const std = @import("std");
const http = @import("apple_pie");
const hzzp = @import("hzzp");

const images_dir_path = "./images";

pub fn main() anyerror!void {
    std.log.info("welcome to webscale", .{});

    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
    defer _ = gpa.deinit();

    // TODO: configurable addr via env var
    const bind_addr = try std.net.Address.parseIp("0.0.0.0", 8080);
    std.log.info("serving on {}", .{bind_addr});

    // TODO: configurable path via env var
    try std.fs.cwd().makePath(images_dir_path);

    try http.listenAndServe(
        &gpa.allocator,
        bind_addr,
        comptime http.router.router(&[_]http.router.Route{
            http.router.get("/", index),
            http.router.post("/api/upload", uploadFile),
            http.router.get("/i/:filename", fetchFile),
        }),
    );
}

fn index(response: *http.Response, request: http.Request) !void {
    try response.writer().writeAll("Hello Zig!");
}

fn generateImageId(buffer: []u8) []const u8 {
    var i: usize = 0;

    const seed = @truncate(u64, @bitCast(u128, std.time.nanoTimestamp()));
    var r = std.rand.DefaultPrng.init(seed);

    while (i < 16) : (i += 1) {
        // random ascii lowercase char
        var idx = @intCast(u8, r.random.uintLessThan(u5, 24));
        var letter = @as(u8, 97) + idx;
        buffer[i] = letter;
    }

    return buffer[0..i];
}

const StreamT = std.io.FixedBufferStream([]const u8);

const ContentDisposition = struct {
    name: []const u8,
    filename: []const u8,
};

const Part = struct {
    disposition: ContentDisposition,
    content_type: []const u8,
};

const Multipart = struct {
    stream: StreamT,
    boundary: []const u8,
    cursor: usize = 0,

    const Self = @This();

    // TODO: move boundary_buffer to allocator
    pub fn init(body: []const u8, content_type: []const u8, boundary_buffer: []u8) !Multipart {
        // parse content_type into what we want (the boundary)
        var it = std.mem.split(content_type, ";");
        const should_be_multipart = it.next() orelse return error.MissingContentType;
        std.log.debug("should be multipart: {s}", .{should_be_multipart});
        if (!std.mem.eql(u8, should_be_multipart, "multipart/form-data"))
            return error.InvalidContentType;

        const should_be_boundary = it.next() orelse return error.MissingBoundary;
        std.log.debug("should be boundary: {s} {d}", .{ should_be_boundary, should_be_boundary.len });
        if (!std.mem.startsWith(u8, should_be_boundary, " boundary="))
            return error.InvalidBoundary;

        var boundary_it = std.mem.split(should_be_boundary, "=");
        _ = boundary_it.next();
        const boundary_value = boundary_it.next() orelse return error.InvalidBoundary;
        std.log.debug("boundary value: {s} {d}", .{ boundary_value, boundary_value.len });

        const actual_boundary_value = try std.fmt.bufPrint(boundary_buffer, "--{s}", .{boundary_value});
        std.log.debug("actual boundary value: {s} {d}", .{ actual_boundary_value, actual_boundary_value.len });

        return Self{
            .stream = StreamT{ .buffer = body, .pos = 0 },
            .boundary = actual_boundary_value,
        };
    }

    pub fn next(self: *Self, hzzp_buffer: []u8) !?Part {
        var reader = self.stream.reader();
        // first self.boundary.len+2 bytes MUST be boundary + \r + \n
        var boundary_buffer: [512]u8 = undefined;
        const maybe_boundary_raw = (try reader.readUntilDelimiterOrEof(&boundary_buffer, '\r')).?;

        const maybe_boundary_strip1 = std.mem.trimRight(u8, maybe_boundary_raw, "\n");
        const maybe_boundary_strip2 = std.mem.trimRight(u8, maybe_boundary_strip1, "\r");
        if (!std.mem.eql(u8, maybe_boundary_strip2, self.boundary)) {
            std.log.err("expected '{s}', got '{s}'", .{ self.boundary, maybe_boundary_strip2 });
            return error.InvalidBoundaryBody;
        }

        // from there ownwards, its just http!
        var parser = hzzp.parser.request.create(hzzp_buffer, reader);

        // This is a hack so that it doesnt try to parse an http header.
        parser.state = .header;

        var content_disposition: ?ContentDisposition = null;
        var content_type: ?[]const u8 = null;

        while (try parser.next()) |event| {
            switch (event) {
                .status => unreachable,
                .header => |header| {
                    // TODO lowercase header name
                    if (std.mem.eql(u8, header.name, "Content-Disposition")) {
                        // parse disposition
                        var disposition_it = std.mem.split(header.value, ";");
                        _ = disposition_it.next();

                        var dispo_name: []const u8 = undefined;
                        var dispo_filename: []const u8 = undefined;

                        while (disposition_it.next()) |disposition_part_raw| {
                            const disposition_part = std.mem.trim(u8, disposition_part_raw, " ");
                        }

                        content_disposition = ContentDisposition{
                            .name = dispo_name,
                            .filename = dispo_filename,
                        };
                    } else if (std.mem.eql(u8, header.name, "Content-Type")) {
                        content_type = header.value;
                    }
                },
                .end => break,
                else => @panic("shit"),
            }
        }

        return Part{
            .disposition = content_disposition.?,
            .content_type = content_type.?,
        };
    }
};

fn uploadFile(response: *http.Response, request: http.Request) !void {
    std.log.info("upload! got {d} bytes", .{request.body.len});

    // find content-type header
    var it = request.iterator();
    var content_type: ?[]const u8 = null;
    while (it.next()) |header| {
        if (std.mem.eql(u8, header.key, "Content-Type")) {
            content_type = header.value;
        }
    }

    if (content_type == null) return error.InvalidContentType;

    // parse multipart data
    var multipart = try Multipart.init(request.body, content_type.?);
    var hzzp_buffer: [1024]u8 = undefined;

    while (try multipart.next(&hzzp_buffer)) |part| {
        std.log.info("part: {}", .{part});
    }

    var image_id_buffer: [256]u8 = undefined;
    const image_id = generateImageId(&image_id_buffer);

    var image_path_buffer: [512]u8 = undefined;
    const image_path = try std.fmt.bufPrint(
        &image_path_buffer,
        "{s}/{s}.jpg",
        .{ images_dir_path, image_id },
    );

    const image_file = try std.fs.cwd().createFile(image_path, .{});
    try image_file.writer().writeAll(request.body);

    try response.writer().writeAll(image_path);
}

fn fetchFile(response: *http.Response, request: http.Request, filename: []const u8) !void {
    std.log.info("got name: {s}", .{filename});
    var image_path_buffer: [512]u8 = undefined;

    const images_dir = try std.fs.cwd().openDir(images_dir_path, .{});
    const image_path = try std.fmt.bufPrint(
        &image_path_buffer,
        "{s}/{s}",
        .{ images_dir_path, filename },
    );

    // TODO return 404 on error
    const image_file = try std.fs.cwd().openFile(image_path, .{ .read = false });
    while (true) {
        var file_write_buffer: [1024]u8 = undefined;
        const bytes_read = try image_file.read(&file_write_buffer);
        if (bytes_read == 0) return;
        try response.writer().writeAll(&file_write_buffer);
    }
}