Refactor template code

src/template/lib.zig

@@ -15,15 +15,19 @@ pub fn main() !void {
 
 pub fn execute(writer: anytype, comptime template: []const u8, args: anytype) !void {
     @setEvalBranchQuota(@intCast(u32, template.len * 8));
-    const tmpl = comptime parseTemplate(ControlTokenIter{ .text = template }, .root);
+
+    const tokens = comptime parseTemplateTokens(ControlTokenIter{ .text = template });
+    const tmpl = comptime parseTemplate(tokens, 0, .root);
     try executeTemplate(writer, tmpl.item, args, .{});
 }
 
 fn executeTemplate(writer: anytype, comptime items: []const TemplateItem, args: anytype, captures: anytype) !void {
-    inline for (items) |it| switch (it) {
+    inline for (items) |it| {
-        .text => |text| try writer.writeAll(text),
+        switch (it) {
-        .statement => |stmt| try executeStatement(writer, stmt, args, captures),
+            .text => |text| try writer.writeAll(text),
-    };
+            .statement => |stmt| try executeStatement(writer, stmt, args, captures),
+        }
+    }
 }
 
 fn executeStatement(writer: anytype, comptime stmt: Statement, args: anytype, captures: anytype) !void {
@@ -32,24 +36,24 @@ fn executeStatement(writer: anytype, comptime stmt: Statement, args: anytype, ca
             const val = evaluateExpression(expr, args, captures);
             try print(writer, val);
         },
-        .for_loop => |loop| {
+        .@"for" => |loop| {
-            const iterable = evaluateExpression(loop.iterable, args, captures);
+            const iterable = evaluateExpression(loop.header.iterable, args, captures);
             const subtemplate = loop.subtemplate;
             for (iterable) |v| {
                 try executeTemplate(
                     writer,
                     subtemplate,
                     args,
-                    addCapture(captures, loop.capture, v),
+                    addCapture(captures, loop.header.capture, v),
                 );
             }
         },
-        .if_statement => |if_stmt| {
+        .@"if" => |if_stmt| {
-            const condition = evaluateExpression(if_stmt.condition, args, captures);
+            const condition = evaluateExpression(if_stmt.header.condition, args, captures);
             const subtemplate = if_stmt.subtemplate;
             if (condition) try executeTemplate(writer, subtemplate, args, captures);
         },
-        else => @compileError("TODO"),
+        //else => @compileError("TODO"),
     }
 }
 
@@ -123,60 +127,129 @@ const TemplateType = enum {
     if_block,
 };
 
-fn parseTemplate(comptime tokens: ControlTokenIter, comptime template_type: TemplateType) ParseResult(ControlTokenIter, []const TemplateItem) {
+fn parseTemplate(
+    comptime tokens: []const TemplateToken,
+    comptime start: usize,
+    comptime template_type: TemplateType,
+) ParseResult(usize, []const TemplateItem) {
     comptime {
-        var iter = tokens;
+        var i: usize = start;
-        var items: []const TemplateItem = &.{};
         var current_text: []const u8 = "";
+        var items: []const TemplateItem = &.{};
 
-        parse_loop: while (iter.next()) |token| {
+        while (i < tokens.len) : (i += 1) {
-            switch (token) {
+            switch (tokens[i]) {
-                .whitespace, .text => |text| current_text = current_text ++ text,
+                .text => |text| current_text = current_text ++ text,
-                .open_bracket => {
+                .whitespace => |wsp| {
-                    const next = iter.peek() orelse @compileError("Unexpected end of template");
+                    if (i != tokens.len - 1 and tokens[i + 1] == .control_block)
-                    if (next == .open_bracket) {
+                        if (tokens[i + 1].control_block.strip_before)
-                        current_text = current_text ++ "{";
+                            continue;
-                        _ = iter.next();
+                    current_text = current_text ++ wsp;
-                    } else {
+                },
-                        if (current_text.len != 0) {
+                .control_block => |cb| {
-                            items = items ++ [_]TemplateItem{.{ .text = current_text }};
+                    if (current_text.len != 0) {
-                            current_text = "";
+                        items = items ++ [_]TemplateItem{.{ .text = current_text }};
+                        current_text = "";
+                    }
+
+                    switch (cb.block) {
+                        .expression => |expr| items = items ++ [_]TemplateItem{.{ .statement = .{ .expression = expr } }},
+                        .if_header => |header| {
+                            const subtemplate = parseTemplate(tokens, i + 1, .if_block);
+                            items = items ++ [_]TemplateItem{.{
+                                .statement = .{
+                                    .@"if" = .{
+                                        .subtemplate = subtemplate.item,
+                                        .header = header,
+                                    },
+                                },
+                            }};
+                            i = subtemplate.new_iter;
+                        },
+                        .for_header => |header| {
+                            const subtemplate = parseTemplate(tokens, i + 1, .for_block);
+                            items = items ++ [_]TemplateItem{.{
+                                .statement = .{
+                                    .@"for" = .{
+                                        .subtemplate = subtemplate.item,
+                                        .header = header,
+                                    },
+                                },
+                            }};
+                            i = subtemplate.new_iter;
+                        },
+                        .end_for => if (template_type == .for_block)
+                            break
+                        else
+                            @compileError("Unexpected /for tag"),
+                        .end_if => if (template_type == .if_block)
+                            break
+                        else
+                            @compileError("Unexpected /if tag"),
+                    }
+
+                    if (i != tokens.len - 1 and tokens[i] == .control_block) {
+                        if (tokens[i].control_block.strip_after and tokens[i + 1] == .whitespace) {
+                            i += 1;
                         }
-                        const result = parseControlBlock(iter);
-                        iter = result.new_iter;
-                        const stmt = result.item.statement;
-                        if (stmt == .end_for) {
-                            if (template_type == .for_block) break :parse_loop else @compileError("Unexpected end statement");
-                        } else if (stmt == .end_if) {
-                            if (template_type == .if_block) break :parse_loop else @compileError("Unexpected end statement");
-                        }
-                        items = items ++ [_]TemplateItem{.{ .statement = stmt }};
                     }
                 },
-                .close_bracket => {
-                    const next = iter.next() orelse @compileError("Unexpected end of template");
-                    if (next == .close_bracket) current_text = current_text ++ "}" else @compileError("Unpaired close bracket, did you mean \"}}\"?");
-                },
-                .period => current_text = current_text ++ ".",
-                .pound => current_text = current_text ++ "#",
-                .pipe => current_text = current_text ++ "|",
-                .dollar => current_text = current_text ++ "$",
-                .slash => current_text = current_text ++ "/",
-                .equals => current_text = current_text ++ "=",
             }
-        }
+        } else if (template_type != .root) @compileError("End tag not found");
 
-        if (current_text.len != 0) {
+        if (current_text.len != 0) items = items ++ [_]TemplateItem{.{ .text = current_text }};
-            items = items ++ [_]TemplateItem{.{ .text = current_text }};
-        }
 
         return .{
-            .new_iter = iter,
+            .new_iter = i,
             .item = items,
         };
     }
 }
 
+const TemplateToken = union(enum) {
+    text: []const u8,
+    whitespace: []const u8,
+    control_block: ControlBlock,
+};
+
+fn parseTemplateTokens(comptime tokens: ControlTokenIter) []const TemplateToken {
+    comptime {
+        var iter = tokens;
+        var items: []const TemplateToken = &.{};
+
+        while (iter.next()) |token| switch (token) {
+            .whitespace => |wsp| items = items ++ [_]TemplateToken{.{ .whitespace = wsp }},
+            .text => |text| items = items ++ [_]TemplateToken{.{ .text = text }},
+            .open_bracket => {
+                const next = iter.next() orelse @compileError("Unexpected end of template");
+                if (next == .open_bracket) {
+                    items = items ++ [_]TemplateToken{.{ .text = "{" }};
+                } else {
+                    iter.putBack(next);
+                    const result = parseControlBlock(iter);
+                    iter = result.new_iter;
+                    items = items ++ [_]TemplateToken{.{ .control_block = result.item }};
+                }
+            },
+            .close_bracket => {
+                const next = iter.next() orelse @compileError("Unexpected end of template");
+                if (next == .close_bracket)
+                    items = items ++ [_]TemplateToken{.{ .text = "}" }}
+                else
+                    @compileError("Unpaired close bracket, did you mean \"}}\"?");
+            },
+            .period => items = items ++ [_]TemplateToken{.{ .text = "." }},
+            .pound => items = items ++ [_]TemplateToken{.{ .text = "#" }},
+            .pipe => items = items ++ [_]TemplateToken{.{ .text = "|" }},
+            .dollar => items = items ++ [_]TemplateToken{.{ .text = "$" }},
+            .slash => items = items ++ [_]TemplateToken{.{ .text = "/" }},
+            .equals => items = items ++ [_]TemplateToken{.{ .text = "=" }},
+        };
+
+        return items;
+    }
+}
+
 fn parseExpression(comptime tokens: ControlTokenIter) ParseResult(ControlTokenIter, Expression) {
     comptime {
         var iter = tokens;
@@ -206,70 +279,58 @@ fn parseExpression(comptime tokens: ControlTokenIter) ParseResult(ControlTokenIt
 fn parseControlBlock(comptime tokens: ControlTokenIter) ParseResult(ControlTokenIter, ControlBlock) {
     comptime {
         var iter = tokens;
-        var first_token: bool = true;
-        var strip_before: bool = false;
-        var stmt: Statement = while (iter.next()) |token| {
-            defer first_token = false;
-            switch (token) {
-                .equals => {
-                    if (first_token) {
-                        strip_before = true;
-                    } else @compileError("Unexpected '='");
-                },
-                .whitespace => {},
-                .pound => {
-                    const next = iter.next() orelse @compileError("Unexpected end of template");
-                    if (next != .text) @compileError("Expected keyword following '#' character");
-                    const text = next.text;
-                    const keyword = std.meta.stringToEnum(Keyword, text) orelse @compileError("Unknown keyword: " ++ text);
 
-                    switch (keyword) {
+        const strip_before = if (iter.next()) |first| blk: {
-                        .@"for" => {
+            if (first == .equals) {
-                            const result = parseForLoop(iter);
+                break :blk true;
-                            // statemnt already finished so just return
-                            return .{
-                                .new_iter = result.new_iter,
-                                .item = .{
-                                    .statement = .{ .for_loop = result.item },
-                                    .strip_before = false,
-                                    .strip_after = false,
-                                },
-                            };
-                        },
-                        .@"if" => {
-                            const result = parseIfStatement(iter);
-                            return .{
-                                .new_iter = result.new_iter,
-                                .item = .{
-                                    .statement = .{ .if_statement = result.item },
-                                    .strip_before = false,
-                                    .strip_after = false,
-                                },
-                            };
-                        },
-
-                        //else => @compileError("TODO"),
-                    }
-                },
-                .slash => {
-                    const next = iter.next() orelse @compileError("Unexpected end of template");
-                    if (next != .text) @compileError("Expected keyword following '/' character");
-                    const text = next.text;
-                    const keyword = std.meta.stringToEnum(EndKeyword, text) orelse @compileError("Unknown keyword: " ++ text);
-
-                    switch (keyword) {
-                        .@"for" => break .{ .end_for = {} },
-                        .@"if" => break .{ .end_if = {} },
-                    }
-                },
-                .period, .dollar => {
-                    iter.putBack(token);
-                    const expr = parseExpression(iter);
-                    iter = expr.new_iter;
-                    break .{ .expression = expr.item };
-                },
-                else => @compileError("TODO"),
             }
+
+            iter.putBack(first);
+            break :blk false;
+        } else @compileError("Unexpected end of template");
+
+        var stmt: ControlBlock.Data = while (iter.next()) |token| switch (token) {
+            .equals => @compileError("Unexpected '='"),
+            .whitespace => {},
+            .pound => {
+                const next = iter.next() orelse @compileError("Unexpected end of template");
+                if (next != .text) @compileError("Expected keyword following '#' character");
+                const text = next.text;
+                const keyword = std.meta.stringToEnum(Keyword, text) orelse @compileError("Unknown keyword: " ++ text);
+
+                switch (keyword) {
+                    .@"for" => {
+                        const result = parseForHeader(iter);
+                        iter = result.new_iter;
+                        break .{ .for_header = result.item };
+                    },
+                    .@"if" => {
+                        const result = parseIfHeader(iter);
+                        iter = result.new_iter;
+                        break .{ .if_header = result.item };
+                    },
+
+                    //else => @compileError("TODO"),
+                }
+            },
+            .slash => {
+                const next = iter.next() orelse @compileError("Unexpected end of template");
+                if (next != .text) @compileError("Expected keyword following '/' character");
+                const text = next.text;
+                const keyword = std.meta.stringToEnum(EndKeyword, text) orelse @compileError("Unknown keyword: " ++ text);
+
+                switch (keyword) {
+                    .@"for" => break .{ .end_for = {} },
+                    .@"if" => break .{ .end_if = {} },
+                }
+            },
+            .period, .dollar => {
+                iter.putBack(token);
+                const expr = parseExpression(iter);
+                iter = expr.new_iter;
+                break .{ .expression = expr.item };
+            },
+            else => @compileError("TODO"),
         };
 
         // search for end of statement
@@ -288,7 +349,7 @@ fn parseControlBlock(comptime tokens: ControlTokenIter) ParseResult(ControlToken
             .close_bracket => return .{
                 .new_iter = iter,
                 .item = .{
-                    .statement = stmt,
+                    .block = stmt,
                     .strip_before = strip_before,
                     .strip_after = strip_after,
                 },
@@ -325,7 +386,7 @@ fn endControlBlock(comptime tokens: ControlTokenIter) ControlTokenIter {
     }
 }
 
-fn parseForLoop(comptime tokens: ControlTokenIter) ParseResult(ControlTokenIter, ForLoop) {
+fn parseForHeader(comptime tokens: ControlTokenIter) ParseResult(ControlTokenIter, ForHeader) {
     comptime {
         const iterable = parseExpression(tokens);
         var iter = iterable.new_iter;
@@ -348,26 +409,28 @@ fn parseForLoop(comptime tokens: ControlTokenIter) ParseResult(ControlTokenIter,
             const token = iter.next() orelse @compileError("Unexpected end of template");
             if (token != .pipe) @compileError("Unexpected token");
         }
-        iter = endControlBlock(iter);
 
-        const subtemplate = parseTemplate(iter, .for_block);
+        return .{
-
+            .new_iter = iter,
-        return .{ .new_iter = subtemplate.new_iter, .item = .{
+            .item = .{
-            .iterable = iterable.item,
+                .iterable = iterable.item,
-            .subtemplate = subtemplate.item,
+                .capture = capture,
-            .capture = capture,
+            },
-        } };
+        };
     }
 }
 
-fn parseIfStatement(comptime tokens: ControlTokenIter) ParseResult(ControlTokenIter, IfStatement) {
+fn parseIfHeader(comptime tokens: ControlTokenIter) ParseResult(ControlTokenIter, IfHeader) {
     comptime {
         const condition = parseExpression(tokens);
-        var iter = endControlBlock(condition.new_iter);
+        var iter = condition.new_iter;
 
-        const subtemplate = parseTemplate(iter, .if_block);
+        return .{
-
+            .new_iter = iter,
-        return .{ .new_iter = subtemplate.new_iter, .item = .{ .condition = condition.item, .subtemplate = subtemplate.item } };
+            .item = .{
+                .condition = condition.item,
+            },
+        };
     }
 }
 
@@ -415,27 +478,40 @@ const Expression = union(enum) {
     capture_deref: []const []const u8,
 };
 
-const ForLoop = struct {
+const For = struct {
     subtemplate: []const TemplateItem,
+    header: ForHeader,
+};
+
+const ForHeader = struct {
     iterable: Expression,
     capture: []const u8,
 };
 
-const IfStatement = struct {
+const If = struct {
     subtemplate: []const TemplateItem,
+    header: IfHeader,
+};
+
+const IfHeader = struct {
     condition: Expression,
 };
 
 const Statement = union(enum) {
     expression: Expression,
-    for_loop: ForLoop,
+    @"for": For,
-    end_for: void,
+    @"if": If,
-    if_statement: IfStatement,
-    end_if: void,
 };
 
 const ControlBlock = struct {
-    statement: Statement,
+    const Data = union(enum) {
+        expression: Expression,
+        for_header: ForHeader,
+        end_for: void,
+        if_header: IfHeader,
+        end_if: void,
+    };
+    block: Data,
     strip_before: bool,
     strip_after: bool,
 };

src/template/test.tmp.html

@@ -9,8 +9,11 @@
     <h2> {{ REAL BRACKETS }} </h2>
 
     <section>
-      {= #for .baz |$f|}{#for $f |$b|}{$b}:{/for}
+      {= #for .baz |$f| =}
-      {/for}
+      {= #for $f |$b| =}
+      {$b}:
+      {= /for =}
+      {= /for =}
       {#if .qux}qux!{/if}
       {#if .quxx}quxx!{/if}
     </section>