// Package updatesocket exposes tera-updated only over a group-restricted Unix socket.
package updatesocket

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net"
	"net/http"
	"strconv"
	"time"

	"tera-clone/services/tera-api/internal/update"
)

const DefaultSocketPath = "/run/tera-updated/control.sock"

type response struct {
	Status *update.Status `json:"status,omitempty"`
	Code   string         `json:"code,omitempty"`
	Error  string         `json:"error,omitempty"`
}

type Server struct {
	Controller update.Controller
	MaxBytes   int64
}

func (s Server) Serve(listener net.Listener) error {
	if s.Controller == nil || s.MaxBytes <= 0 {
		return errors.New("update controller and positive package limit are required")
	}
	mux := http.NewServeMux()
	mux.HandleFunc("GET /v1/status", s.handleStatus)
	mux.HandleFunc("POST /v1/upload", s.handleUpload)
	mux.HandleFunc("POST /v1/apply", s.handleApply)
	server := &http.Server{Handler: mux, ReadHeaderTimeout: 5 * time.Second, IdleTimeout: 30 * time.Second}
	err := server.Serve(listener)
	if errors.Is(err, http.ErrServerClosed) || errors.Is(err, net.ErrClosed) {
		return nil
	}
	return err
}

func (s Server) handleStatus(w http.ResponseWriter, request *http.Request) {
	status, err := s.Controller.Status(request.Context())
	s.write(w, status, err)
}

func (s Server) handleUpload(w http.ResponseWriter, request *http.Request) {
	if request.ContentLength <= 0 || request.ContentLength > s.MaxBytes {
		s.write(w, update.Status{}, &update.Error{Code: "update_size_invalid", Message: "package content length is missing or exceeds the configured maximum"})
		return
	}
	request.Body = http.MaxBytesReader(w, request.Body, s.MaxBytes)
	status, err := s.Controller.Upload(request.Context(), update.UploadRequest{
		Filename: request.Header.Get("X-Tera-Filename"), ContentLength: request.ContentLength,
		Actor: request.Header.Get("X-Tera-Actor"), Body: request.Body,
	})
	s.write(w, status, err)
}

func (s Server) handleApply(w http.ResponseWriter, request *http.Request) {
	status, err := s.Controller.Apply(request.Context(), update.ApplyRequest{Actor: request.Header.Get("X-Tera-Actor"), OperationID: request.Header.Get("X-Tera-Operation-ID")})
	s.write(w, status, err)
}

func (Server) write(w http.ResponseWriter, status update.Status, err error) {
	w.Header().Set("Content-Type", "application/json")
	value := response{Status: &status}
	if err != nil {
		value.Code, value.Error = update.Code(err), err.Error()
		if value.Code == "" {
			value.Code = "update_failed"
		}
	}
	_ = json.NewEncoder(w).Encode(value)
}

type Client struct {
	uploadClient  *http.Client
	controlClient *http.Client
}

func NewClient(socketPath string) *Client {
	if socketPath == "" {
		socketPath = DefaultSocketPath
	}
	transport := &http.Transport{
		DialContext: func(ctx context.Context, _, _ string) (net.Conn, error) {
			dialer := net.Dialer{Timeout: 5 * time.Second}
			return dialer.DialContext(ctx, "unix", socketPath)
		},
		DisableKeepAlives: false,
	}
	return &Client{
		uploadClient:  &http.Client{Transport: transport},
		controlClient: &http.Client{Transport: transport, Timeout: 10 * time.Second},
	}
}

func (c *Client) Status(ctx context.Context) (update.Status, error) {
	request, _ := http.NewRequestWithContext(ctx, http.MethodGet, "http://tera-updated/v1/status", nil)
	return c.do(c.controlClient, request)
}

func (c *Client) Upload(ctx context.Context, value update.UploadRequest) (update.Status, error) {
	request, err := http.NewRequestWithContext(ctx, http.MethodPost, "http://tera-updated/v1/upload", io.NopCloser(value.Body))
	if err != nil {
		return update.Status{}, err
	}
	request.ContentLength = value.ContentLength
	request.Header.Set("Content-Type", "application/octet-stream")
	request.Header.Set("X-Tera-Filename", value.Filename)
	request.Header.Set("X-Tera-Actor", value.Actor)
	request.Header.Set("X-Tera-Content-Length", strconv.FormatInt(value.ContentLength, 10))
	return c.do(c.uploadClient, request)
}

func (c *Client) Apply(ctx context.Context, value update.ApplyRequest) (update.Status, error) {
	request, _ := http.NewRequestWithContext(ctx, http.MethodPost, "http://tera-updated/v1/apply", nil)
	request.Header.Set("X-Tera-Actor", value.Actor)
	request.Header.Set("X-Tera-Operation-ID", value.OperationID)
	return c.do(c.controlClient, request)
}

func (c *Client) do(client *http.Client, request *http.Request) (update.Status, error) {
	result, err := client.Do(request)
	if err != nil {
		return update.Status{}, &update.Error{Code: "update_unavailable", Message: "tera-updated is not reachable"}
	}
	defer result.Body.Close()
	var value response
	if err := json.NewDecoder(io.LimitReader(result.Body, 256*1024)).Decode(&value); err != nil {
		return update.Status{}, &update.Error{Code: "update_unavailable", Message: "tera-updated returned an invalid response"}
	}
	if value.Error != "" {
		return statusValue(value.Status), &update.Error{Code: value.Code, Message: value.Error}
	}
	if value.Status == nil {
		return update.Status{}, fmt.Errorf("tera-updated returned no status")
	}
	return *value.Status, nil
}

func statusValue(value *update.Status) update.Status {
	if value == nil {
		return update.Status{}
	}
	return *value
}