// Package httpapi exposes the addrkit domain over a small, versioned JSON API.
//
// It contains no business logic: handlers decode requests, call the resolver
// and the outages source, and encode responses. Cross-cutting concerns
// (timeouts, recovery, request ids, logging) live in middleware.
package httpapi

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

	"git.totmin.ru/en2zmax/addrkit/internal/domain/address"
	"git.totmin.ru/en2zmax/addrkit/internal/domain/match"
	"git.totmin.ru/en2zmax/addrkit/internal/domain/outages"
)

// Resolver is the read side of the domain (implemented by *match.Resolver).
type Resolver interface {
	Resolve(ctx context.Context, raw string) match.Result
	Version() string
	Ready() bool
}

// Server wires the domain to HTTP.
type Server struct {
	resolver Resolver
	outages  outages.Source
	log      *slog.Logger
	now      func() time.Time
	loc      *time.Location
	timeout  time.Duration
}

// New builds a server. loc controls how outage dates are interpreted; it
// should be the operational timezone (Asia/Novosibirsk).
func New(resolver Resolver, src outages.Source, log *slog.Logger, loc *time.Location) *Server {
	if loc == nil {
		loc = time.UTC
	}
	return &Server{
		resolver: resolver,
		outages:  src,
		log:      log,
		now:      time.Now,
		loc:      loc,
		timeout:  10 * time.Second,
	}
}

// Handler returns the fully wrapped HTTP handler.
func (s *Server) Handler() http.Handler {
	mux := http.NewServeMux()
	mux.HandleFunc("POST /v1/resolve", s.handleResolve)
	mux.HandleFunc("POST /v1/outages", s.handleOutages)
	mux.HandleFunc("GET /v1/healthz", s.handleHealthz)
	mux.HandleFunc("GET /v1/readyz", s.handleReadyz)
	mux.HandleFunc("GET /v1/version", s.handleVersion)

	return recoverMW(s.log)(requestIDMW(loggingMW(s.log)(timeoutMW(s.timeout)(mux))))
}

type resolveRequest struct {
	Address string `json:"address"`
}

func (s *Server) handleResolve(w http.ResponseWriter, r *http.Request) {
	req, ok := s.decode(w, r)
	if !ok {
		return
	}
	writeJSON(w, http.StatusOK, s.resolver.Resolve(r.Context(), req.Address))
}

type outagesResponse struct {
	Status      address.Status   `json:"status"`
	Address     string           `json:"address,omitempty"`
	District    string           `json:"district,omitempty"`
	Outages     []outages.Outage `json:"outages,omitempty"`
	AsOf        string           `json:"as_of,omitempty"`
	DataVersion string           `json:"data_version,omitempty"`
}

func (s *Server) handleOutages(w http.ResponseWriter, r *http.Request) {
	req, ok := s.decode(w, r)
	if !ok {
		return
	}
	ctx := r.Context()
	res := s.resolver.Resolve(ctx, req.Address)

	out := outagesResponse{
		Status:      res.Status,
		Address:     res.Address,
		District:    res.District,
		DataVersion: res.DataVersion,
	}
	if res.Status != address.StatusFound {
		// No canonical address => nothing to query. Return the resolver's
		// verdict so the caller can ask for clarification.
		writeJSON(w, http.StatusOK, out)
		return
	}

	raw, err := s.outages.Query(ctx, res.Address)
	if err != nil {
		if errors.Is(err, context.DeadlineExceeded) || errors.Is(err, context.Canceled) {
			out.Status = address.StatusPortalTimeout
		} else {
			out.Status = address.StatusInfra
		}
		writeJSON(w, http.StatusOK, out)
		return
	}

	parsed := address.Parse(res.Address)
	current := outages.Current(raw, s.now(), s.loc)
	out.Outages = outages.MatchingHouse(current, parsed)
	out.AsOf = s.now().In(s.loc).Format(time.RFC3339)
	writeJSON(w, http.StatusOK, out)
}

func (s *Server) handleHealthz(w http.ResponseWriter, _ *http.Request) {
	writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
}

func (s *Server) handleReadyz(w http.ResponseWriter, _ *http.Request) {
	if !s.resolver.Ready() {
		writeJSON(w, http.StatusServiceUnavailable, map[string]string{"status": "not_ready"})
		return
	}
	writeJSON(w, http.StatusOK, map[string]string{"status": "ready"})
}

func (s *Server) handleVersion(w http.ResponseWriter, _ *http.Request) {
	writeJSON(w, http.StatusOK, map[string]string{"data_version": s.resolver.Version()})
}

// decode reads the JSON body into a resolveRequest, writing a 400 on failure.
func (s *Server) decode(w http.ResponseWriter, r *http.Request) (resolveRequest, bool) {
	var req resolveRequest
	r.Body = http.MaxBytesReader(w, r.Body, 64*1024)
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid json body")
		return resolveRequest{}, false
	}
	if req.Address == "" {
		writeError(w, http.StatusBadRequest, "address is required")
		return resolveRequest{}, false
	}
	return req, true
}

func writeJSON(w http.ResponseWriter, status int, v any) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(v)
}

func writeError(w http.ResponseWriter, status int, msg string) {
	writeJSON(w, status, map[string]any{"error": 1, "message": msg})
}