package goatcounter

import (
	"bytes"
	"context"
	"encoding/json"
	"io"
	"net/http"
	"time"

	"gitlab.com/tozd/go/errors"
	"go.alanpearce.eu/homestead/internal/config"
	"go.alanpearce.eu/x/log"
)

const timeout = 5 * time.Second

type Options struct {
	URL    *config.URL
	Logger *log.Logger
	Token  string
}

type URLs struct {
	count string
}

type Goatcounter struct {
	log    *log.Logger
	token  string
	client *http.Client
	urls   URLs
}

type hit struct {
	IP        string `json:"ip"`
	Path      string `json:"path"`
	Query     string `json:"query"`
	Referrer  string `json:"ref"`
	UserAgent string `json:"user_agent"`
}

type countBody struct {
	NoSessions bool  `json:"no_sessions"`
	Hits       []hit `json:"hits"`
}

func New(options *Options) *Goatcounter {
	baseURL := options.URL
	baseURL.Path = "/api/v0/"

	return &Goatcounter{
		log:   options.Logger,
		token: options.Token,
		client: &http.Client{
			Timeout: 5 * time.Second,
		},
		urls: URLs{
			count: baseURL.JoinPath("count").String(),
		},
	}
}

func (gc *Goatcounter) Count(r *http.Request) {
	err := gc.count(r)
	if err != nil {
		gc.log.Warn("could not log page view", "error", err)
	}
}

func (gc *Goatcounter) count(userReq *http.Request) error {
	body, err := json.Marshal(&countBody{
		NoSessions: true,
		Hits: []hit{
			{
				IP:        userReq.RemoteAddr,
				Path:      userReq.URL.Path,
				Query:     userReq.URL.RawQuery,
				Referrer:  userReq.Header.Get("Referer"),
				UserAgent: userReq.Header.Get("User-Agent"),
			},
		},
	})
	if err != nil {
		return errors.WithMessage(err, "could not marshal JSON")
	}

	ctx, cancel := context.WithTimeout(context.Background(), timeout)
	defer cancel()
	req, err := http.NewRequestWithContext(
		ctx,
		http.MethodPost,
		gc.urls.count,
		bytes.NewBuffer(body),
	)
	if err != nil {
		return errors.WithMessage(err, "could not create HTTP request")
	}
	req.Header.Set("Accept", "application/json")
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", "Bearer "+gc.token)

	go func(req *http.Request) {
		var body []byte

		res, err := gc.client.Do(req)
		if err != nil {
			gc.log.Warn("could not perform HTTP request", "error", err)
		}
		if res.Body != nil {
			defer res.Body.Close()

			body, err = io.ReadAll(res.Body)
			if err != nil {
				gc.log.Warn("could not read error body", "error", err)
			}
		}
		if res.StatusCode != http.StatusAccepted {
			gc.log.Warn("failed to log pageview", "status", res.StatusCode, "body", body)
		}
	}(req)

	return nil
}