package updateagent

import (
	"context"
	"encoding/json"
	"errors"
	"io"
	"log/slog"
	"net/http"
	"strings"
	"sync"
	"time"

	"github.com/root-kdw12/hetzner-api-dyndns-records-webinterface/internal/buildinfo"
	"github.com/root-kdw12/hetzner-api-dyndns-records-webinterface/internal/updateprotocol"
)

type Runner interface {
	Update(context.Context, updateprotocol.Request, func(phase, message string)) error
}

type Controller struct {
	runner Runner
	logger *slog.Logger
	mu     sync.RWMutex
	status updateprotocol.Status
}

func NewController(runner Runner, logger *slog.Logger) *Controller {
	return &Controller{runner: runner, logger: logger, status: agentStatus(updateprotocol.PhaseIdle)}
}

func agentStatus(phase string) updateprotocol.Status {
	return updateprotocol.Status{
		Phase:         phase,
		AnonymousPull: true,
		UpdatedAt:     time.Now().UTC(),
		AgentVersion:  buildinfo.Version,
		Protocol:      buildinfo.UpdateProtocolVersion,
	}
}

func (c *Controller) Handler() http.Handler {
	mux := http.NewServeMux()
	mux.HandleFunc("GET /v1/status", c.statusHandler)
	mux.HandleFunc("POST /v1/update", c.updateHandler)
	return mux
}

func (c *Controller) statusHandler(w http.ResponseWriter, _ *http.Request) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.Header().Set("Cache-Control", "no-store")
	_ = json.NewEncoder(w).Encode(c.Status())
}

func (c *Controller) updateHandler(w http.ResponseWriter, r *http.Request) {
	r.Body = http.MaxBytesReader(w, r.Body, 32<<10)
	defer r.Body.Close()
	var request updateprotocol.Request
	decoder := json.NewDecoder(io.LimitReader(r.Body, 32<<10))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(&request); err != nil {
		http.Error(w, "invalid update request", http.StatusBadRequest)
		return
	}
	if err := decoder.Decode(&struct{}{}); !errors.Is(err, io.EOF) {
		http.Error(w, "invalid update request", http.StatusBadRequest)
		return
	}
	request.Version = strings.TrimSpace(request.Version)
	request.CurrentVersion = strings.TrimSpace(request.CurrentVersion)
	request.RegistryUsername = strings.TrimSpace(request.RegistryUsername)
	anonymous := request.RegistryUsername == "" && request.RegistryToken == ""
	credentialValid := request.RegistryUsername != "" && len(request.RegistryUsername) <= 128 && len(request.RegistryToken) >= 8 && len(request.RegistryToken) <= 1024
	if !updateprotocol.ValidVersion(request.Version) || !updateprotocol.ValidVersion(request.CurrentVersion) || (!anonymous && !credentialValid) {
		http.Error(w, "invalid update request", http.StatusBadRequest)
		return
	}
	if !c.begin(request.Version) {
		http.Error(w, "update already running", http.StatusConflict)
		return
	}
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(http.StatusAccepted)
	_, _ = w.Write([]byte("{\"accepted\":true}\n"))
	go c.run(request)
}

func (c *Controller) begin(version string) bool {
	c.mu.Lock()
	defer c.mu.Unlock()
	if c.status.Busy() {
		return false
	}
	now := time.Now().UTC()
	c.status = updateprotocol.Status{Phase: updateprotocol.PhaseQueued, TargetVersion: version, Message: "Update eingereiht", StartedAt: now, UpdatedAt: now, AgentVersion: buildinfo.Version, Protocol: buildinfo.UpdateProtocolVersion, AnonymousPull: true}
	return true
}

func (c *Controller) run(request updateprotocol.Request) {
	ctx, cancel := context.WithTimeout(context.Background(), 15*time.Minute)
	defer cancel()
	err := c.runner.Update(ctx, request, c.setPhase)
	registryCredential := request.RegistryToken
	request.RegistryToken = ""
	if err != nil {
		message := publicAgentError(err)
		c.setPhase(updateprotocol.PhaseFailed, message)
		c.logger.Error("software update failed", "version", request.Version, "error", redactSecret(err, registryCredential))
		return
	}
	c.setPhase(updateprotocol.PhaseComplete, "Update erfolgreich installiert")
	c.logger.Info("software update completed", "version", request.Version)
}

func redactSecret(err error, secret string) error {
	if err == nil || secret == "" || !strings.Contains(err.Error(), secret) {
		return err
	}
	return errors.New(strings.ReplaceAll(err.Error(), secret, "[redacted]"))
}

func (c *Controller) setPhase(phase, message string) {
	c.mu.Lock()
	c.status.Phase = phase
	c.status.Message = message
	c.status.UpdatedAt = time.Now().UTC()
	c.mu.Unlock()
}

func (c *Controller) Status() updateprotocol.Status {
	c.mu.RLock()
	defer c.mu.RUnlock()
	return c.status
}

func publicAgentError(err error) string {
	if err == nil {
		return "Update fehlgeschlagen"
	}
	var public interface{ PublicMessage() string }
	if errors.As(err, &public) {
		return public.PublicMessage()
	}
	return "Update fehlgeschlagen; der bisherige Container wurde wiederhergestellt"
}