the template object and
+    #| returns the final string that needs to be replaced with that
+    #| key.
+    #|
+    #| my %t = %( TEMPLATE => 'test', xyz => 'hi' )
+    #|
+    #| parse here consumes 'xyz' and returns 'hi', it can also handle
+    #| keys where the value is another Hash or a List.
+    method parse($var --> Str) {
+        given $var {
+            when Str  { return $var }
+            when Hash { return self.render($var) }
+            when List { return $var.map({self.render($_)}).join }
+        }
+    }
+
+    method render(%t --> Str) {
+        my Str $rendered;
+
+        # After mutating the rendered string the positions of those
+        # other variables that need to be substituted changes and so
+        # we need to recalculate it, that is stored in this var.
+        my int $delta = 0;
+
+        with (%!templates{%t{$!name-label}}) -> %t-compiled {
+            $rendered = %t-compiled<path>.slurp;
+
+            for @(%t-compiled<vars>) -> %v {
+                die "Variable {%v<name>} not defined." unless %t{%v<name>};
+
+                # Replace the template variable.
+                with self.parse(%t{%v<name>}) -> $append {
+                    $rendered.substr-rw(%v<start-delim>[0] + $delta, %v<length>) = $append;
+
+                    # From delta remove %v<length> and add the length
+                    # of string we just appended.
+                    $delta += - %v<length> + $append.chars;
+                }
+            }
+        } else {
+            die "Unrecognized template: {%t{$!name-label}}.";
+        }
+        return $rendered;
+    }
+}
diff --git a/t/00-basic.rakutest b/t/00-basic.rakutest
new file mode 100644
index 0000000..bcd096f
--- /dev/null
+++ b/t/00-basic.rakutest
@@ -0,0 +1,5 @@
+use Test;
+
+plan 1;
+
+use-ok 'Template::Nest::Fast';
-- 
cgit 1.4.1-2-gfad0