package service

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"net/url"
	"os"
	"time"
)

type KetoService interface {
	CheckPermission(ctx context.Context, subject, namespace, object, relation string) (bool, error)
	CreateRelation(ctx context.Context, namespace, object, relation, subject string) error
	DeleteRelation(ctx context.Context, namespace, object, relation, subject string) error
}

type ketoService struct {
	readURL  string
	writeURL string
	client   *http.Client
}

func NewKetoService() KetoService {
	readURL := os.Getenv("KETO_READ_URL")
	if readURL == "" {
		readURL = "http://keto:4466"
	}
	writeURL := os.Getenv("KETO_WRITE_URL")
	if writeURL == "" {
		writeURL = "http://keto:4467"
	}

	return &ketoService{
		readURL:  readURL,
		writeURL: writeURL,
		client:   &http.Client{},
	}
}

type checkResponse struct {
	Allowed bool `json:"allowed"`
}

func (s *ketoService) CheckPermission(ctx context.Context, subject, namespace, object, relation string) (bool, error) {
	u, _ := url.Parse(fmt.Sprintf("%s/relation-tuples/check", s.readURL))
	q := u.Query()
	q.Set("namespace", namespace)
	q.Set("object", object)
	q.Set("relation", relation)
	q.Set("subject_id", subject)
	u.RawQuery = q.Encode()

	req, _ := http.NewRequestWithContext(ctx, "GET", u.String(), nil)
	resp, err := s.client.Do(req)
	if err != nil {
		return false, err
	}
	defer resp.Body.Close()

	if resp.StatusCode == http.StatusForbidden {
		return false, nil
	}
	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return false, fmt.Errorf("keto returned status %d: %s", resp.StatusCode, string(body))
	}

	var res checkResponse
	if err := json.NewDecoder(resp.Body).Decode(&res); err != nil {
		return false, err
	}

	return res.Allowed, nil
}

func (s *ketoService) CreateRelation(ctx context.Context, namespace, object, relation, subject string) error {
	u := fmt.Sprintf("%s/admin/relation-tuples", s.writeURL)
	payload := map[string]interface{}{
		"namespace":  namespace,
		"object":     object,
		"relation":   relation,
		"subject_id": subject,
	}
	body, _ := json.Marshal(payload)

	// Exponential Backoff Retry Logic
	var lastErr error
	maxRetries := 3
	backoff := 100 * time.Millisecond

	for i := 0; i < maxRetries; i++ {
		req, _ := http.NewRequestWithContext(ctx, "PUT", u, bytes.NewReader(body))
		req.Header.Set("Content-Type", "application/json")

		resp, err := s.client.Do(req)
		if err == nil {
			defer resp.Body.Close()
			if resp.StatusCode == http.StatusCreated || resp.StatusCode == http.StatusNoContent || resp.StatusCode == http.StatusOK {
				slog.Info("Keto relation created", "namespace", namespace, "object", object, "relation", relation, "subject", subject)
				return nil
			}
			resBody, _ := io.ReadAll(resp.Body)
			lastErr = fmt.Errorf("keto returned status %d: %s", resp.StatusCode, string(resBody))
		} else {
			lastErr = err
		}

		time.Sleep(backoff)
		backoff *= 2
	}

	slog.Error("Keto create relation failed after retries", "error", lastErr)
	return lastErr
}

func (s *ketoService) DeleteRelation(ctx context.Context, namespace, object, relation, subject string) error {
	u, _ := url.Parse(fmt.Sprintf("%s/relation-tuples", s.writeURL))
	q := u.Query()
	q.Set("namespace", namespace)
	q.Set("object", object)
	q.Set("relation", relation)
	q.Set("subject_id", subject)
	u.RawQuery = q.Encode()

	req, _ := http.NewRequestWithContext(ctx, "DELETE", u.String(), nil)
	resp, err := s.client.Do(req)
	if err != nil {
		return err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusNoContent && resp.StatusCode != http.StatusOK {
		resBody, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("keto returned status %d: %s", resp.StatusCode, string(resBody))
	}

	slog.Info("Keto relation deleted", "namespace", namespace, "object", object, "relation", relation, "subject", subject)
	return nil
}