Implement multiple tag query

src/main.zig

@@ -45,7 +45,7 @@ pub fn main() !void {
     std.debug.print("\n\n", .{});
 
     const jsonQuery: [:0]const u8 =
-        \\{ "query" : "fur made_with:krita -fur:dusk", "limit" : 20 }
+        \\{ "query" : "fur made_with:krita date:2022", "limit" : 20 }
     ;
 
     var jquery = json.Obj.newFromString(jsonQuery);

src/request.zig

@@ -4,6 +4,7 @@ const Db = @import("Db.zig");
 const Item = @import("Item.zig");
 const Tag = @import("Tag.zig");
 const json = @import("json.zig");
+const util = @import("util.zig");
 
 pub fn process(jobj: *json.Obj, db: *Db) !void {
     var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
@@ -56,26 +57,34 @@ pub fn query(jobj: *json.Obj, db: *Db, allocator: std.mem.Allocator) !json.Obj {
     var jret = json.Obj.newArray();
 
     // Go through each tag
-    var iter = std.mem.split(u8, query_str, " ");
+    var tag_iter = std.mem.split(u8, query_str, " ");
-    const opt_tag = iter.next();
 
-    if (opt_tag) |tag| {
+    var ids = std.ArrayList([]u8).init(allocator);
+    defer {
+        for (ids.items) |item| {
+            Db.free(item.ptr);
+        }
+        ids.deinit();
+    }
+
+    while (tag_iter.next()) |tag| {
         // Get the tag selector: "tag:<tag>"
-        const tag_sel = try std.mem.concat(allocator, u8, &[_][]const u8{"tag:", tag});
+        const tag_sel = try std.mem.concat(allocator, u8, &[_][]const u8{ "tag:", tag });
         defer allocator.free(tag_sel);
 
         // Get the items that have that tag: "<item1> <item2> <item3>"
-        const tag_str = db.get(tag_sel) orelse return jret;
+        try ids.append(db.get(tag_sel) orelse return jret);
-        defer Db.free(tag_str.ptr);
 
-        // Iterate through the items id
+        // This has been deferred before.
-        var item_iter = std.mem.split(u8, tag_str, " ");
+        //defer Db.free(tag_str.ptr);
-        while (item_iter.next()) |item_id| {
+    }
+
+    var id_iter = util.intersection(ids.items);
+    while (id_iter.next()) |item_id| {
         const item = (try Item.getById(item_id, db, allocator)) orelse continue;
 
         jret.arrayAdd(&item.toJson());
     }
-    }
 
     return jret;
 }

src/util.zig

@@ -0,0 +1,42 @@
+const std = @import("std");
+
+
+pub const IntersectionIterator = struct {
+    ref: std.mem.TokenIterator(u8),
+    rest: []const []const u8,
+
+    /// Returns the next occurrence or null. Returned value is owned by originally passed slice
+    pub fn next(self: *IntersectionIterator) ?[]const u8{
+        // If this returns null, there's no more items to check. We're finished.
+        const needle = self.ref.next() orelse return null;
+
+        // Search into every one of the strings
+        haystack: for (self.rest) |haystack| {
+
+            // The items are separated by spaces, iterate through those
+            var haystack_iter = std.mem.tokenize(u8, haystack, " ");
+
+            // If the word is found, it short circuits and tries the next haystack
+            while (haystack_iter.next()) |hay_blade| {
+                if (std.mem.eql(u8, hay_blade, needle)) continue :haystack;
+            }
+
+            // If this point is reached, the needle wasn't found.
+            // Try the next one
+            return self.next();
+        }
+
+        // If we got here, no not-matching haysack was found. A match!
+        return needle;
+    }
+};
+
+/// Finds the common tokens inside space separated strings
+/// and returns a slice to the first token that matches
+pub fn intersection(slices: []const []const u8) IntersectionIterator {
+    // Tokenize the first entry and save the rest as references to check
+    return IntersectionIterator{
+        .ref = std.mem.tokenize(u8, slices[0], " "),
+        .rest = slices[1..],
+    };
+}