feat: add popLeft and popRight to collections

src/collections.zig

@@ -634,3 +634,160 @@ pub const List = struct {
         return error.TooManyConflicts;
     }
 
+    pub fn popLeft(db: *Db, allocator: Allocator, name: []const u8) !?[]u8 {
+        const mk = try metaKey(allocator, name);
+        defer allocator.free(mk);
+
+        var attempt: usize = 0;
+        while (attempt < maxConflictRetries) : (attempt += 1) {
+            var txn = Transaction.begin(db);
+            defer txn.deinit();
+
+            var meta = try readMeta(&txn, allocator, mk);
+            if (meta.tail - meta.head <= 1) return null;
+            const seq = meta.head + 1;
+            meta.head += 1;
+
+            const ek = try elementKey(allocator, name, seq);
+            defer allocator.free(ek);
+            const value = try txn.get(allocator, ek) orelse return error.Malformed;
+            errdefer allocator.free(value);
+            try txn.delete(ek);
+            try writeMeta(&txn, mk, meta);
+
+            txn.commit() catch |err| {
+                allocator.free(value);
+                if (err == error.Conflict) continue;
+                return err;
+            };
+            return value;
+        }
+        return error.TooManyConflicts;
+    }
+
+    pub fn popRight(db: *Db, allocator: Allocator, name: []const u8) !?[]u8 {
+        const mk = try metaKey(allocator, name);
+        defer allocator.free(mk);
+
+        var attempt: usize = 0;
+        while (attempt < maxConflictRetries) : (attempt += 1) {
+            var txn = Transaction.begin(db);
+            defer txn.deinit();
+
+            var meta = try readMeta(&txn, allocator, mk);
+            if (meta.tail - meta.head <= 1) return null;
+            const seq = meta.tail - 1;
+            meta.tail -= 1;
+
+            const ek = try elementKey(allocator, name, seq);
+            defer allocator.free(ek);
+            const value = try txn.get(allocator, ek) orelse return error.Malformed;
+            errdefer allocator.free(value);
+            try txn.delete(ek);
+            try writeMeta(&txn, mk, meta);
+
+            txn.commit() catch |err| {
+                allocator.free(value);
+                if (err == error.Conflict) continue;
+                return err;
+            };
+            return value;
+        }
+        return error.TooManyConflicts;
+    }
+
+    pub fn len(db: *Db, allocator: Allocator, name: []const u8) !usize {
+        const mk = try metaKey(allocator, name);
+        defer allocator.free(mk);
+        const raw = try db.get(allocator, mk) orelse return 0;
+        defer allocator.free(raw);
+        if (raw.len != 16) return error.Malformed;
+        const head = std.mem.readInt(i64, raw[0..8], .big);
+        const tail = std.mem.readInt(i64, raw[8..16], .big);
+        return @intCast(tail - head - 1);
+    }
+
+    /// Redis-style inclusive range with negative indices counting from the
+    /// end (-1 is the last element). Out-of-range indices are clamped;
+    /// start > stop after clamping yields an empty result. Caller owns the
+    /// returned slice and each element.
+    pub fn range(db: *Db, allocator: Allocator, name: []const u8, start: i64, stop: i64) ![][]u8 {
+        const total: i64 = @intCast(try len(db, allocator, name));
+
+        var results = std.ArrayList([]u8).init(allocator);
+        errdefer {
+            for (results.items) |m| allocator.free(m);
+            results.deinit();
+        }
+        if (total == 0) return results.toOwnedSlice();
+
+        var lo = if (start < 0) total + start else start;
+        var hi = if (stop < 0) total + stop else stop;
+        if (lo < 0) lo = 0;
+        if (hi > total - 1) hi = total - 1;
+        if (lo > hi) return results.toOwnedSlice();
+
+        const p = try elementPrefix(allocator, name);
+        defer allocator.free(p);
+        var it = try db.scanPrefix(allocator, p);
+        defer it.deinit();
+
+        var idx: i64 = 0;
+        while (try it.next()) |entry| {
+            if (idx >= lo and idx <= hi) {
+                try results.append(try allocator.dupe(u8, entry.value));
+            }
+            idx += 1;
+        }
+        return results.toOwnedSlice();
+    }
+};
+
+// ---------------------------------------------------------------------
+// ZSet (sorted set: member -> score, plus a score-ordered index for
+// range/rank queries)
+// ---------------------------------------------------------------------
+
+pub const ZMember = struct {
+    member: []u8,
+    score: f64,
+
+    pub fn free(self: ZMember, allocator: Allocator) void {
+        allocator.free(self.member);
+    }
+};
+
+pub const ZSet = struct {
+    fn memberKey(allocator: Allocator, name: []const u8, member: []const u8) ![]u8 {
+        var out = std.ArrayList(u8).init(allocator);
+        errdefer out.deinit();
+        try out.append(nsTag);
+        try appendSegment(&out, "Z");
+        try appendSegment(&out, name);
+        try appendSegment(&out, "M");
+        try out.appendSlice(member);
+        return out.toOwnedSlice();
+    }
+
+    fn scorePrefix(allocator: Allocator, name: []const u8) ![]u8 {
+        var out = std.ArrayList(u8).init(allocator);
+        errdefer out.deinit();
+        try out.append(nsTag);
+        try appendSegment(&out, "Z");
+        try appendSegment(&out, name);
+        try appendSegment(&out, "S");
+        return out.toOwnedSlice();
+    }
+
+    fn scoreEntryKey(allocator: Allocator, name: []const u8, scoreVal: f64, member: []const u8) ![]u8 {
+        var out = std.ArrayList(u8).init(allocator);
+        errdefer out.deinit();
+        try out.append(nsTag);
+        try appendSegment(&out, "Z");
+        try appendSegment(&out, name);
+        try appendSegment(&out, "S");
+        try row.appendOrdered(&out, .{ .float = scoreVal });
+        try row.appendOrdered(&out, .{ .text = member });
+        return out.toOwnedSlice();
+    }
+