package incidentapi

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

	"github.com/itworx/pulse/internal/audit"
	"github.com/itworx/pulse/internal/auth"
	"github.com/itworx/pulse/internal/correlation"
	"github.com/itworx/pulse/internal/incident"
	"github.com/itworx/pulse/internal/problem"
)

type Handler struct {
	Store incident.Store
	Audit audit.Store
}

func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	principal, ok := auth.PrincipalFromContext(r.Context())
	if !ok {
		fail(w, r, http.StatusUnauthorized, "UNAUTHORIZED", "Authentication required.")
		return
	}
	path := strings.Trim(strings.TrimPrefix(r.URL.Path, "/api/v1/incidents"), "/")
	if path == "" && r.Method == http.MethodGet {
		h.list(w, r)
		return
	}
	parts := strings.Split(path, "/")
	if len(parts) == 1 && parts[0] != "" && r.Method == http.MethodPatch {
		if !auth.Allows(principal.Role, auth.PermissionOperate) {
			fail(w, r, http.StatusForbidden, "FORBIDDEN", "Incident ownership is not allowed for this role.")
			return
		}
		h.updateOwner(w, r, parts[0], principal.Subject)
		return
	}
	if len(parts) == 2 && parts[1] == "notes" && (r.Method == http.MethodGet || r.Method == http.MethodPost) {
		if r.Method == http.MethodPost && !auth.Allows(principal.Role, auth.PermissionOperate) {
			fail(w, r, http.StatusForbidden, "FORBIDDEN", "Incident notes are not allowed for this role.")
			return
		}
		if r.Method == http.MethodGet {
			h.listNotes(w, r, parts[0])
		} else {
			h.addNote(w, r, parts[0], principal.Subject)
		}
		return
	}
	if len(parts) == 1 && parts[0] != "" && r.Method == http.MethodGet {
		h.get(w, r, parts[0])
		return
	}
	if len(parts) == 3 && parts[1] == "alerts" && parts[2] != "" && (r.Method == http.MethodPost || r.Method == http.MethodDelete) {
		if !auth.Allows(principal.Role, auth.PermissionOperate) {
			fail(w, r, http.StatusForbidden, "FORBIDDEN", "Incident association is not allowed for this role.")
			return
		}
		if r.Method == http.MethodPost {
			h.associate(w, r, parts[0], parts[2], principal.Subject)
			return
		}
		h.disassociate(w, r, parts[0], parts[2], principal.Subject)
		return
	}
	fail(w, r, http.StatusNotFound, "NOT_FOUND", "Incident route not found.")
}

func (h Handler) list(w http.ResponseWriter, r *http.Request) {
	limit := 100
	if value := r.URL.Query().Get("limit"); value != "" {
		parsed, err := strconv.Atoi(value)
		if err != nil || parsed < 1 || parsed > 100 {
			fail(w, r, http.StatusBadRequest, "INVALID_LIMIT", "The incident limit must be between 1 and 100.")
			return
		}
		limit = parsed
	}
	status := incident.Status(r.URL.Query().Get("status"))
	items, err := h.Store.List(r.Context(), limit, status)
	if err != nil {
		h.repositoryFailure(w, r, err)
		return
	}
	write(w, http.StatusOK, map[string]any{"items": items})
}

func (h Handler) get(w http.ResponseWriter, r *http.Request, id string) {
	item, err := h.Store.Get(r.Context(), id)
	if err != nil {
		h.repositoryFailure(w, r, err)
		return
	}
	notes, notesErr := h.Store.ListNotes(r.Context(), id, 100)
	if notesErr != nil {
		h.repositoryFailure(w, r, notesErr)
		return
	}
	item.Notes = notes
	write(w, http.StatusOK, map[string]any{"incident": item})
}

func (h Handler) associate(w http.ResponseWriter, r *http.Request, incidentID, alertID, actor string) {
	var request struct {
		Rationale  string  `json:"rationale"`
		Confidence float64 `json:"confidence"`
	}
	if err := decode(r, &request); err != nil {
		fail(w, r, http.StatusBadRequest, "INVALID_ASSOCIATION", "The incident association document is invalid.")
		return
	}
	if request.Confidence == 0 {
		request.Confidence = 1
	}
	item, duplicate, err := h.Store.AssociateAlert(r.Context(), incidentID, alertID, strings.TrimSpace(request.Rationale), request.Confidence, actor)
	if err != nil {
		h.repositoryFailure(w, r, err)
		return
	}
	if h.Audit != nil {
		result := "success"
		if duplicate {
			result = "idempotent"
		}
		if err := h.Audit.Append(r.Context(), audit.Event{Actor: actor, Action: "incident.alert.associate", ResourceType: "incident", ResourceID: incidentID, Result: result, CorrelationID: correlation.FromContext(r.Context()), After: map[string]any{"alertId": alertID, "rationale": request.Rationale, "confidence": request.Confidence, "manual": true, "duplicate": duplicate}}); err != nil {
			fail(w, r, http.StatusServiceUnavailable, "AUDIT_UNAVAILABLE", "The audit event could not be recorded.")
			return
		}
	}
	write(w, http.StatusOK, map[string]any{"association": item, "duplicate": duplicate})
}

func (h Handler) disassociate(w http.ResponseWriter, r *http.Request, incidentID, alertID, actor string) {
	if err := h.Store.DisassociateAlert(r.Context(), incidentID, alertID); err != nil {
		h.repositoryFailure(w, r, err)
		return
	}
	if h.Audit != nil {
		if err := h.Audit.Append(r.Context(), audit.Event{Actor: actor, Action: "incident.alert.disassociate", ResourceType: "incident", ResourceID: incidentID, Result: "success", CorrelationID: correlation.FromContext(r.Context()), After: map[string]any{"alertId": alertID, "manual": true}}); err != nil {
			fail(w, r, http.StatusServiceUnavailable, "AUDIT_UNAVAILABLE", "The audit event could not be recorded.")
			return
		}
	}
	w.WriteHeader(http.StatusNoContent)
}

func (h Handler) updateOwner(w http.ResponseWriter, r *http.Request, id, actor string) {
	var request struct {
		OwnerUserID string `json:"ownerUserId"`
		Revision    int64  `json:"revision"`
	}
	if err := decode(r, &request); err != nil || request.Revision < 1 {
		fail(w, r, http.StatusBadRequest, "INVALID_INCIDENT", "A valid owner and revision document is required.")
		return
	}
	item, err := h.Store.UpdateOwner(r.Context(), id, strings.TrimSpace(request.OwnerUserID), request.Revision)
	if err != nil {
		h.repositoryFailure(w, r, err)
		return
	}
	if h.Audit != nil {
		if err := h.Audit.Append(r.Context(), audit.Event{Actor: actor, Action: "incident.owner.update", ResourceType: "incident", ResourceID: id, Result: "success", CorrelationID: correlation.FromContext(r.Context()), After: map[string]any{"ownerUserId": request.OwnerUserID, "revision": item.Revision}}); err != nil {
			fail(w, r, http.StatusServiceUnavailable, "AUDIT_UNAVAILABLE", "The audit event could not be recorded.")
			return
		}
	}
	write(w, http.StatusOK, map[string]any{"incident": item})
}

func (h Handler) listNotes(w http.ResponseWriter, r *http.Request, id string) {
	items, err := h.Store.ListNotes(r.Context(), id, 100)
	if err != nil {
		h.repositoryFailure(w, r, err)
		return
	}
	write(w, http.StatusOK, map[string]any{"items": items})
}

func (h Handler) addNote(w http.ResponseWriter, r *http.Request, id, actor string) {
	var request struct {
		Body string `json:"body"`
	}
	if err := decode(r, &request); err != nil {
		fail(w, r, http.StatusBadRequest, "INVALID_NOTE", "The incident note is invalid.")
		return
	}
	note, err := h.Store.AddNote(r.Context(), id, actor, request.Body)
	if err != nil {
		h.repositoryFailure(w, r, err)
		return
	}
	if h.Audit != nil {
		if err := h.Audit.Append(r.Context(), audit.Event{Actor: actor, Action: "incident.note.create", ResourceType: "incident", ResourceID: id, Result: "success", CorrelationID: correlation.FromContext(r.Context()), After: map[string]any{"noteId": note.ID}}); err != nil {
			fail(w, r, http.StatusServiceUnavailable, "AUDIT_UNAVAILABLE", "The audit event could not be recorded.")
			return
		}
	}
	write(w, http.StatusCreated, map[string]any{"note": note})
}
func (h Handler) repositoryFailure(w http.ResponseWriter, r *http.Request, err error) {
	switch {
	case errors.Is(err, incident.ErrInvalid):
		fail(w, r, http.StatusBadRequest, "INVALID_INCIDENT", "The incident request is invalid.")
	case errors.Is(err, incident.ErrNotFound):
		fail(w, r, http.StatusNotFound, "NOT_FOUND", "The incident was not found.")
	case errors.Is(err, incident.ErrConflict):
		fail(w, r, http.StatusConflict, "CONFLICT", "The incident changed before this operation was applied.")
	case errors.Is(err, incident.ErrUnavailable):
		fail(w, r, http.StatusServiceUnavailable, "DATABASE_UNAVAILABLE", "Incidents are unavailable.")
	default:
		fail(w, r, http.StatusInternalServerError, "INCIDENT_REQUEST_FAILED", "The incident request failed.")
	}
}
func decode(r *http.Request, target any) error {
	body, err := io.ReadAll(io.LimitReader(r.Body, 1<<20+1))
	if err != nil {
		return err
	}
	defer r.Body.Close()
	if len(body) > 1<<20 {
		return errors.New("request too large")
	}
	decoder := json.NewDecoder(strings.NewReader(string(body)))
	decoder.DisallowUnknownFields()
	if err := decoder.Decode(target); err != nil {
		return err
	}
	var extra any
	if err := decoder.Decode(&extra); err != io.EOF {
		return errors.New("multiple JSON values")
	}
	return nil
}
func fail(w http.ResponseWriter, r *http.Request, status int, code, detail string) {
	problem.Write(w, r, status, code, http.StatusText(status), detail, nil)
}
func write(w http.ResponseWriter, status int, value any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(value)
}