5 files changed, 152 insertions, 0 deletions
diff --git a/src/z/js/parser/builtin.zig b/src/z/js/parser/builtin.zig
new file mode 100644
index 0000000..fc96fc3
--- /dev/null
+++ b/src/z/js/parser/builtin.zig
@@ -0,0 +1,17 @@
+const std = @import("std");
+
+const parser = @import("root.zig");
+const Parser = parser.Parser;
+const Result = parser.Result;
+
+pub fn literal(lit: []const u8) Parser(void) {
+    return .fromType(struct {
+        pub fn parse(buffer: []const u8) !Result(void) {
+            if (std.mem.startsWith(u8, buffer, lit)) {
+                return .{ void{}, buffer[lit.len..] };
+            }
+
+            return error.Literal;
+        }
+    });
+}
diff --git a/src/z/js/parser/lexical_grammar.zig b/src/z/js/parser/lexical_grammar.zig
new file mode 100644
index 0000000..7060766
--- /dev/null
+++ b/src/z/js/parser/lexical_grammar.zig
@@ -0,0 +1,3 @@
+const parser = @import("root.zig");
+const Result = parser.Result;
+
diff --git a/src/z/js/parser/parser.zig b/src/z/js/parser/parser.zig
new file mode 100644
index 0000000..b73d895
--- /dev/null
+++ b/src/z/js/parser/parser.zig
@@ -0,0 +1,117 @@
+const std = @import("std");
+
+const mod = @import("root.zig");
+const Result = mod.Result;
+
+pub fn Parser(T: type) type {
+    const R = Result(T);
+
+    return struct {
+        parse: *const fn ([]const u8) anyerror!R,
+
+        pub fn parseAll(self: *const @This(), buffer: []const u8) !T {
+            const value, const next = try self.parse(buffer);
+
+            if (next.len > 0) {
+                return error.NotExhaustive;
+            }
+
+            return value;
+        }
+
+        pub fn fromType(P: type) @This() {
+            return .{ .parse = P.parse };
+        }
+
+        pub fn variants(V: type) @This() {
+            if (@typeInfo(T) != .@"union") {
+                @compileError("variants is only allowed with an union as result type");
+            }
+
+            return .{
+                .parse = struct {
+                    fn parse(buffer: []const u8) !R {
+                        inline for (std.meta.fields(T)) |field| {
+                            if (@field(V, field.name).parse(buffer)) |result| {
+                                const value, const next = result;
+                                return .{
+                                    @unionInit(T, field.name, value),
+                                    next,
+                                };
+                            } else |_| { }
+                        }
+
+                        return error.Variants;
+                    }
+                }.parse,
+            };
+        }
+
+        pub fn any(P: type, comptime parsers: []const struct { Parser(P), T }) @This() {
+            return .{
+                .parse = struct {
+                    fn parse(buffer: []const u8) !R {
+                        inline for (parsers) |pair| {
+                            const parser, const value = pair;
+
+                            if (parser.parse(buffer)) |result| {
+                                _, const next = result;
+                                return .{ value, next };
+                            } else |_| { }
+                        }
+                        return error.Any;
+                    }
+                }.parse,
+            };
+        }
+    };
+}
+
+test "variants" {
+    const Char = union(enum) {
+        upper: u8,
+        lower: u8,
+        space: void,
+    };
+
+    const parser: Parser(Char) = .variants(struct {
+        const upper: Parser(u8) = .any(void, &.{
+            .{ mod.builtin.literal("A"), 'A' },
+            .{ mod.builtin.literal("B"), 'B' },
+        });
+
+        const lower: Parser(u8) = .any(void, &.{
+            .{ mod.builtin.literal("a"), 'a' },
+            .{ mod.builtin.literal("b"), 'b' },
+        });
+
+        const space: Parser(void) = mod.builtin.literal(" ");
+    });
+
+    {
+        const result = try parser.parseAll("a");
+        try std.testing.expect(result.lower == 'a');
+    }
+
+    {
+        const result = try parser.parseAll("b");
+        try std.testing.expect(result.lower == 'b');
+    }
+
+    {
+        const result = try parser.parseAll("A");
+        try std.testing.expect(result.upper == 'A');
+    }
+
+    {
+        const result = try parser.parseAll("B");
+        try std.testing.expect(result.upper == 'B');
+    }
+
+    {
+        const result = try parser.parseAll(" ");
+        try std.testing.expect(result == .space);
+    }
+
+    try std.testing.expect(parser.parseAll("c") == error.Variants);
+}
diff --git a/src/z/js/parser/result.zig b/src/z/js/parser/result.zig
new file mode 100644
index 0000000..5cc5878
--- /dev/null
+++ b/src/z/js/parser/result.zig
@@ -0,0 +1,4 @@
+
+pub fn Result(T: type) type {
+    return struct { T, []const u8 };
+}
diff --git a/src/z/js/parser/root.zig b/src/z/js/parser/root.zig
new file mode 100644
index 0000000..a6be9ca
--- /dev/null
+++ b/src/z/js/parser/root.zig
@@ -0,0 +1,11 @@
+const std = @import("std");
+
+pub const lexical_grammar = @import("lexical_grammar.zig");
+
+pub const Result = @import("result.zig").Result;
+pub const Parser = @import("parser.zig").Parser;
+pub const builtin = @import("builtin.zig");
+
+test {
+    _ = std.testing.refAllDecls(@This());
+}