package keaapi

import (
	"context"
	"crypto/subtle"
	"encoding/json"
	"errors"
	"net/http"
	"strings"
	"time"

	"github.com/go-logr/logr"
)

// Server is the REST API exposing CRUD over KeaSubnet / KeaClientClass CRs.
type Server struct {
	Store Store
	Token string
	Log   logr.Logger
}

// Handler builds the routed http.Handler. Reads and writes are both token
// guarded (the whole surface mutates cluster state indirectly). Go 1.22+
// pattern routing gives chi-style method+path matching with no dependency.
func (s *Server) Handler() http.Handler {
	mux := http.NewServeMux()
	mux.HandleFunc("GET /healthz", func(w http.ResponseWriter, _ *http.Request) {
		w.WriteHeader(http.StatusOK)
		_, _ = w.Write([]byte("ok"))
	})

	mux.Handle("GET /api/v1/subnets", s.auth(http.HandlerFunc(s.listSubnets)))
	mux.Handle("GET /api/v1/subnets/{name}", s.auth(http.HandlerFunc(s.getSubnet)))
	mux.Handle("PUT /api/v1/subnets/{name}", s.auth(http.HandlerFunc(s.putSubnet)))
	mux.Handle("DELETE /api/v1/subnets/{name}", s.auth(http.HandlerFunc(s.deleteSubnet)))

	mux.Handle("GET /api/v1/clientclasses", s.auth(http.HandlerFunc(s.listClasses)))
	mux.Handle("GET /api/v1/clientclasses/{name}", s.auth(http.HandlerFunc(s.getClass)))
	mux.Handle("PUT /api/v1/clientclasses/{name}", s.auth(http.HandlerFunc(s.putClass)))
	mux.Handle("DELETE /api/v1/clientclasses/{name}", s.auth(http.HandlerFunc(s.deleteClass)))

	return mux
}

// ListenAndServe runs the server until ctx is cancelled.
func (s *Server) ListenAndServe(ctx context.Context, addr string) error {
	srv := &http.Server{Addr: addr, Handler: s.Handler(), ReadHeaderTimeout: 10 * time.Second}
	go func() {
		<-ctx.Done()
		shutdownCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		defer cancel()
		_ = srv.Shutdown(shutdownCtx)
	}()
	if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
		return err
	}
	return nil
}

func (s *Server) auth(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if s.Token == "" {
			writeError(w, http.StatusServiceUnavailable, "auth disabled: KEA_API_TOKEN not set")
			return
		}
		presented := bearer(r)
		if presented == "" || subtle.ConstantTimeCompare([]byte(presented), []byte(s.Token)) != 1 {
			writeError(w, http.StatusUnauthorized, "invalid or missing token")
			return
		}
		next.ServeHTTP(w, r)
	})
}

func bearer(r *http.Request) string {
	if h := r.Header.Get("Authorization"); h != "" {
		if after, ok := strings.CutPrefix(h, "Bearer "); ok {
			return after
		}
	}
	return r.Header.Get("token")
}

// ---- subnet handlers ----

func (s *Server) listSubnets(w http.ResponseWriter, r *http.Request) {
	items, err := s.Store.ListSubnets(r.Context())
	if err != nil {
		s.fail(w, err)
		return
	}
	writeJSON(w, http.StatusOK, items)
}

func (s *Server) getSubnet(w http.ResponseWriter, r *http.Request) {
	item, err := s.Store.GetSubnet(r.Context(), r.PathValue("name"))
	if err != nil {
		s.fail(w, err)
		return
	}
	writeJSON(w, http.StatusOK, item)
}

func (s *Server) putSubnet(w http.ResponseWriter, r *http.Request) {
	var in SubnetAPI
	if err := json.NewDecoder(r.Body).Decode(&in); err != nil {
		writeError(w, http.StatusBadRequest, "invalid JSON: "+err.Error())
		return
	}
	in.Name = r.PathValue("name")
	if in.Subnet == "" {
		writeError(w, http.StatusBadRequest, "subnet is required")
		return
	}
	out, err := s.Store.UpsertSubnet(r.Context(), in)
	if err != nil {
		s.fail(w, err)
		return
	}
	writeJSON(w, http.StatusOK, out)
}

func (s *Server) deleteSubnet(w http.ResponseWriter, r *http.Request) {
	if err := s.Store.DeleteSubnet(r.Context(), r.PathValue("name")); err != nil {
		s.fail(w, err)
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

// ---- client class handlers ----

func (s *Server) listClasses(w http.ResponseWriter, r *http.Request) {
	items, err := s.Store.ListClasses(r.Context())
	if err != nil {
		s.fail(w, err)
		return
	}
	writeJSON(w, http.StatusOK, items)
}

func (s *Server) getClass(w http.ResponseWriter, r *http.Request) {
	item, err := s.Store.GetClass(r.Context(), r.PathValue("name"))
	if err != nil {
		s.fail(w, err)
		return
	}
	writeJSON(w, http.StatusOK, item)
}

func (s *Server) putClass(w http.ResponseWriter, r *http.Request) {
	var in ClientClassAPI
	if err := json.NewDecoder(r.Body).Decode(&in); err != nil {
		writeError(w, http.StatusBadRequest, "invalid JSON: "+err.Error())
		return
	}
	in.Name = r.PathValue("name")
	if in.Test == "" && len(in.ArchHex) == 0 {
		writeError(w, http.StatusBadRequest, "either test or arch_hex is required")
		return
	}
	out, err := s.Store.UpsertClass(r.Context(), in)
	if err != nil {
		s.fail(w, err)
		return
	}
	writeJSON(w, http.StatusOK, out)
}

func (s *Server) deleteClass(w http.ResponseWriter, r *http.Request) {
	if err := s.Store.DeleteClass(r.Context(), r.PathValue("name")); err != nil {
		s.fail(w, err)
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

func (s *Server) fail(w http.ResponseWriter, err error) {
	if errors.Is(err, ErrNotFound) {
		writeError(w, http.StatusNotFound, "not found")
		return
	}
	s.Log.Error(err, "request failed")
	writeError(w, http.StatusInternalServerError, err.Error())
}

func writeJSON(w http.ResponseWriter, status int, v any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(v)
}

func writeError(w http.ResponseWriter, status int, msg string) {
	writeJSON(w, status, map[string]string{"error": msg})
}