From 4e3450de4e8043dd9cdc2e309ae1aaac6392cb1b Mon Sep 17 00:00:00 2001
From: jaina heartles <me@heartles.xyz>
Date: Sat, 10 Dec 2022 00:02:04 -0800
Subject: [PATCH] Add equals operator to template engine

---
 src/template/lib.zig       | 57 ++++++++++++++++++++++++++++++++------
 src/template/test.tmp.html |  2 ++
 2 files changed, 50 insertions(+), 9 deletions(-)

diff --git a/src/template/lib.zig b/src/template/lib.zig
index 8fbcbe1..4c13fc8 100644
--- a/src/template/lib.zig
+++ b/src/template/lib.zig
@@ -15,6 +15,7 @@ pub fn main() !void {
             .bar = .{ .x = "x" },
             .qux = false,
             .quxx = true,
+            .quxx2 = true,
             .maybe_foo = @as(?[]const u8, "foo"),
             .maybe_bar = @as(?[]const u8, null),
             .x = "y",
@@ -168,6 +169,7 @@ fn EvaluateExpression(
         .arg_deref => |names| Deref(Args, names),
         .capture_deref => |names| Deref(Captures, names),
         .context_deref => |names| Deref(Context, names),
+        .equals => bool,
     };
 }
 
@@ -181,6 +183,16 @@ fn evaluateExpression(
         .arg_deref => |names| deref(args, names),
         .capture_deref => |names| deref(captures, names),
         .context_deref => |names| deref(context, names),
+        .equals => |eql| {
+            const lhs = evaluateExpression(eql.lhs, args, captures, context);
+            const rhs = evaluateExpression(eql.rhs, args, captures, context);
+            const T = @TypeOf(lhs, rhs);
+            if (comptime std.meta.trait.isZigString(T)) {
+                return std.mem.eql(u8, lhs, rhs);
+            } else if (comptime std.meta.trait.isContainer(T) and @hasDecl(T, "eql")) {
+                return T.eql(lhs, rhs);
+            } else return lhs == rhs;
+        },
     };
 }
 
@@ -400,29 +412,50 @@ fn parseExpression(comptime tokens: ControlTokenIter) ParseResult(ControlTokenIt
     comptime {
         var iter = tokens;
 
-        var expr: Expression = while (iter.next()) |token| switch (token) {
+        var last_valid_iter: ?ControlTokenIter = null;
+        var expr: ?Expression = null;
+        while (iter.next()) |token| switch (token) {
             .whitespace => {},
             .period => {
                 const names = parseDeref(iter);
                 iter = names.new_iter;
-                break .{ .arg_deref = names.item };
+                expr = .{ .arg_deref = names.item };
+                last_valid_iter = iter;
             },
             .dollar => {
                 const names = parseDeref(iter);
                 iter = names.new_iter;
-                break .{ .capture_deref = names.item };
+                expr = .{ .capture_deref = names.item };
+                last_valid_iter = iter;
             },
             .percent => {
                 const names = parseDeref(iter);
                 iter = names.new_iter;
-                break .{ .context_deref = names.item };
+                expr = .{ .context_deref = names.item };
+                last_valid_iter = iter;
             },
-            else => @compileError("TODO"),
+            .equals => {
+                const next = iter.next() orelse break;
+                if (next == .equals) {
+                    const lhs = expr orelse break;
+                    const rhs = parseExpression(iter);
+                    iter = rhs.new_iter;
+
+                    expr = .{
+                        .equals = &.{
+                            .lhs = lhs,
+                            .rhs = rhs.item,
+                        },
+                    };
+                    last_valid_iter = iter;
+                } else break;
+            },
+            else => break,
         };
 
         return .{
-            .new_iter = iter,
-            .item = expr,
+            .new_iter = last_valid_iter orelse @compileError("Invalid Expression"),
+            .item = expr orelse @compileError("Invalid Expression"),
         };
     }
 }
@@ -518,7 +551,7 @@ fn parseControlBlock(comptime tokens: ControlTokenIter) ParseResult(ControlToken
             },
             else => {
                 @compileLog(iter.row);
-                @compileError("TODO" ++ @tagName(token));
+                @compileError("TODO " ++ @tagName(token) ++ " " ++ token.text);
             },
         };
 
@@ -702,10 +735,16 @@ const TemplateItem = union(enum) {
     statement: Statement,
 };
 
+const EqualsExpr = struct {
+    lhs: Expression,
+    rhs: Expression,
+};
+
 const Expression = union(enum) {
     arg_deref: []const []const u8,
     capture_deref: []const []const u8,
     context_deref: []const []const u8,
+    equals: *const EqualsExpr,
 };
 
 const For = struct {
@@ -830,7 +869,7 @@ const ControlTokenIter = struct {
             },
             else => {
                 var idx: usize = 0;
-                while (idx < remaining.len and std.mem.indexOfScalar(u8, "{}.#|$/=@ \t\n\r", remaining[idx]) == null) : (idx += 1) {}
+                while (idx < remaining.len and std.mem.indexOfScalar(u8, "{}.#|$/=@,% \t\n\r", remaining[idx]) == null) : (idx += 1) {}
 
                 self.start += idx - 1;
                 return .{ .text = remaining[0..idx] };
diff --git a/src/template/test.tmp.html b/src/template/test.tmp.html
index 29930ed..2dc07ff 100644
--- a/src/template/test.tmp.html
+++ b/src/template/test.tmp.html
@@ -14,6 +14,8 @@
       {$b}:
       {= /for =}
       {= /for}
+      {#if .quxx == .quxx2}eql{#else}neq{/if}
+      {#if .quxx == .qux}eql{#else}neq{/if}
       {#if .qux=}
         qux
       {=#elif .quxx=}