From 1225049f76568edb76e2abd98a8149d31b7bfaa8 Mon Sep 17 00:00:00 2001
From: Fernando Araoz <fernando@araozu.dev>
Date: Sat, 14 Dec 2024 06:24:13 -0500
Subject: [PATCH] feat: minimal parsing of statements

---
 CHANGELOG.md                |  6 ++--
 build.zig                   |  1 +
 src/02_syntax/statement.zig | 56 +++++++++++++++++++++++++++++++++++++
 src/02_syntax/variable.zig  | 10 +++----
 4 files changed, 64 insertions(+), 9 deletions(-)
 create mode 100644 src/02_syntax/statement.zig

diff --git a/CHANGELOG.md b/CHANGELOG.md
index e3e6abf..b9983b2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -31,8 +31,8 @@ Now in Zig!
 - [x] Lex single line comments
 - [x] Lex strings
 - [x] Lex grouping signs
-- [ ]
-
-
+- [x] Parse minimal expression
+- [x] Parse minimal variable binding
+- [x] Parse minimal statement
 
 
diff --git a/build.zig b/build.zig
index 1205135..32db097 100644
--- a/build.zig
+++ b/build.zig
@@ -94,6 +94,7 @@ pub fn build(b: *std.Build) void {
         "src/02_syntax/root.zig",
         "src/02_syntax/variable.zig",
         "src/02_syntax/expression.zig",
+        "src/02_syntax/statement.zig",
     };
     for (files) |file| {
         const file_unit_test = b.addTest(.{
diff --git a/src/02_syntax/statement.zig b/src/02_syntax/statement.zig
new file mode 100644
index 0000000..ecb5a3a
--- /dev/null
+++ b/src/02_syntax/statement.zig
@@ -0,0 +1,56 @@
+const std = @import("std");
+const lexic = @import("lexic");
+const expression = @import("expression.zig");
+const types = @import("./types.zig");
+const utils = @import("./utils.zig");
+const variable = @import("./variable.zig");
+
+const TokenStream = types.TokenStream;
+const ParseError = types.ParseError;
+
+pub const Statement = union(enum) {
+    VariableBinding: *variable.VariableBinding,
+
+    fn init(target: *Statement, tokens: *const TokenStream, pos: usize, allocator: std.mem.Allocator) ParseError!void {
+        // try to parse a variable definition
+
+        var vardef: variable.VariableBinding = undefined;
+        var parse_failed = false;
+        vardef.init(tokens, pos, allocator) catch |err| switch (err) {
+            error.Unmatched => {
+                parse_failed = true;
+            },
+            else => {
+                return err;
+            },
+        };
+        if (!parse_failed) {
+            // return the parsed variable definition
+            target.* = .{
+                .VariableBinding = &vardef,
+            };
+            return;
+        }
+
+        // fail
+        return ParseError.Unmatched;
+    }
+
+    fn deinit(self: @This()) void {
+        switch (self) {
+            .VariableBinding => |v| v.deinit(),
+        }
+    }
+};
+
+test "should parse a variable declaration statement" {
+    const input = "var my_variable = 322";
+    const tokens = try lexic.tokenize(input, std.testing.allocator);
+    defer tokens.deinit();
+
+    var statement: Statement = undefined;
+    try statement.init(&tokens, 0, std.testing.allocator);
+    defer statement.deinit();
+
+    // try std.testing.expectEqual(true, statement.is_mutable);
+}
diff --git a/src/02_syntax/variable.zig b/src/02_syntax/variable.zig
index 74f2bca..e4d9cbf 100644
--- a/src/02_syntax/variable.zig
+++ b/src/02_syntax/variable.zig
@@ -7,7 +7,7 @@ const utils = @import("./utils.zig");
 const TokenStream = types.TokenStream;
 const ParseError = types.ParseError;
 
-const VariableBinding = struct {
+pub const VariableBinding = struct {
     is_mutable: bool,
     datatype: ?*lexic.Token,
     identifier: *lexic.Token,
@@ -15,7 +15,7 @@ const VariableBinding = struct {
     alloc: std.mem.Allocator,
 
     /// Parses a variable binding
-    fn init(target: *VariableBinding, tokens: *const TokenStream, pos: usize, allocator: std.mem.Allocator) ParseError!void {
+    pub fn init(target: *VariableBinding, tokens: *const TokenStream, pos: usize, allocator: std.mem.Allocator) ParseError!void {
         std.debug.assert(pos < tokens.items.len);
 
         // try to parse a var keyword
@@ -42,9 +42,7 @@ const VariableBinding = struct {
 
         // parse expression
         if (pos + 3 >= tokens.items.len) return ParseError.Error;
-        var exp = allocator.create(expression.Expression) catch {
-            return ParseError.Error;
-        };
+        var exp = try allocator.create(expression.Expression);
         errdefer allocator.destroy(exp);
         exp.init(tokens, pos + 3) catch {
             return ParseError.Error;
@@ -60,7 +58,7 @@ const VariableBinding = struct {
         };
     }
 
-    fn deinit(self: *VariableBinding) void {
+    pub fn deinit(self: *VariableBinding) void {
         self.alloc.destroy(self.expression);
     }
 };