package client

import (
	"context"
	"encoding/json"
	"flag"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"time"

	"github.com/go-kit/log/level"
	"github.com/grafana/dskit/crypto/tls"

	"github.com/grafana/loki/v3/pkg/compactor/deletion"
	"github.com/grafana/loki/v3/pkg/util/log"
)

const (
	orgHeaderKey    = "X-Scope-OrgID"
	getDeletePath   = "/loki/api/v1/delete"
	cacheGenNumPath = "/loki/api/v1/cache/generation_numbers"
)

type HTTPConfig struct {
	TLSEnabled bool             `yaml:"tls_enabled"`
	TLS        tls.ClientConfig `yaml:",inline"`
}

// RegisterFlags adds the flags required to config this to the given FlagSet.
func (cfg *HTTPConfig) RegisterFlags(f *flag.FlagSet) {
	prefix := "compactor.client"
	f.BoolVar(&cfg.TLSEnabled, prefix+".tls-enabled", false,
		"Enable TLS in the HTTP client. This flag needs to be enabled when any other TLS flag is set. If set to false, insecure connection to HTTP server will be used.")
	cfg.TLS.RegisterFlagsWithPrefix(prefix, f)
}

type compactorHTTPClient struct {
	httpClient *http.Client

	deleteRequestsURL string
	cacheGenURL       string
}

// NewHTTPClient creates a client which talks to compactor over HTTP.
// It uses provided TLS config which creating HTTP client.
func NewHTTPClient(addr string, cfg HTTPConfig) (deletion.CompactorClient, error) {
	u, err := url.Parse(addr)
	if err != nil {
		level.Error(log.Logger).Log("msg", "error parsing url", "err", err)
		return nil, err
	}
	u.Path = getDeletePath
	deleteRequestsURL := u.String()

	u.Path = cacheGenNumPath
	cacheGenURL := u.String()

	transport := http.DefaultTransport.(*http.Transport).Clone()
	transport.MaxIdleConns = 250
	transport.MaxIdleConnsPerHost = 250

	if cfg.TLSEnabled {
		tlsCfg, err := cfg.TLS.GetTLSConfig()
		if err != nil {
			return nil, err
		}

		transport.TLSClientConfig = tlsCfg
	}

	return &compactorHTTPClient{
		httpClient:        &http.Client{Timeout: 5 * time.Second, Transport: transport},
		deleteRequestsURL: deleteRequestsURL,
		cacheGenURL:       cacheGenURL,
	}, nil
}

func (c *compactorHTTPClient) Name() string {
	return "http_client"
}

func (c *compactorHTTPClient) Stop() {}

func (c *compactorHTTPClient) GetAllDeleteRequestsForUser(ctx context.Context, userID string) ([]deletion.DeleteRequest, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, c.deleteRequestsURL, nil)
	if err != nil {
		level.Error(log.Logger).Log("msg", "error getting delete requests from the store", "err", err)
		return nil, err
	}

	req.Header.Set(orgHeaderKey, userID)

	resp, err := c.httpClient.Do(req)
	if err != nil {
		level.Error(log.Logger).Log("msg", "error getting delete requests from the store", "err", err)
		return nil, err
	}
	defer func() {
		_, _ = io.Copy(io.Discard, resp.Body)
		_ = resp.Body.Close()
	}()

	if resp.StatusCode/100 != 2 {
		err := fmt.Errorf("unexpected status code: %d", resp.StatusCode)
		level.Error(log.Logger).Log("msg", "error getting delete requests from the store", "err", err)
		return nil, err
	}

	var deleteRequests []deletion.DeleteRequest
	if err := json.NewDecoder(resp.Body).Decode(&deleteRequests); err != nil {
		level.Error(log.Logger).Log("msg", "error marshalling response", "err", err)
		return nil, err
	}

	return deleteRequests, nil
}

func (c *compactorHTTPClient) GetCacheGenerationNumber(ctx context.Context, userID string) (string, error) {
	req, err := http.NewRequestWithContext(ctx, http.MethodGet, c.cacheGenURL, nil)
	if err != nil {
		level.Error(log.Logger).Log("msg", "error getting cache gen numbers from the store", "err", err)
		return "", err
	}

	req.Header.Set(orgHeaderKey, userID)

	resp, err := c.httpClient.Do(req)
	if err != nil {
		level.Error(log.Logger).Log("msg", "error getting cache gen numbers from the store", "err", err)
		return "", err
	}
	defer resp.Body.Close()

	if resp.StatusCode < 200 || resp.StatusCode >= 300 {
		err := fmt.Errorf("unexpected status code: %d", resp.StatusCode)
		level.Error(log.Logger).Log("msg", "error getting cache gen numbers from the store", "err", err)
		return "", err
	}

	var genNumber string
	if err := json.NewDecoder(resp.Body).Decode(&genNumber); err != nil {
		level.Error(log.Logger).Log("msg", "error marshalling response", "err", err)
		return "", err
	}

	return genNumber, err
}