From 22a5d1617e79f176ecfca22d6c72be215f0da8b6 Mon Sep 17 00:00:00 2001
From: nsfisis <nsfisis@gmail.com>
Date: Sat, 17 Jan 2026 18:40:47 +0900
Subject: implement object key access

---
 src/jq/compile.zig |  3 +++
 src/jq/execute.zig | 13 +++++++++++++
 src/jq/parse.zig   | 15 +++++++++++++++
 src/root.zig       | 12 ++++++++++++
 4 files changed, 43 insertions(+)

(limited to 'src')

diff --git a/src/jq/compile.zig b/src/jq/compile.zig
index ddb4be5..0c30a3d 100644
--- a/src/jq/compile.zig
+++ b/src/jq/compile.zig
@@ -5,12 +5,14 @@ const Ast = @import("./parse.zig").Ast;
 pub const Opcode = enum {
     nop,
     array_index,
+    object_key,
     literal,
 };
 
 pub const Instr = union(Opcode) {
     nop,
     array_index,
+    object_key: []const u8,
     literal: *jv.Value,
 
     pub fn op(self: @This()) Opcode {
@@ -29,6 +31,7 @@ pub fn compile(allocator: std.mem.Allocator, compile_allocator: std.mem.Allocato
             try instrs.appendSlice(allocator, index_instrs);
             try instrs.append(allocator, .array_index);
         },
+        .object_key => |key| try instrs.append(allocator, .{ .object_key = key }),
         .literal => |value| try instrs.append(allocator, .{ .literal = value }),
     }
 
diff --git a/src/jq/execute.zig b/src/jq/execute.zig
index a07204a..8e9bbb0 100644
--- a/src/jq/execute.zig
+++ b/src/jq/execute.zig
@@ -66,6 +66,14 @@ const ValueStack = struct {
             else => error.InvalidType,
         };
     }
+
+    pub fn popObject(self: *Self) ExecuteError!jv.Object {
+        const value = try self.pop();
+        return switch (value) {
+            .object => |o| o,
+            else => error.InvalidType,
+        };
+    }
 };
 
 pub fn execute(allocator: std.mem.Allocator, instrs: []const Instr, input: jv.Value) !jv.Value {
@@ -86,6 +94,11 @@ pub fn execute(allocator: std.mem.Allocator, instrs: []const Instr, input: jv.Va
                 const result = if (index < array.items.len) array.items[index] else .null;
                 try value_stack.push(result);
             },
+            .object_key => |key| {
+                const obj = try value_stack.popObject();
+                const result = obj.get(key) orelse .null;
+                try value_stack.push(result);
+            },
             .literal => |value| {
                 try value_stack.push(value.*);
             },
diff --git a/src/jq/parse.zig b/src/jq/parse.zig
index 5269ef5..dc9f6b9 100644
--- a/src/jq/parse.zig
+++ b/src/jq/parse.zig
@@ -10,12 +10,14 @@ pub const ParseError = error{
 pub const AstKind = enum {
     identity,
     array_index,
+    object_key,
     literal,
 };
 
 pub const Ast = union(AstKind) {
     identity,
     array_index: *Ast,
+    object_key: []const u8,
     literal: *jv.Value,
 
     pub fn kind(self: @This()) AstKind {
@@ -42,6 +44,19 @@ pub fn parse(allocator: std.mem.Allocator, tokens: []const Token) !*Ast {
         return root;
     }
 
+    if (t2.kind() == .identifier) {
+        i += 1;
+        const t3 = tokens[i];
+        if (t3.kind() != .end) {
+            return error.InvalidQuery;
+        }
+        const root = try allocator.create(Ast);
+        root.* = .{
+            .object_key = t2.identifier,
+        };
+        return root;
+    }
+
     if (t2.kind() != .bracket_left) {
         return error.InvalidQuery;
     }
diff --git a/src/root.zig b/src/root.zig
index fa48c7b..f75f062 100644
--- a/src/root.zig
+++ b/src/root.zig
@@ -58,3 +58,15 @@ test "array index filter" {
         \\ 81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100]
     , ".[100]");
 }
+
+test "object key filter" {
+    var debug_allocator = std.heap.DebugAllocator(.{}).init;
+    defer std.debug.assert(debug_allocator.deinit() == .ok);
+    const allocator = debug_allocator.allocator();
+
+    try testRun("123", allocator, "{\"a\":123}", ".a");
+    try testRun("null", allocator, "{\"a\":123}", ".b");
+    try testRun("\"hello\"", allocator, "{\"foo\":\"hello\"}", ".foo");
+    try testRun("[1,2,3]", allocator, "{\"arr\":[1,2,3]}", ".arr");
+    try testRun("{\"bar\":true}", allocator, "{\"foo\":{\"bar\":true}}", ".foo");
+}
-- 
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