const std = @import("std");
const httpz = @import("httpz");
const WeatherProvider = @import("../weather/Provider.zig");
const Resolver = @import("../location/resolver.zig").Resolver;
const QueryParams = @import("query.zig").QueryParams;
const formatted = @import("../render/formatted.zig");
const line = @import("../render/line.zig");
const json = @import("../render/json.zig");
const v2 = @import("../render/v2.zig");
const custom = @import("../render/custom.zig");
const help = @import("help.zig");

pub const HandleWeatherOptions = struct {
    provider: WeatherProvider,
    resolver: *Resolver,
    geoip: *@import("../location/GeoIp.zig"),
};

pub fn handleWeather(
    opts: *HandleWeatherOptions,
    req: *httpz.Request,
    res: *httpz.Response,
) !void {
    // Get location from path parameter or query string
    const location = req.param("location") orelse blk: {
        // Check query string for location parameter
        const query_string = req.url.query;
        const params = try QueryParams.parse(req.arena, query_string);
        defer {
            if (params.format) |f| req.arena.free(f);
            if (params.lang) |l| req.arena.free(l);
        }

        if (params.location) |loc| {
            break :blk loc;
        } else {
            // Fall back to IP-based detection
            const client_ip = getClientIP(req);
            break :blk client_ip;
        }
    };

    // Handle special endpoints
    if (location[0] == ':') {
        if (std.mem.eql(u8, location, ":help")) {
            res.content_type = .TEXT;
            res.body = help.help_page;
            return;
        } else if (std.mem.eql(u8, location, ":translation")) {
            res.content_type = .TEXT;
            res.body = help.translation_page;
            return;
        }
    }

    try handleWeatherInternal(opts, req, res, location);
}

fn getClientIP(req: *httpz.Request) []const u8 {
    // Check X-Forwarded-For header first (for proxies)
    if (req.header("x-forwarded-for")) |xff| {
        return parseXForwardedFor(xff);
    }

    // Check X-Real-IP header
    if (req.header("x-real-ip")) |real_ip| {
        return real_ip;
    }

    // Fall back to empty (no IP available)
    return "";
}

fn parseXForwardedFor(xff: []const u8) []const u8 {
    // Take first IP from comma-separated list
    var iter = std.mem.splitScalar(u8, xff, ',');
    if (iter.next()) |first_ip| {
        return std.mem.trim(u8, first_ip, " \t");
    }
    return "";
}

fn handleWeatherInternal(
    opts: *HandleWeatherOptions,
    req: *httpz.Request,
    res: *httpz.Response,
    location_query: []const u8,
) !void {
    const req_alloc = req.arena;

    // Resolve location. By the time we get here, we really
    // should have a location from the path, query string, or
    // client IP lookup. So if we have an empty location parameter, it
    // is better to 404 than to fake it with a London response
    if (location_query.len == 0) {
        res.status = 404;
        res.body = "Location not found\n";
        return;
    }
    const location = opts.resolver.resolve(location_query) catch |err| {
        switch (err) {
            error.LocationNotFound => {
                res.status = 404;
                res.body = "Location not found\n";
                return;
            },
            else => {
                res.status = 500;
                res.body = "Internal server error\n";
                return;
            },
        }
    };

    // Fetch weather using coordinates
    const weather = opts.provider.fetch(req_alloc, location.coords) catch |err| {
        switch (err) {
            error.LocationNotFound => {
                res.status = 404;
                res.body = "Location not found\n";
                return;
            },
            else => {
                res.status = 500;
                res.body = "Internal server error\n";
                return;
            },
        }
    };
    defer weather.deinit();

    const query_string = req.url.query;
    const params = try QueryParams.parse(req_alloc, query_string);
    defer {
        if (params.format) |f| req_alloc.free(f);
        if (params.lang) |l| req_alloc.free(l);
    }

    // Determine if imperial units should be used
    // Priority: explicit ?u or ?m > lang=us > US IP > default metric
    const use_imperial = blk: {
        if (params.units) |u| {
            break :blk u == .uscs;
        }
        if (params.lang) |lang| {
            if (std.mem.eql(u8, lang, "us")) {
                break :blk true;
            }
        }
        const client_ip = getClientIP(req);
        if (client_ip.len > 0) {
            if (opts.geoip.isUSIP(client_ip)) {
                break :blk true;
            }
        }
        break :blk false;
    };

    const output = if (params.format) |fmt| blk: {
        if (std.mem.eql(u8, fmt, "j1")) {
            res.content_type = .JSON;
            break :blk try json.render(req_alloc, weather);
        } else if (std.mem.eql(u8, fmt, "v2")) {
            break :blk try v2.render(req_alloc, weather, use_imperial);
        } else if (std.mem.startsWith(u8, fmt, "%")) {
            break :blk try custom.render(req_alloc, weather, fmt, use_imperial);
        } else {
            break :blk try line.render(req_alloc, weather, fmt, use_imperial);
        }
    } else try formatted.render(req_alloc, weather, .{ .use_imperial = use_imperial });

    // Add coordinates header using response allocator
    const coords_header = try std.fmt.allocPrint(res.arena, "{d:.4},{d:.4}", .{ location.coords.latitude, location.coords.longitude });
    res.headers.add("X-Location-Coordinates", coords_header);

    if (res.content_type != .JSON)
        res.content_type = .TEXT;

    res.body = output;
}

test "parseXForwardedFor extracts first IP" {
    try std.testing.expectEqualStrings("192.168.1.1", parseXForwardedFor("192.168.1.1"));
    try std.testing.expectEqualStrings("10.0.0.1", parseXForwardedFor("10.0.0.1, 172.16.0.1"));
    try std.testing.expectEqualStrings("203.0.113.1", parseXForwardedFor("203.0.113.1, 198.51.100.1, 192.0.2.1"));
}

test "parseXForwardedFor trims whitespace" {
    try std.testing.expectEqualStrings("192.168.1.1", parseXForwardedFor(" 192.168.1.1 "));
    try std.testing.expectEqualStrings("10.0.0.1", parseXForwardedFor("  10.0.0.1  , 172.16.0.1"));
}

test "parseXForwardedFor handles empty string" {
    try std.testing.expectEqualStrings("", parseXForwardedFor(""));
}

test "imperial units selection logic" {
    // This test documents the priority order for unit selection:
    // 1. Explicit ?u or ?m parameter (highest priority)
    // 2. lang=us parameter
    // 3. US IP detection
    // 4. Default to metric

    // The actual logic is tested through integration tests
    // This test just verifies the QueryParams parsing works
    const allocator = std.testing.allocator;

    const params_u = try QueryParams.parse(allocator, "u");
    try std.testing.expectEqual(QueryParams.Units.uscs, params_u.units.?);

    const params_m = try QueryParams.parse(allocator, "m");
    try std.testing.expectEqual(QueryParams.Units.metric, params_m.units.?);

    const params_lang = try QueryParams.parse(allocator, "lang=us");
    defer allocator.free(params_lang.lang.?);
    try std.testing.expectEqualStrings("us", params_lang.lang.?);
}