package api

import (
	"encoding/json"
	"errors"
	"io"
	"log"
	"net/http"

	"github.com/go-chi/chi/v5"
	"github.com/google/uuid"

	"github.com/vasyakrg/dns-autoresolver/internal/model"
	"github.com/vasyakrg/dns-autoresolver/internal/service"
	"github.com/vasyakrg/dns-autoresolver/internal/store/dto"
	"github.com/vasyakrg/dns-autoresolver/internal/tmpl"
)

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

func (a *API) handleCheck(w http.ResponseWriter, r *http.Request) {
	// pid is guaranteed present and owned by the caller — RequireProjectAccess
	// validated it before this handler ever runs.
	pid, _ := projectIDFrom(r.Context())
	did, err := uuid.Parse(chi.URLParam(r, "did"))
	if err != nil {
		writeErr(w, http.StatusBadRequest, "invalid domain id")
		return
	}
	cs, err := a.Svc.Check(r.Context(), pid, did)
	if err != nil {
		// Persist the failure so the domain badge reflects it instead of stale
		// "unknown"; the write error (if any) is logged, never masks the 500.
		if serr := a.Store.SetDomainStatus(r.Context(), did, pid, service.StatusError); serr != nil {
			log.Printf("api: set domain status (error) failed: %v", serr)
		}
		log.Printf("api: check failed: %v", err)
		// A provider failure (e.g. Selectel returning a 409 conflict) is safe
		// and useful to show the user as-is; any other failure (decrypt/db/loader)
		// stays a generic "internal error" to avoid leaking internals.
		if errors.Is(err, service.ErrProviderUnavailable) {
			writeErr(w, http.StatusBadGateway, service.ProviderMessage(err))
		} else {
			writeErr(w, http.StatusInternalServerError, "internal error")
		}
		return
	}
	// Manual check persists status/history only — no notification. Notify
	// remains the scheduler's responsibility (see internal/scheduler).
	if serr := a.Store.SetDomainStatus(r.Context(), did, pid, service.DeriveStatus(cs)); serr != nil {
		log.Printf("api: set domain status failed: %v", serr)
	}
	writeJSON(w, http.StatusOK, toChangesetResponse(cs))
}

func (a *API) handleApply(w http.ResponseWriter, r *http.Request) {
	// pid is guaranteed present and owned by the caller — RequireProjectAccess
	// validated it before this handler ever runs.
	pid, _ := projectIDFrom(r.Context())
	did, err := uuid.Parse(chi.URLParam(r, "did"))
	if err != nil {
		writeErr(w, http.StatusBadRequest, "invalid domain id")
		return
	}
	var req applyRequest
	if r.Body != nil {
		r.Body = http.MaxBytesReader(w, r.Body, 1<<20) // 1 MiB
		// пустое тело допустимо → значения по умолчанию (пустые списки, ничего
		// не применяется); любая другая ошибка decode (битый JSON, неверные
		// типы) → 400
		if err := json.NewDecoder(r.Body).Decode(&req); err != nil && !errors.Is(err, io.EOF) {
			writeErr(w, http.StatusBadRequest, "invalid request body")
			return
		}
	}
	cs, err := a.Svc.Apply(r.Context(), pid, did, service.ApplyRequest{
		Updates: req.Updates, Prunes: req.Prunes,
	})
	if err != nil {
		log.Printf("api: apply failed: %v", err)
		// Same distinction as handleCheck: surface the real provider message,
		// keep everything else generic.
		if errors.Is(err, service.ErrProviderUnavailable) {
			writeErr(w, http.StatusBadGateway, service.ProviderMessage(err))
		} else {
			writeErr(w, http.StatusInternalServerError, "internal error")
		}
		return
	}
	writeJSON(w, http.StatusOK, toChangesetResponse(cs))
}

// handleZoneRecords reads a zone's current records straight from the
// provider — no template required, no diff computed. Backs read-only zone
// viewing for domains that don't have a template attached (yet).
func (a *API) handleZoneRecords(w http.ResponseWriter, r *http.Request) {
	pid, _ := projectIDFrom(r.Context())
	did, err := uuid.Parse(chi.URLParam(r, "did"))
	if err != nil {
		writeErr(w, http.StatusBadRequest, "invalid domain id")
		return
	}
	recs, err := a.Svc.ZoneRecords(r.Context(), pid, did)
	if err != nil {
		log.Printf("api: zone records failed: %v", err)
		if errors.Is(err, service.ErrProviderUnavailable) {
			writeErr(w, http.StatusBadGateway, "не удалось получить записи зоны у провайдера")
		} else {
			writeErr(w, http.StatusNotFound, "домен не найден")
		}
		return
	}
	doc := dto.FromModel(recs)
	writeJSON(w, http.StatusOK, doc.Records) // []dto.RecordDTO
}

// handleTemplateFromZone snapshots a zone's current managed records (NS/SOA
// excluded — they're read-only, never part of a template) into a brand new
// template, then auto-attaches it to the domain so check/apply become
// available immediately.
func (a *API) handleTemplateFromZone(w http.ResponseWriter, r *http.Request) {
	pid, _ := projectIDFrom(r.Context())
	did, err := uuid.Parse(chi.URLParam(r, "did"))
	if err != nil {
		writeErr(w, http.StatusBadRequest, "invalid domain id")
		return
	}
	dom, err := a.Store.GetDomain(r.Context(), did, pid)
	if err != nil {
		log.Printf("api: template-from-zone: get domain failed: %v", err)
		writeErr(w, http.StatusNotFound, "домен не найден")
		return
	}
	// This endpoint only makes sense for a domain with no template attached
	// yet — it snapshots the zone's live state into a brand-new template.
	// If a template is already bound, re-attaching a fresh snapshot would
	// silently orphan the existing one; re-pointing a domain to a different
	// template is a separate, explicit action and must not happen as a side
	// effect of a retried/duplicate POST here.
	if dom.TemplateID != nil {
		writeErr(w, http.StatusConflict, "шаблон уже привязан")
		return
	}
	recs, err := a.Svc.ZoneRecords(r.Context(), pid, did)
	if err != nil {
		log.Printf("api: template-from-zone: zone records failed: %v", err)
		if errors.Is(err, service.ErrProviderUnavailable) {
			writeErr(w, http.StatusBadGateway, "не удалось получить записи зоны у провайдера")
		} else {
			writeErr(w, http.StatusNotFound, "домен не найден")
		}
		return
	}
	// Snapshot only managed records — NS/SOA are read-only and never templated.
	managed := make([]model.Record, 0, len(recs))
	for _, rc := range recs {
		if rc.Type.Managed() {
			managed = append(managed, rc)
		}
	}
	doc := tmpl.Parameterize(managed, dom.ZoneName)
	tpl, err := a.Store.CreateTemplate(r.Context(), pid, dom.ZoneName+" snapshot", doc)
	if err != nil {
		log.Printf("api: template-from-zone: create template failed: %v", err)
		writeErr(w, http.StatusInternalServerError, "internal error")
		return
	}
	if _, err := a.Store.SetDomainTemplate(r.Context(), did, pid, &tpl.ID); err != nil {
		log.Printf("api: template-from-zone: attach template failed: %v", err)
		writeErr(w, http.StatusInternalServerError, "internal error")
		return
	}
	writeJSON(w, http.StatusCreated, toTemplateResponse(tpl))
}