// SPDX-License-Identifier: GPL-2.0-or-later
// Copyright (C) 2026 Bryan Joshua Pedini

package main

import (
	"encoding/json"
	"net/http"
	"sort"
	"strconv"
	"strings"

	"github.com/gorilla/mux"
)

// pdnsZone is the zone-list entry shape.
type pdnsZone struct {
	ID   string `json:"id"`
	Name string `json:"name"`
	URL  string `json:"url"`
	Kind string `json:"kind"`
}

// pdnsRecord is one record within an rrset. Field order matches PowerDNS.
type pdnsRecord struct {
	Content  string `json:"content"`
	Disabled bool   `json:"disabled"`
}

// pdnsRRset is one rrset. Field order MUST be name, type, ttl, records —
// acme.sh regex-scrapes the zone-detail JSON expecting "name" before
// "records".
type pdnsRRset struct {
	Name    string       `json:"name"`
	Type    string       `json:"type"`
	TTL     int          `json:"ttl"`
	Records []pdnsRecord `json:"records"`
}

// pdnsZoneDetail is the zone-detail response shape.
type pdnsZoneDetail struct {
	ID     string      `json:"id"`
	Name   string      `json:"name"`
	Kind   string      `json:"kind"`
	URL    string      `json:"url"`
	RRsets []pdnsRRset `json:"rrsets"`
}

// checkServerID returns false and writes a 404 if server_id doesn't match
// the configured PDNS_SERVER_ID. Cross-cutting per SEMANTICS §5.
func (s *WebServer) checkServerID(w http.ResponseWriter, r *http.Request) bool {
	if mux.Vars(r)["server_id"] != s.Config.PDNSServerID {
		writeJSONError(w, http.StatusNotFound, "Not Found")
		return false
	}
	return true
}

// canonicalZone lowercases and ensures a trailing dot, per SEMANTICS §4.
func canonicalZone(zoneID string) string {
	zone := strings.ToLower(zoneID)
	if !strings.HasSuffix(zone, ".") {
		zone += "."
	}
	return zone
}

// handleListZones implements GET /api/v1/servers/{server_id}/zones.
func (s *WebServer) handleListZones(w http.ResponseWriter, r *http.Request) {
	if !s.checkServerID(w, r) {
		return
	}

	zones, err := s.Store.ListZones(r.Context())
	if err != nil {
		s.Logger.Error("list zones failed", "error", err)
		writeJSONError(w, http.StatusInternalServerError, "internal error")
		return
	}

	serverID := mux.Vars(r)["server_id"]
	out := make([]pdnsZone, 0, len(zones))
	for _, zone := range zones {
		out = append(out, pdnsZone{
			ID:   zone,
			Name: zone,
			URL:  "/api/v1/servers/" + serverID + "/zones/" + zone,
			Kind: "Native",
		})
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(out)
}

// soaContent is the type-specific content shape for SOA rows.
type soaContent struct {
	TTL     int    `json:"ttl"`
	Mbox    string `json:"mbox"`
	NS      string `json:"ns"`
	Refresh int    `json:"refresh"`
	Retry   int    `json:"retry"`
	Expire  int    `json:"expire"`
}

// rrsetContent renders the pdns rrset "content" string for one row per
// SEMANTICS §4's mapping table. Unparsable/unknown content is emitted raw,
// never dropped.
func rrsetContent(recordType, content string) string {
	switch recordType {
	case "TXT":
		var c struct {
			Text string `json:"text"`
		}
		if err := json.Unmarshal([]byte(content), &c); err != nil {
			return content
		}
		return `"` + c.Text + `"`
	case "A", "AAAA":
		var c struct {
			IP string `json:"ip"`
		}
		if err := json.Unmarshal([]byte(content), &c); err != nil {
			return content
		}
		return c.IP
	case "CNAME", "NS":
		var c struct {
			Host string `json:"host"`
		}
		if err := json.Unmarshal([]byte(content), &c); err != nil {
			return content
		}
		return c.Host
	case "SOA":
		var c soaContent
		if err := json.Unmarshal([]byte(content), &c); err != nil {
			return content
		}
		ttl := c.TTL
		if ttl == 0 {
			ttl = 300
		}
		return c.NS + " " + c.Mbox + " 0 " +
			strconv.Itoa(c.Refresh) + " " + strconv.Itoa(c.Retry) + " " +
			strconv.Itoa(c.Expire) + " " + strconv.Itoa(ttl)
	default:
		return content
	}
}

// rrsetKey groups rows by (name, record_type).
type rrsetKey struct {
	name       string
	recordType string
}

// handleZoneDetail implements GET /api/v1/servers/{server_id}/zones/{zone_id}.
func (s *WebServer) handleZoneDetail(w http.ResponseWriter, r *http.Request) {
	if !s.checkServerID(w, r) {
		return
	}

	vars := mux.Vars(r)
	zone := canonicalZone(vars["zone_id"])

	records, err := s.Store.GetZoneRecords(r.Context(), zone)
	if err != nil {
		s.Logger.Error("get zone records failed", "error", err)
		writeJSONError(w, http.StatusInternalServerError, "internal error")
		return
	}
	if len(records) == 0 {
		writeJSONError(w, http.StatusNotFound, "Not Found")
		return
	}

	groups := make(map[rrsetKey][]Record)
	var order []rrsetKey
	for _, rec := range records {
		key := rrsetKey{name: rec.Name, recordType: rec.RecordType}
		if _, ok := groups[key]; !ok {
			order = append(order, key)
		}
		groups[key] = append(groups[key], rec)
	}
	sort.Slice(order, func(i, j int) bool {
		if order[i].name != order[j].name {
			return order[i].name < order[j].name
		}
		return order[i].recordType < order[j].recordType
	})

	rrsets := make([]pdnsRRset, 0, len(order))
	for _, key := range order {
		rows := groups[key]
		fqdn := zone
		if key.name != "" {
			fqdn = key.name + "." + zone
		}

		ttl := 300
		for _, rec := range rows {
			if rec.TTL.Valid {
				ttl = int(rec.TTL.Int64)
				break
			}
		}

		recs := make([]pdnsRecord, 0, len(rows))
		for _, rec := range rows {
			recs = append(recs, pdnsRecord{
				Content:  rrsetContent(rec.RecordType, rec.Content),
				Disabled: false,
			})
		}

		rrsets = append(rrsets, pdnsRRset{
			Name:    fqdn,
			Type:    key.recordType,
			TTL:     ttl,
			Records: recs,
		})
	}

	serverID := vars["server_id"]
	detail := pdnsZoneDetail{
		ID:     zone,
		Name:   zone,
		Kind:   "Native",
		URL:    "/api/v1/servers/" + serverID + "/zones/" + zone,
		RRsets: rrsets,
	}

	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(detail)
}

// patchRecord is one record entry within a PATCH rrset.
type patchRecord struct {
	Content  string `json:"content"`
	Disabled bool   `json:"disabled"`
}

// patchRRset is one rrset entry within a PATCH request body.
type patchRRset struct {
	Name       string        `json:"name"`
	Type       string        `json:"type"`
	TTL        int           `json:"ttl"`
	ChangeType string        `json:"changetype"`
	Records    []patchRecord `json:"records"`
}

// patchRequest is the PATCH zone body.
type patchRequest struct {
	RRsets []patchRRset `json:"rrsets"`
}

// unq strips exactly one leading and one trailing double quote, if present.
func unq(c string) string {
	if len(c) >= 1 && strings.HasPrefix(c, `"`) {
		c = c[1:]
	}
	if len(c) >= 1 && strings.HasSuffix(c, `"`) {
		c = c[:len(c)-1]
	}
	return c
}

// recordContent marshals the type-specific content JSON for storage, per
// SEMANTICS §4. supportedTypes lists what this handler accepts.
func recordContent(recordType, apiContent string) (string, bool) {
	switch recordType {
	case "TXT":
		b, err := json.Marshal(map[string]string{"text": unq(apiContent)})
		if err != nil {
			return "", false
		}
		return string(b), true
	case "A", "AAAA":
		b, err := json.Marshal(map[string]string{"ip": apiContent})
		if err != nil {
			return "", false
		}
		return string(b), true
	case "CNAME", "NS":
		b, err := json.Marshal(map[string]string{"host": apiContent})
		if err != nil {
			return "", false
		}
		return string(b), true
	default:
		return "", false
	}
}

// handleZonePatch implements PATCH /api/v1/servers/{server_id}/zones/{zone_id}.
func (s *WebServer) handleZonePatch(w http.ResponseWriter, r *http.Request) {
	if !s.checkServerID(w, r) {
		return
	}

	vars := mux.Vars(r)
	zone := canonicalZone(vars["zone_id"])

	exists, err := s.Store.ZoneExists(r.Context(), zone)
	if err != nil {
		s.Logger.Error("zone exists check failed", "error", err)
		writeJSONError(w, http.StatusInternalServerError, "internal error")
		return
	}
	if !exists {
		writeJSONError(w, http.StatusNotFound, "Not Found")
		return
	}

	var body patchRequest
	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
		writeJSONError(w, http.StatusUnprocessableEntity, "malformed JSON body")
		return
	}

	changes := make([]RRsetChange, 0, len(body.RRsets))
	for _, rrset := range body.RRsets {
		if rrset.ChangeType != "REPLACE" && rrset.ChangeType != "DELETE" {
			writeJSONError(w, http.StatusUnprocessableEntity, "unknown or missing changetype")
			return
		}
		if rrset.Name == "" || rrset.Type == "" {
			writeJSONError(w, http.StatusUnprocessableEntity, "missing name or type")
			return
		}

		name := strings.ToLower(rrset.Name)
		if !strings.HasSuffix(name, ".") {
			name += "."
		}
		if name != zone && !strings.HasSuffix(name, "."+zone) {
			writeJSONError(w, http.StatusUnprocessableEntity, "name is not part of zone")
			return
		}
		rel := strings.TrimSuffix(name, zone)
		rel = strings.TrimSuffix(rel, ".")

		change := RRsetChange{
			Zone:       zone,
			Name:       rel,
			RecordType: rrset.Type,
			ChangeType: rrset.ChangeType,
		}

		if rrset.ChangeType == "REPLACE" {
			if len(rrset.Records) == 0 {
				writeJSONError(w, http.StatusUnprocessableEntity, "REPLACE requires at least one record")
				return
			}

			ttl := rrset.TTL
			if ttl <= 0 {
				ttl = s.Config.DefaultTTL
			}
			change.TTL = ttl

			contents := make([]string, 0, len(rrset.Records))
			for _, rec := range rrset.Records {
				content, ok := recordContent(rrset.Type, rec.Content)
				if !ok {
					writeJSONError(w, http.StatusUnprocessableEntity, "unsupported record type")
					return
				}
				contents = append(contents, content)
			}
			change.Contents = contents
		}

		changes = append(changes, change)
	}

	if err := s.Store.ApplyRRsets(r.Context(), changes); err != nil {
		s.Logger.Error("apply rrsets failed", "error", err)
		writeJSONError(w, http.StatusInternalServerError, "internal error")
		return
	}

	w.WriteHeader(http.StatusNoContent)
}

// handleZoneNotify implements PUT /api/v1/servers/{server_id}/zones/{zone_id}/notify.
func (s *WebServer) handleZoneNotify(w http.ResponseWriter, r *http.Request) {
	if !s.checkServerID(w, r) {
		return
	}

	vars := mux.Vars(r)
	zone := canonicalZone(vars["zone_id"])

	exists, err := s.Store.ZoneExists(r.Context(), zone)
	if err != nil {
		s.Logger.Error("zone exists check failed", "error", err)
		writeJSONError(w, http.StatusInternalServerError, "internal error")
		return
	}
	if !exists {
		writeJSONError(w, http.StatusNotFound, "Not Found")
		return
	}

	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(http.StatusOK)
	json.NewEncoder(w).Encode(map[string]string{"result": "Notification queued"})
}