package server

import (
	"encoding/json"
	"errors"
	"net/http"
	"strconv"

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

	"git.unkin.net/unkin/tomswallapi/internal/compiler"
	"git.unkin.net/unkin/tomswallapi/internal/model"
	"git.unkin.net/unkin/tomswallapi/internal/store"
)

// mountResources wires the Terraform-facing CRUD endpoints. Resources with a
// dedicated repository method are wired here; the long-tail per-device sections
// (providers, tc, etc.) are added as their storage lands.
func (s *Server) mountResources(r chi.Router) {
	r.Get("/generation", s.handleGeneration)

	r.Route("/fabrics", func(r chi.Router) {
		r.Get("/", s.listFabrics)
		r.Get("/{name}", s.getFabric)
		r.Put("/{name}", s.putFabric)
		r.Delete("/{name}", s.deleteFabric)
	})
	r.Route("/zones", func(r chi.Router) {
		r.Get("/", s.listZones)
		r.Get("/{name}", s.getZone)
		r.Put("/{name}", s.putZone)
		r.Delete("/{name}", s.deleteZone)
	})
	r.Route("/address-groups", func(r chi.Router) {
		r.Get("/", s.listAddressGroups)
		r.Get("/{name}", s.getAddressGroup)
		r.Put("/{name}", s.putAddressGroup)
		r.Delete("/{name}", s.deleteAddressGroup)
	})
	r.Route("/devices", func(r chi.Router) {
		r.Get("/", s.listDevices)
		r.Get("/{name}", s.getDevice)
		r.Put("/{name}", s.putDevice)
		r.Delete("/{name}", s.deleteDevice)
		r.Get("/{name}/bindings", s.listBindings)
		r.Get("/{name}/bindings/{zone}", s.getBinding)
		r.Put("/{name}/bindings/{zone}", s.putBinding)
		r.Delete("/{name}/bindings/{zone}", s.deleteBinding)
	})
	r.Route("/portgroups", func(r chi.Router) {
		r.Get("/", s.listPortGroups)
		r.Get("/{name}", s.getPortGroup)
		r.Put("/{name}", s.putPortGroup)
		r.Delete("/{name}", s.deletePortGroup)
	})
	r.Route("/rules", func(r chi.Router) {
		r.Get("/", s.listRules)
		r.Post("/", s.createRule)
		r.Get("/{id}", s.getRule)
		r.Delete("/{id}", s.deleteRule)
	})
	s.mountNAT(r)
}

// respondOne writes a single resource, mapping ErrNotFound to 404.
func respondOne(w http.ResponseWriter, v any, err error) {
	if err != nil {
		if errors.Is(err, store.ErrNotFound) {
			writeError(w, http.StatusNotFound, "not found")
			return
		}
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, v)
}

// respondDelete maps a delete result to 204/404/500.
func respondDelete(w http.ResponseWriter, err error) {
	if err != nil {
		if errors.Is(err, store.ErrNotFound) {
			writeError(w, http.StatusNotFound, "not found")
			return
		}
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

func (s *Server) listPortGroups(w http.ResponseWriter, r *http.Request) {
	list, err := s.store.ListPortGroups(r.Context())
	respondList(w, list, err)
}

func (s *Server) putPortGroup(w http.ResponseWriter, r *http.Request) {
	var p model.PortGroup
	if !decode(w, r, &p) {
		return
	}
	p.Name = chi.URLParam(r, "name")
	if err := s.store.UpsertPortGroup(r.Context(), p); err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, p)
}

func (s *Server) handleGeneration(w http.ResponseWriter, r *http.Request) {
	g, err := s.store.Generation(r.Context())
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, map[string]int64{"generation": g})
}

// ---- Fabrics ---------------------------------------------------------------

func (s *Server) listFabrics(w http.ResponseWriter, r *http.Request) {
	list, err := s.store.ListFabrics(r.Context())
	respondList(w, list, err)
}

func (s *Server) putFabric(w http.ResponseWriter, r *http.Request) {
	var f model.Fabric
	if !decode(w, r, &f) {
		return
	}
	f.Name = chi.URLParam(r, "name")
	if err := s.store.UpsertFabric(r.Context(), f); err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, f)
}

// ---- Zones -----------------------------------------------------------------

func (s *Server) listZones(w http.ResponseWriter, r *http.Request) {
	list, err := s.store.ListZones(r.Context())
	respondList(w, list, err)
}

func (s *Server) putZone(w http.ResponseWriter, r *http.Request) {
	var z model.Zone
	if !decode(w, r, &z) {
		return
	}
	z.Name = chi.URLParam(r, "name")
	if err := s.store.UpsertZone(r.Context(), z); err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, z)
}

// ---- Address groups --------------------------------------------------------

func (s *Server) listAddressGroups(w http.ResponseWriter, r *http.Request) {
	list, err := s.store.ListAddressGroups(r.Context())
	respondList(w, list, err)
}

func (s *Server) putAddressGroup(w http.ResponseWriter, r *http.Request) {
	var g model.AddressGroup
	if !decode(w, r, &g) {
		return
	}
	g.Name = chi.URLParam(r, "name")
	if g.Type != model.GroupStatic && g.Type != model.GroupDNS && g.Type != model.GroupASN {
		writeError(w, http.StatusBadRequest, "type must be one of: static, dns, asn")
		return
	}
	if err := s.store.UpsertAddressGroup(r.Context(), g); err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, g)
}

// ---- Devices & bindings ----------------------------------------------------

func (s *Server) listDevices(w http.ResponseWriter, r *http.Request) {
	list, err := s.store.ListDevices(r.Context())
	respondList(w, list, err)
}

func (s *Server) putDevice(w http.ResponseWriter, r *http.Request) {
	var d model.Device
	if !decode(w, r, &d) {
		return
	}
	d.Name = chi.URLParam(r, "name")
	if d.Class != model.ClassRouter && d.Class != model.ClassFirewall {
		writeError(w, http.StatusBadRequest, "class must be one of: router, firewall")
		return
	}
	if err := s.store.UpsertDevice(r.Context(), d); err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, d)
}

func (s *Server) listBindings(w http.ResponseWriter, r *http.Request) {
	list, err := s.store.ListBindings(r.Context(), chi.URLParam(r, "name"))
	respondList(w, list, err)
}

func (s *Server) putBinding(w http.ResponseWriter, r *http.Request) {
	var b model.Binding
	if !decode(w, r, &b) {
		return
	}
	b.Device = chi.URLParam(r, "name")
	b.Zone = chi.URLParam(r, "zone")
	if err := s.store.UpsertBinding(r.Context(), b); err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, b)
}

// ---- Rules -----------------------------------------------------------------

func (s *Server) listRules(w http.ResponseWriter, r *http.Request) {
	list, err := s.store.ListRules(r.Context())
	respondList(w, list, err)
}

func (s *Server) createRule(w http.ResponseWriter, r *http.Request) {
	var rule model.Rule
	if !decode(w, r, &rule) {
		return
	}
	id, err := s.store.CreateRule(r.Context(), rule)
	if err != nil {
		// Grammar/validation failures are client errors.
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}
	rule.ID = id
	writeJSON(w, http.StatusCreated, rule)
}

func (s *Server) deleteRule(w http.ResponseWriter, r *http.Request) {
	id, err := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
	if err != nil {
		writeError(w, http.StatusBadRequest, "id must be an integer")
		return
	}
	if err := s.store.DeleteRule(r.Context(), id); err != nil {
		if errors.Is(err, store.ErrNotFound) {
			writeError(w, http.StatusNotFound, "rule not found")
			return
		}
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

// ---- Get-single and Delete handlers ----------------------------------------

func (s *Server) getFabric(w http.ResponseWriter, r *http.Request) {
	f, err := s.store.GetFabric(r.Context(), chi.URLParam(r, "name"))
	respondOne(w, f, err)
}

func (s *Server) deleteFabric(w http.ResponseWriter, r *http.Request) {
	respondDelete(w, s.store.DeleteFabric(r.Context(), chi.URLParam(r, "name")))
}

func (s *Server) getZone(w http.ResponseWriter, r *http.Request) {
	z, err := s.store.GetZone(r.Context(), chi.URLParam(r, "name"))
	respondOne(w, z, err)
}

func (s *Server) deleteZone(w http.ResponseWriter, r *http.Request) {
	respondDelete(w, s.store.DeleteZone(r.Context(), chi.URLParam(r, "name")))
}

func (s *Server) getAddressGroup(w http.ResponseWriter, r *http.Request) {
	g, err := s.store.GetAddressGroup(r.Context(), chi.URLParam(r, "name"))
	respondOne(w, g, err)
}

func (s *Server) deleteAddressGroup(w http.ResponseWriter, r *http.Request) {
	respondDelete(w, s.store.DeleteAddressGroup(r.Context(), chi.URLParam(r, "name")))
}

func (s *Server) getPortGroup(w http.ResponseWriter, r *http.Request) {
	p, err := s.store.GetPortGroup(r.Context(), chi.URLParam(r, "name"))
	respondOne(w, p, err)
}

func (s *Server) deletePortGroup(w http.ResponseWriter, r *http.Request) {
	respondDelete(w, s.store.DeletePortGroup(r.Context(), chi.URLParam(r, "name")))
}

func (s *Server) getDevice(w http.ResponseWriter, r *http.Request) {
	d, err := s.store.GetDevice(r.Context(), chi.URLParam(r, "name"))
	respondOne(w, d, err)
}

func (s *Server) deleteDevice(w http.ResponseWriter, r *http.Request) {
	respondDelete(w, s.store.DeleteDevice(r.Context(), chi.URLParam(r, "name")))
}

func (s *Server) getBinding(w http.ResponseWriter, r *http.Request) {
	b, err := s.store.GetBinding(r.Context(), chi.URLParam(r, "name"), chi.URLParam(r, "zone"))
	respondOne(w, b, err)
}

func (s *Server) deleteBinding(w http.ResponseWriter, r *http.Request) {
	respondDelete(w, s.store.DeleteBinding(r.Context(), chi.URLParam(r, "name"), chi.URLParam(r, "zone")))
}

func (s *Server) getRule(w http.ResponseWriter, r *http.Request) {
	id, err := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
	if err != nil {
		writeError(w, http.StatusBadRequest, "id must be an integer")
		return
	}
	rule, err := s.store.GetRule(r.Context(), id)
	respondOne(w, rule, err)
}

// ---- Agent endpoints -------------------------------------------------------

func (s *Server) handleDeviceConfig(w http.ResponseWriter, r *http.Request) {
	cfg, err := compiler.Compile(r.Context(), s.store, chi.URLParam(r, "name"))
	if err != nil {
		if errors.Is(err, store.ErrNotFound) {
			writeError(w, http.StatusNotFound, "device not found")
			return
		}
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	body, err := cfg.Marshal()
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	w.Header().Set("Content-Type", "application/yaml")
	w.Header().Set("X-Tomswall-Generation", strconv.FormatInt(cfg.Generation, 10))
	w.WriteHeader(http.StatusOK)
	_, _ = w.Write(body)
}

func (s *Server) handleDeviceStatus(w http.ResponseWriter, r *http.Request) {
	var body struct {
		Generation int64 `json:"generation"`
	}
	if !decode(w, r, &body) {
		return
	}
	if err := s.store.RecordDeviceStatus(r.Context(), chi.URLParam(r, "name"), body.Generation); err != nil {
		if errors.Is(err, store.ErrNotFound) {
			writeError(w, http.StatusNotFound, "device not found")
			return
		}
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

// ---- helpers ---------------------------------------------------------------

// decode reads a JSON request body into v, writing a 400 on failure. It returns
// false when the caller should stop.
func decode(w http.ResponseWriter, r *http.Request, v any) bool {
	dec := json.NewDecoder(r.Body)
	dec.DisallowUnknownFields()
	if err := dec.Decode(v); err != nil {
		writeError(w, http.StatusBadRequest, "invalid JSON: "+err.Error())
		return false
	}
	return true
}

// respondList writes a list result or a 500, normalizing a nil slice to [].
func respondList[T any](w http.ResponseWriter, list []T, err error) {
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	if list == nil {
		list = []T{}
	}
	writeJSON(w, http.StatusOK, list)
}