package api

import (
	"net/http"
	"strings"
	"time"

	"git.k8s-git-k6n.net/mats/fancy-dns/internal/localzone"
)

// The local-zone payloads are aliases rather than copies: the record, zone
// and delegation shapes are defined once in internal/localzone, where the
// writer produces them and the store's own snapshot test pins their fields.
// A copy here would be a second set of json tags to keep in step with the
// console, which is exactly the drift the contract tests in internal/app
// exist to catch.
type (
	// ZoneRecord is one authoritative record.
	ZoneRecord = localzone.Record
	// Zone is one compiled local zone.
	Zone = localzone.Zone
	// ZoneDelegation is a cut below an apex.
	ZoneDelegation = localzone.Delegation
)

// ZonesResponse is GET /api/zones.
//
// Every key is always present, and Types is the set of record types the write
// endpoints accept, so the console builds its type picker from the server
// instead of keeping its own list.
type ZonesResponse struct {
	// Zones are the compiled local zones, sorted by apex.
	Zones []localzone.Zone `json:"zones"`
	// Files are every master file the zones were compiled from.
	Files []string `json:"files"`
	// ManagedDir is the directory the API may rewrite, "" when the console
	// has no managed zone directory configured (blocklist.managed_zones).
	ManagedDir string `json:"managed_dir"`
	// Writable is whether a write to ManagedDir would succeed.
	Writable bool `json:"writable"`
	// Types are the record types the write endpoints accept.
	Types []string `json:"types"`
	// Records is the total number of records across every zone.
	Records int `json:"records"`
	// BuiltAt is when the zone store was compiled.
	BuiltAt time.Time `json:"built_at"`
	// Error is the reason the store is stale, "" when it is current. It is
	// here so a broken master file is visible in the console rather than
	// only in the log.
	Error string `json:"error"`
}

// ZoneRecordInput adds or replaces one record. A TTL of 0 means the zone's
// default, which is what a record written without a TTL column inherits.
type ZoneRecordInput struct {
	Zone  string `json:"zone"`
	Name  string `json:"name"`
	Type  string `json:"type"`
	TTL   uint32 `json:"ttl"`
	Value string `json:"value"`
}

// ZoneDelegationInput hands a name below an apex, and everything under it, to
// other servers.
type ZoneDelegationInput struct {
	Zone    string   `json:"zone"`
	Name    string   `json:"name"`
	Targets []string `json:"targets"`
	TTL     uint32   `json:"ttl"`
}

// ZoneWriteResponse is what a successful record or delegation change answers.
type ZoneWriteResponse struct {
	OK bool `json:"ok"`
	// Zone is the canonical apex the change landed in.
	Zone string `json:"zone"`
	// Serial is the zone's SOA serial after the write. It moves on every
	// change, so it is the cheapest way for the console to tell that what it
	// is looking at has been rewritten.
	Serial uint32 `json:"serial"`
	// Removed is set on a delete that matched something.
	Removed bool `json:"removed"`
}

// handleZones returns the compiled local zones.
func (s *Server) handleZones(w http.ResponseWriter, _ *http.Request) {
	if s.hooks.ListZones == nil {
		writeError(w, http.StatusNotImplemented, "local zones not available")
		return
	}
	v, err := s.hooks.ListZones()
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, v)
}

// handleZoneDelete removes a zone the console owns.
func (s *Server) handleZoneDelete(w http.ResponseWriter, r *http.Request) {
	if s.hooks.DeleteZone == nil {
		writeError(w, http.StatusNotImplemented, "local zones not available")
		return
	}
	zone := r.URL.Query().Get("zone")
	if zone == "" {
		writeError(w, http.StatusBadRequest, "zone is required")
		return
	}
	if err := s.hooks.DeleteZone(r.Context(), zone); err != nil {
		writeError(w, http.StatusNotFound, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, map[string]any{"ok": true, "zone": zone})
}

// handleZoneRecordAdd adds one record to a zone.
func (s *Server) handleZoneRecordAdd(w http.ResponseWriter, r *http.Request) {
	if s.hooks.AddZoneRecord == nil {
		writeError(w, http.StatusNotImplemented, "local zones not available")
		return
	}
	var in ZoneRecordInput
	if err := decodeJSON(r, &in); err != nil {
		writeError(w, http.StatusBadRequest, "malformed request body")
		return
	}
	if msg := validateZoneRecord(in); msg != "" {
		writeError(w, http.StatusBadRequest, msg)
		return
	}
	v, err := s.hooks.AddZoneRecord(r.Context(), in)
	if err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, v)
}

// handleZoneRecordPut replaces the RRset of one name and type.
func (s *Server) handleZoneRecordPut(w http.ResponseWriter, r *http.Request) {
	if s.hooks.PutZoneRecord == nil {
		writeError(w, http.StatusNotImplemented, "local zones not available")
		return
	}
	var in ZoneRecordInput
	if err := decodeJSON(r, &in); err != nil {
		writeError(w, http.StatusBadRequest, "malformed request body")
		return
	}
	if msg := validateZoneRecord(in); msg != "" {
		writeError(w, http.StatusBadRequest, msg)
		return
	}
	v, err := s.hooks.PutZoneRecord(r.Context(), in)
	if err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, v)
}

// handleZoneRecordDelete removes a record, or its whole RRset when no value is
// named.
func (s *Server) handleZoneRecordDelete(w http.ResponseWriter, r *http.Request) {
	if s.hooks.DeleteZoneRecord == nil {
		writeError(w, http.StatusNotImplemented, "local zones not available")
		return
	}
	zone := r.URL.Query().Get("zone")
	name := r.URL.Query().Get("name")
	rrtype := r.URL.Query().Get("type")
	if zone == "" || name == "" || rrtype == "" {
		writeError(w, http.StatusBadRequest, "zone, name and type are required")
		return
	}
	if err := s.hooks.DeleteZoneRecord(r.Context(), zone, name, rrtype, r.URL.Query().Get("value")); err != nil {
		writeError(w, http.StatusNotFound, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, map[string]any{"ok": true, "zone": zone, "name": name, "type": rrtype})
}

// handleZoneDelegationAdd delegates a name to other servers.
func (s *Server) handleZoneDelegationAdd(w http.ResponseWriter, r *http.Request) {
	if s.hooks.AddZoneDelegation == nil {
		writeError(w, http.StatusNotImplemented, "local zones not available")
		return
	}
	var in ZoneDelegationInput
	if err := decodeJSON(r, &in); err != nil {
		writeError(w, http.StatusBadRequest, "malformed request body")
		return
	}
	if strings.TrimSpace(in.Zone) == "" {
		writeError(w, http.StatusBadRequest, "zone is required")
		return
	}
	if strings.TrimSpace(in.Name) == "" {
		writeError(w, http.StatusBadRequest, "name is required")
		return
	}
	if len(in.Targets) == 0 {
		writeError(w, http.StatusBadRequest, "a delegation needs at least one NS target")
		return
	}
	v, err := s.hooks.AddZoneDelegation(r.Context(), in)
	if err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, v)
}

// handleZoneDelegationDelete removes a cut.
func (s *Server) handleZoneDelegationDelete(w http.ResponseWriter, r *http.Request) {
	if s.hooks.DeleteZoneDelegation == nil {
		writeError(w, http.StatusNotImplemented, "local zones not available")
		return
	}
	zone := r.URL.Query().Get("zone")
	name := r.URL.Query().Get("name")
	if zone == "" || name == "" {
		writeError(w, http.StatusBadRequest, "zone and name are required")
		return
	}
	if err := s.hooks.DeleteZoneDelegation(r.Context(), zone, name); err != nil {
		writeError(w, http.StatusNotFound, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, map[string]any{"ok": true, "zone": zone, "name": name})
}

// validateZoneRecord rejects an obviously incomplete record here so the
// console gets a message about the field rather than one about the zone file.
func validateZoneRecord(in ZoneRecordInput) string {
	if strings.TrimSpace(in.Zone) == "" {
		return "zone is required"
	}
	if strings.TrimSpace(in.Name) == "" {
		return "name is required"
	}
	if strings.TrimSpace(in.Type) == "" {
		return "type is required"
	}
	if strings.TrimSpace(in.Value) == "" {
		return "value is required"
	}
	return ""
}