implement array index filter

1 files changed, 31 insertions, 6 deletions

diff --git a/src/jq/execute.zig b/src/jq/execute.zig
index 9857d46..dfad6c4 100644
--- a/src/jq/execute.zig
+++ b/src/jq/execute.zig
@@ -4,19 +4,44 @@ const Instr = @import("./compile.zig").Instr;
 
 pub const ExecuteError = error{
     Unimplemented,
+    InvalidType,
+    InternalError,
 };
 
 pub fn execute(allocator: std.mem.Allocator, instrs: []const Instr, input: jv.Value) !jv.Value {
-    _ = allocator;
+    var value_stack = try std.array_list.Aligned(jv.Value, null).initCapacity(allocator, 16);
+    defer value_stack.deinit(allocator);
+
+    try value_stack.append(allocator, input);
+
     const len = instrs.len;
     var pc: usize = 0;
     while (pc < len) {
         const cur = instrs[pc];
-        _ = switch (cur.op) {
-            .nop => void,
-            .identity => return input,
-        };
+        switch (cur) {
+            .nop => {},
+            .array_index => {
+                const v1 = value_stack.pop() orelse return error.InternalError;
+                const v1_integer = switch (v1) {
+                    .integer => |integer| integer,
+                    else => return error.InvalidType,
+                };
+                const v2 = value_stack.pop() orelse return error.InternalError;
+                const v2_array = switch (v2) {
+                    .array => |array| array,
+                    else => return error.InvalidType,
+                };
+                const index: usize = @intCast(v1_integer);
+                const result = if (index < v2_array.items.len) v2_array.items[index] else .null;
+                try value_stack.append(allocator, result);
+            },
+            .literal => |value| {
+                try value_stack.append(allocator, value.*);
+            },
+        }
         pc += 1;
     }
-    return ExecuteError.Unimplemented;
+
+    const result = value_stack.pop() orelse return error.InternalError;
+    return result;
 }