// Copyright (C) 2023-2024  Lightpanda (Selecy SAS)
//
// Francis Bouvier <francis@lightpanda.io>
// Pierre Tachoire <pierre@lightpanda.io>
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <https://www.gnu.org/licenses/>.

const std = @import("std");
const Allocator = std.mem.Allocator;

const log = @import("../log.zig");
const parser = @import("../browser/netsurf.zig");

pub const Id = u32;

const Node = @This();

id: Id,
_node: *parser.Node,
set_child_nodes_event: bool,

// Whenever we send a node to the client, we register it here for future lookup.
// We maintain a node -> id and id -> node lookup.
pub const Registry = struct {
    node_id: u32,
    allocator: Allocator,
    arena: std.heap.ArenaAllocator,
    node_pool: std.heap.MemoryPool(Node),
    lookup_by_id: std.AutoHashMapUnmanaged(Id, *Node),
    lookup_by_node: std.HashMapUnmanaged(*parser.Node, *Node, NodeContext, std.hash_map.default_max_load_percentage),

    pub fn init(allocator: Allocator) Registry {
        return .{
            .node_id = 0,
            .lookup_by_id = .{},
            .lookup_by_node = .{},
            .allocator = allocator,
            .arena = std.heap.ArenaAllocator.init(allocator),
            .node_pool = std.heap.MemoryPool(Node).init(allocator),
        };
    }

    pub fn deinit(self: *Registry) void {
        const allocator = self.allocator;
        self.lookup_by_id.deinit(allocator);
        self.lookup_by_node.deinit(allocator);
        self.node_pool.deinit();
        self.arena.deinit();
    }

    pub fn reset(self: *Registry) void {
        self.lookup_by_id.clearRetainingCapacity();
        self.lookup_by_node.clearRetainingCapacity();
        _ = self.arena.reset(.{ .retain_with_limit = 1024 });
        _ = self.node_pool.reset(.{ .retain_with_limit = 1024 });
    }

    pub fn register(self: *Registry, n: *parser.Node) !*Node {
        const node_lookup_gop = try self.lookup_by_node.getOrPut(self.allocator, n);
        if (node_lookup_gop.found_existing) {
            return node_lookup_gop.value_ptr.*;
        }

        // on error, we're probably going to abort the entire browser context
        // but, just in case, let's try to keep things tidy.
        errdefer _ = self.lookup_by_node.remove(n);

        const node = try self.node_pool.create();
        errdefer self.node_pool.destroy(node);

        const id = self.node_id;
        self.node_id = id + 1;

        node.* = .{
            ._node = n,
            .id = id,
            .set_child_nodes_event = false,
        };

        node_lookup_gop.value_ptr.* = node;
        try self.lookup_by_id.putNoClobber(self.allocator, id, node);
        return node;
    }
};

const NodeContext = struct {
    pub fn hash(_: NodeContext, n: *parser.Node) u64 {
        return std.hash.Wyhash.hash(0, std.mem.asBytes(&@intFromPtr(n)));
    }

    pub fn eql(_: NodeContext, a: *parser.Node, b: *parser.Node) bool {
        return @intFromPtr(a) == @intFromPtr(b);
    }
};

// Searches are a 3 step process:
// 1 - Dom.performSearch
// 2 - Dom.getSearchResults
// 3 - Dom.discardSearchResults
//
// For a given browser context, we can have multiple active searches. I.e.
// performSearch could be called multiple times without getSearchResults or
// discardSearchResults being called. We keep these active searches in the
// browser context's node_search_list, which is a SearchList. Since we don't
// expect many active searches (mostly just 1), a list is fine to scan through.
pub const Search = struct {
    name: []const u8,
    node_ids: []const Id,

    pub const List = struct {
        registry: *Registry,
        search_id: u16 = 0,
        arena: std.heap.ArenaAllocator,
        searches: std.ArrayListUnmanaged(Search) = .{},

        pub fn init(allocator: Allocator, registry: *Registry) List {
            return .{
                .registry = registry,
                .arena = std.heap.ArenaAllocator.init(allocator),
            };
        }

        pub fn deinit(self: *List) void {
            self.arena.deinit();
        }

        pub fn reset(self: *List) void {
            self.search_id = 0;
            self.searches = .{};
            _ = self.arena.reset(.{ .retain_with_limit = 4096 });
        }

        pub fn create(self: *List, nodes: []const *parser.Node) !Search {
            const id = self.search_id;
            defer self.search_id = id +% 1;

            const arena = self.arena.allocator();

            const name = switch (id) {
                0 => "0",
                1 => "1",
                2 => "2",
                3 => "3",
                4 => "4",
                5 => "5",
                6 => "6",
                7 => "7",
                8 => "8",
                9 => "9",
                else => try std.fmt.allocPrint(arena, "{d}", .{id}),
            };

            var registry = self.registry;
            const node_ids = try arena.alloc(Id, nodes.len);
            for (nodes, node_ids) |node, *node_id| {
                node_id.* = (try registry.register(node)).id;
            }

            const search = Search{
                .name = name,
                .node_ids = node_ids,
            };
            try self.searches.append(arena, search);
            return search;
        }

        pub fn remove(self: *List, name: []const u8) void {
            for (self.searches.items, 0..) |search, i| {
                if (std.mem.eql(u8, name, search.name)) {
                    _ = self.searches.swapRemove(i);
                    return;
                }
            }
        }

        pub fn get(self: *const List, name: []const u8) ?Search {
            for (self.searches.items) |search| {
                if (std.mem.eql(u8, name, search.name)) {
                    return search;
                }
            }
            return null;
        }
    };
};

// Need a custom writer, because we can't just serialize the node as-is.
// Sometimes we want to serializ the node without chidren, sometimes with just
// its direct children, and sometimes the entire tree.
// (For now, we only support direct children)

pub const Writer = struct {
    opts: Opts,
    node: *const Node,
    registry: *Registry,

    pub const Opts = struct {};

    pub fn jsonStringify(self: *const Writer, w: anytype) !void {
        self.toJSON(w) catch |err| {
            // The only error our jsonStringify method can return is
            // @TypeOf(w).Error. In other words, our code can't return its own
            // error, we can only return a writer error. Kinda sucks.
            log.err(.cdp, "json stringify", .{ .err = err });
            return error.OutOfMemory;
        };
    }

    fn toJSON(self: *const Writer, w: anytype) !void {
        try w.beginObject();
        try self.writeCommon(self.node, false, w);

        {
            var registry = self.registry;
            const child_nodes = try parser.nodeGetChildNodes(self.node._node);
            const child_count = try parser.nodeListLength(child_nodes);

            var i: usize = 0;
            try w.objectField("children");
            try w.beginArray();
            for (0..child_count) |_| {
                const child = (try parser.nodeListItem(child_nodes, @intCast(i))) orelse break;
                const child_node = try registry.register(child);
                try w.beginObject();
                try self.writeCommon(child_node, true, w);
                try w.endObject();
                i += 1;
            }
            try w.endArray();

            try w.objectField("childNodeCount");
            try w.write(i);
        }

        try w.endObject();
    }

    fn writeCommon(self: *const Writer, node: *const Node, include_child_count: bool, w: anytype) !void {
        try w.objectField("nodeId");
        try w.write(node.id);

        try w.objectField("backendNodeId");
        try w.write(node.id);

        const n = node._node;

        if (try parser.nodeParentNode(n)) |p| {
            const parent_node = try self.registry.register(p);
            try w.objectField("parentId");
            try w.write(parent_node.id);
        }

        const _map = try parser.nodeGetAttributes(n);
        if (_map) |map| {
            const attr_count = try parser.namedNodeMapGetLength(map);
            try w.objectField("attributes");
            try w.beginArray();
            for (0..attr_count) |i| {
                const attr = try parser.namedNodeMapItem(map, @intCast(i)) orelse continue;
                try w.write(try parser.attributeGetName(attr));
                try w.write(try parser.attributeGetValue(attr) orelse continue);
            }
            try w.endArray();
        }

        try w.objectField("nodeType");
        try w.write(@intFromEnum(try parser.nodeType(n)));

        try w.objectField("nodeName");
        try w.write(try parser.nodeName(n));

        try w.objectField("localName");
        try w.write(try parser.nodeLocalName(n));

        try w.objectField("nodeValue");
        try w.write((try parser.nodeValue(n)) orelse "");

        if (include_child_count) {
            try w.objectField("childNodeCount");
            const child_nodes = try parser.nodeGetChildNodes(n);
            try w.write(try parser.nodeListLength(child_nodes));
        }

        try w.objectField("documentURL");
        try w.write(null);

        try w.objectField("baseURL");
        try w.write(null);

        try w.objectField("xmlVersion");
        try w.write("");

        try w.objectField("compatibilityMode");
        try w.write("NoQuirksMode");

        try w.objectField("isScrollable");
        try w.write(false);
    }
};

const testing = @import("testing.zig");
test "cdp Node: Registry register" {
    var registry = Registry.init(testing.allocator);
    defer registry.deinit();

    try testing.expectEqual(0, registry.lookup_by_id.count());
    try testing.expectEqual(0, registry.lookup_by_node.count());

    var doc = try testing.Document.init("<a id=a1>link1</a><div id=d2><p>other</p></div>");
    defer doc.deinit();

    {
        const n = (try doc.querySelector("#a1")).?;
        const node = try registry.register(n);
        const n1b = registry.lookup_by_id.get(0).?;
        const n1c = registry.lookup_by_node.get(node._node).?;
        try testing.expectEqual(node, n1b);
        try testing.expectEqual(node, n1c);

        try testing.expectEqual(0, node.id);
        try testing.expectEqual(n, node._node);
    }

    {
        const n = (try doc.querySelector("p")).?;
        const node = try registry.register(n);
        const n1b = registry.lookup_by_id.get(1).?;
        const n1c = registry.lookup_by_node.get(node._node).?;
        try testing.expectEqual(node, n1b);
        try testing.expectEqual(node, n1c);

        try testing.expectEqual(1, node.id);
        try testing.expectEqual(n, node._node);
    }
}

test "cdp Node: search list" {
    var registry = Registry.init(testing.allocator);
    defer registry.deinit();

    var search_list = Search.List.init(testing.allocator, &registry);
    defer search_list.deinit();

    {
        // empty search list, noops
        search_list.remove("0");
        try testing.expectEqual(null, search_list.get("0"));
    }

    {
        // empty nodes
        const s1 = try search_list.create(&.{});
        try testing.expectEqual("0", s1.name);
        try testing.expectEqual(0, s1.node_ids.len);

        const s2 = search_list.get("0").?;
        try testing.expectEqual("0", s2.name);
        try testing.expectEqual(0, s2.node_ids.len);

        search_list.remove("0");
        try testing.expectEqual(null, search_list.get("0"));
    }

    {
        var doc = try testing.Document.init("<a id=a1></a><a id=a2></a>");
        defer doc.deinit();

        const s1 = try search_list.create(try doc.querySelectorAll("a"));
        try testing.expectEqual("1", s1.name);
        try testing.expectEqualSlices(u32, &.{ 0, 1 }, s1.node_ids);

        try testing.expectEqual(2, registry.lookup_by_id.count());
        try testing.expectEqual(2, registry.lookup_by_node.count());

        const s2 = try search_list.create(try doc.querySelectorAll("#a1"));
        try testing.expectEqual("2", s2.name);
        try testing.expectEqualSlices(u32, &.{0}, s2.node_ids);

        const s3 = try search_list.create(try doc.querySelectorAll("#a2"));
        try testing.expectEqual("3", s3.name);
        try testing.expectEqualSlices(u32, &.{1}, s3.node_ids);

        try testing.expectEqual(2, registry.lookup_by_id.count());
        try testing.expectEqual(2, registry.lookup_by_node.count());
    }
}

test "cdp Node: Writer" {
    var registry = Registry.init(testing.allocator);
    defer registry.deinit();

    var doc = try testing.Document.init("<a id=a1></a><a id=a2></a>");
    defer doc.deinit();

    {
        const node = try registry.register(doc.asNode());
        const json = try std.json.stringifyAlloc(testing.allocator, Writer{
            .node = node,
            .opts = .{},
            .registry = &registry,
        }, .{});
        defer testing.allocator.free(json);

        try testing.expectJson(.{
            .nodeId = 0,
            .backendNodeId = 0,
            .nodeType = 9,
            .nodeName = "#document",
            .localName = "",
            .nodeValue = "",
            .documentURL = null,
            .baseURL = null,
            .xmlVersion = "",
            .isScrollable = false,
            .compatibilityMode = "NoQuirksMode",
            .childNodeCount = 1,
            .children = &.{.{
                .nodeId = 1,
                .backendNodeId = 1,
                .nodeType = 1,
                .nodeName = "HTML",
                .localName = "html",
                .nodeValue = "",
                .childNodeCount = 2,
                .documentURL = null,
                .baseURL = null,
                .xmlVersion = "",
                .compatibilityMode = "NoQuirksMode",
                .isScrollable = false,
            }},
        }, json);
    }

    {
        const node = registry.lookup_by_id.get(1).?;
        const json = try std.json.stringifyAlloc(testing.allocator, Writer{
            .node = node,
            .opts = .{},
            .registry = &registry,
        }, .{});
        defer testing.allocator.free(json);

        try testing.expectJson(.{
            .nodeId = 1,
            .backendNodeId = 1,
            .nodeType = 1,
            .nodeName = "HTML",
            .localName = "html",
            .nodeValue = "",
            .childNodeCount = 2,
            .documentURL = null,
            .baseURL = null,
            .xmlVersion = "",
            .compatibilityMode = "NoQuirksMode",
            .isScrollable = false,
            .children = &.{ .{
                .nodeId = 2,
                .backendNodeId = 2,
                .nodeType = 1,
                .nodeName = "HEAD",
                .localName = "head",
                .nodeValue = "",
                .childNodeCount = 0,
                .documentURL = null,
                .baseURL = null,
                .xmlVersion = "",
                .compatibilityMode = "NoQuirksMode",
                .isScrollable = false,
                .parentId = 1,
            }, .{
                .nodeId = 3,
                .backendNodeId = 3,
                .nodeType = 1,
                .nodeName = "BODY",
                .localName = "body",
                .nodeValue = "",
                .childNodeCount = 2,
                .documentURL = null,
                .baseURL = null,
                .xmlVersion = "",
                .compatibilityMode = "NoQuirksMode",
                .isScrollable = false,
                .parentId = 1,
            } },
        }, json);
    }
}