const std = @import("std");
const Allocator = std.mem.Allocator;
const Location = @import("resolver.zig").Location;
const Ip2location = @import("Ip2location.zig");
const Cache = Ip2location.Cache;

const Self = @This();

const log = std.log.scoped(.ipwhois);

allocator: Allocator,
/// Zig 0.16 requires an explicit `Io` for filesystem and HTTP work.
io: std.Io,
http_client: std.http.Client,
cache: *Cache,

pub fn init(allocator: Allocator, io: std.Io, cache_path: []const u8) !Self {
    const cache = try allocator.create(Cache);
    errdefer allocator.destroy(cache);
    cache.* = try .init(allocator, io, cache_path);
    return .{
        .allocator = allocator,
        .io = io,
        .http_client = std.http.Client{ .allocator = allocator, .io = io },
        .cache = cache,
    };
}

pub fn deinit(self: *Self) void {
    self.cache.deinit();
    self.allocator.destroy(self.cache);
    self.http_client.deinit();
}

pub fn lookup(self: *Self, ip_str: []const u8) ?Location {
    // Parse IP to u128 for cache lookup
    const parsed = Ip2location.packIp(ip_str) orelse return null;
    const ip_u128 = parsed.key;
    const family = parsed.family;

    // Check cache first
    if (self.cache.get(ip_u128)) |result|
        return result;

    // Fetch from API
    const result = self.fetch(ip_str) catch |err| {
        log.err("API lookup failed: {}", .{err});
        return null;
    };

    // Store in cache
    self.cache.put(ip_u128, family, result) catch |err| {
        log.warn("Failed to cache result: {}", .{err});
    };

    return result;
}

fn fetch(self: *Self, ip_str: []const u8) !Location {
    log.info("Fetching geolocation for IP {s}", .{ip_str});

    if (@import("builtin").is_test) return error.LookupUnavailableInUnitTest;

    var buf: [256]u8 = undefined;
    var w = std.Io.Writer.fixed(&buf);
    try w.writeAll("https://ipwho.is/");
    try w.writeAll(ip_str);
    // Request only the fields we need. `country_code` drives unit selection,
    // which cannot be derived from `country` without matching display text.
    try w.writeAll("?fields=city,region,country,country_code,latitude,longitude&output=json");

    var response_buf: [4096]u8 = undefined;
    var writer = std.Io.Writer.fixed(&response_buf);
    const result = try self.http_client.fetch(.{
        .location = .{ .url = w.buffered() },
        .method = .GET,
        .response_writer = &writer,
        .extra_headers = &.{
            .{ .name = "User-Agent", .value = "wttr.in" },
        },
    });

    if (result.status != .ok) {
        log.err("API returned status {}", .{result.status});
        return error.ApiError;
    }

    const response_body = response_buf[0..writer.end];

    // Parse JSON response
    const parsed = try std.json.parseFromSlice(
        std.json.Value,
        self.allocator,
        response_body,
        .{},
    );
    defer parsed.deinit();

    const obj = parsed.value.object;

    // Check for success field
    if (obj.get("success")) |success| {
        if (success == .bool and !success.bool) {
            const msg = if (obj.get("message")) |m| if (m == .string) m.string else "unknown" else "unknown";
            log.err("API returned error for ip {s}: {s}", .{ ip_str, msg });
            return error.ApiError;
        }
    }

    const lat = obj.get("latitude") orelse return error.MissingLatitude;
    const lon = obj.get("longitude") orelse return error.MissingLongitude;
    if (lat != .float and lat != .integer) {
        log.err("Latitude returned from ipwho.is for ip {s} is not a number", .{ip_str});
        return error.MissingLatitude;
    }
    if (lon != .float and lon != .integer) {
        log.err("Longitude returned from ipwho.is for ip {s} is not a number", .{ip_str});
        return error.MissingLongitude;
    }

    const city = getString(obj, "city");
    const region = getString(obj, "region");
    const country = getString(obj, "country");

    const display_name = Location.buildDisplayName(
        self.allocator,
        city,
        region,
        country,
        ip_str,
    );

    const lat_val: f64 = if (lat == .float) @floatCast(lat.float) else @floatFromInt(lat.integer);
    const lon_val: f64 = if (lon == .float) @floatCast(lon.float) else @floatFromInt(lon.integer);

    return Location{
        .allocator = self.allocator,
        .name = display_name,
        .coords = .{
            .latitude = lat_val,
            .longitude = lon_val,
        },
        .iso_country = Location.isoFrom(getString(obj, "country_code")),
    };
}

inline fn getString(obj: std.json.ObjectMap, key: []const u8) []const u8 {
    const maybe_val = obj.get(key);
    if (maybe_val == null) return "";
    if (maybe_val.? != .string) return "";
    return maybe_val.?.string;
}