package api

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

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

	"geniusrun/backend/internal/classify"
	"geniusrun/backend/internal/store"
)

// workoutKindResponse combines a workout kind's rule/metadata with its pace
// and HR range (stored separately in workout_type_paces), since the frontend
// always edits and displays them together.
type workoutKindResponse struct {
	store.WorkoutKind
	PaceMinSecPerKm *float64 `json:"pace_min_sec_per_km"`
	PaceMaxSecPerKm *float64 `json:"pace_max_sec_per_km"`
	HRMinPctHRR     *float64 `json:"hr_min_pct_hrr"`
	HRMaxPctHRR     *float64 `json:"hr_max_pct_hrr"`
}

func (s *Server) toWorkoutKindResponse(r *http.Request, k store.WorkoutKind) (workoutKindResponse, error) {
	userID := userIDFromContext(r.Context())
	pace, err := s.DB.GetWorkoutTypePace(r.Context(), userID, k.ID)
	if err != nil {
		return workoutKindResponse{}, err
	}
	return workoutKindResponse{
		WorkoutKind:     k,
		PaceMinSecPerKm: pace.PaceMinSecPerKm,
		PaceMaxSecPerKm: pace.PaceMaxSecPerKm,
		HRMinPctHRR:     pace.HRMinPctHRR,
		HRMaxPctHRR:     pace.HRMaxPctHRR,
	}, nil
}

type workoutKindRequest struct {
	Name            string          `json:"name"`
	Description     string          `json:"description"`
	Color           string          `json:"color"`
	Rule            json.RawMessage `json:"rule"`
	Priority        int             `json:"priority"`
	IsActive        *bool           `json:"is_active"`
	PaceMinSecPerKm *float64        `json:"pace_min_sec_per_km"`
	PaceMaxSecPerKm *float64        `json:"pace_max_sec_per_km"`
	HRMinPctHRR     *float64        `json:"hr_min_pct_hrr"`
	HRMaxPctHRR     *float64        `json:"hr_max_pct_hrr"`
}

func (req workoutKindRequest) validate() (classify.Node, error) {
	var node classify.Node
	if req.Name == "" {
		return node, errors.New("name is required")
	}
	if err := json.Unmarshal(req.Rule, &node); err != nil {
		return node, errors.New("rule is not valid JSON: " + err.Error())
	}
	if err := node.Validate(); err != nil {
		return node, errors.New("invalid rule: " + err.Error())
	}
	if req.PaceMinSecPerKm != nil && req.PaceMaxSecPerKm != nil && *req.PaceMinSecPerKm >= *req.PaceMaxSecPerKm {
		return node, errors.New("pace_min_sec_per_km must be less than pace_max_sec_per_km")
	}
	if req.HRMinPctHRR != nil && req.HRMaxPctHRR != nil && *req.HRMinPctHRR >= *req.HRMaxPctHRR {
		return node, errors.New("hr_min_pct_hrr must be less than hr_max_pct_hrr")
	}
	return node, nil
}

func (s *Server) handleListWorkoutKinds(w http.ResponseWriter, r *http.Request) {
	userID := userIDFromContext(r.Context())
	activeOnly := r.URL.Query().Get("include_inactive") != "true"
	kinds, err := s.DB.ListWorkoutKinds(r.Context(), userID, activeOnly)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	resp := make([]workoutKindResponse, 0, len(kinds))
	for _, k := range kinds {
		wr, err := s.toWorkoutKindResponse(r, k)
		if err != nil {
			writeError(w, http.StatusInternalServerError, err.Error())
			return
		}
		resp = append(resp, wr)
	}
	writeJSON(w, http.StatusOK, resp)
}

func (s *Server) handleGetWorkoutKind(w http.ResponseWriter, r *http.Request) {
	userID := userIDFromContext(r.Context())
	id, err := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid workout kind id")
		return
	}
	kind, ok, err := s.DB.GetWorkoutKind(r.Context(), userID, id)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	if !ok {
		writeError(w, http.StatusNotFound, "workout kind not found")
		return
	}
	resp, err := s.toWorkoutKindResponse(r, kind)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, resp)
}

func (s *Server) handleUpdateWorkoutKind(w http.ResponseWriter, r *http.Request) {
	userID := userIDFromContext(r.Context())
	id, err := strconv.ParseInt(chi.URLParam(r, "id"), 10, 64)
	if err != nil {
		writeError(w, http.StatusBadRequest, "invalid workout kind id")
		return
	}
	existing, ok, err := s.DB.GetWorkoutKind(r.Context(), userID, id)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	if !ok {
		writeError(w, http.StatusNotFound, "workout kind not found")
		return
	}

	var req workoutKindRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}
	if _, err := req.validate(); err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}

	isActive := existing.IsActive
	if req.IsActive != nil {
		isActive = *req.IsActive
	}

	if err := s.DB.UpdateWorkoutKind(r.Context(), userID, store.WorkoutKind{
		ID: id, Name: req.Name, Description: req.Description, Color: req.Color,
		RuleJSON: string(req.Rule), Priority: req.Priority, IsActive: isActive,
	}); err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	if err := s.DB.UpdateWorkoutTypePace(r.Context(), userID, store.WorkoutTypePace{
		WorkoutKindID:   id,
		PaceMinSecPerKm: req.PaceMinSecPerKm,
		PaceMaxSecPerKm: req.PaceMaxSecPerKm,
		HRMinPctHRR:     req.HRMinPctHRR,
		HRMaxPctHRR:     req.HRMaxPctHRR,
	}); err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}

	kind, _, _ := s.DB.GetWorkoutKind(r.Context(), userID, id)
	resp, err := s.toWorkoutKindResponse(r, kind)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, resp)
}