package api

import (
	"database/sql"
	"net/http"
	"strings"

	"training-tracker/internal/models"
)

type SessionHandler struct {
	repo SessionRepository
}

func NewSessionHandler(repo SessionRepository) *SessionHandler {
	return &SessionHandler{repo: repo}
}

func (h *SessionHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	path := strings.TrimPrefix(r.URL.Path, "/api/sessions")
	path = strings.TrimPrefix(path, "/")
	parts := strings.Split(path, "/")

	if len(parts) >= 2 && parts[1] == "entries" {
		id, err := parseID(r, "/api/sessions/")
		if err != nil || id == 0 {
			respondError(w, http.StatusBadRequest, "session ID required")
			return
		}
		if r.Method == http.MethodPost {
			h.addEntry(w, r, id)
		} else {
			respondError(w, http.StatusMethodNotAllowed, "method not allowed")
		}
		return
	}

	id, _ := parseID(r, "/api/sessions/")

	switch r.Method {
	case http.MethodGet:
		if id > 0 {
			h.getByID(w, r, id)
		} else {
			h.list(w, r)
		}
	case http.MethodPost:
		h.create(w, r)
	case http.MethodPut:
		if id > 0 {
			h.update(w, r, id)
		} else {
			respondError(w, http.StatusBadRequest, "session ID required")
		}
	case http.MethodDelete:
		if id > 0 {
			h.delete(w, r, id)
		} else {
			respondError(w, http.StatusBadRequest, "session ID required")
		}
	default:
		respondError(w, http.StatusMethodNotAllowed, "method not allowed")
	}
}

func (h *SessionHandler) list(w http.ResponseWriter, r *http.Request) {
	sessions, err := h.repo.List(r.Context())
	if err != nil {
		respondError(w, http.StatusInternalServerError, "failed to list sessions")
		return
	}
	if sessions == nil {
		sessions = []models.Session{}
	}
	respondJSON(w, http.StatusOK, sessions)
}

func (h *SessionHandler) getByID(w http.ResponseWriter, r *http.Request, id int64) {
	session, err := h.repo.GetByID(r.Context(), id)
	if err != nil {
		respondError(w, http.StatusInternalServerError, "failed to get session")
		return
	}
	if session == nil {
		respondError(w, http.StatusNotFound, "session not found")
		return
	}
	respondJSON(w, http.StatusOK, session)
}

func (h *SessionHandler) create(w http.ResponseWriter, r *http.Request) {
	var req models.CreateSessionRequest
	if err := decodeJSON(r, &req); err != nil {
		respondError(w, http.StatusBadRequest, "invalid request body")
		return
	}

	if req.Date.IsZero() {
		respondError(w, http.StatusBadRequest, "date is required")
		return
	}

	session, err := h.repo.Create(r.Context(), &req)
	if err != nil {
		respondError(w, http.StatusInternalServerError, "failed to create session")
		return
	}
	respondJSON(w, http.StatusCreated, session)
}

func (h *SessionHandler) update(w http.ResponseWriter, r *http.Request, id int64) {
	var req models.CreateSessionRequest
	if err := decodeJSON(r, &req); err != nil {
		respondError(w, http.StatusBadRequest, "invalid request body")
		return
	}

	if req.Date.IsZero() {
		respondError(w, http.StatusBadRequest, "date is required")
		return
	}

	session, err := h.repo.Update(r.Context(), id, &req)
	if err != nil {
		respondError(w, http.StatusInternalServerError, "failed to update session")
		return
	}
	if session == nil {
		respondError(w, http.StatusNotFound, "session not found")
		return
	}
	respondJSON(w, http.StatusOK, session)
}

func (h *SessionHandler) delete(w http.ResponseWriter, r *http.Request, id int64) {
	err := h.repo.Delete(r.Context(), id)
	if err == sql.ErrNoRows {
		respondError(w, http.StatusNotFound, "session not found")
		return
	}
	if err != nil {
		respondError(w, http.StatusInternalServerError, "failed to delete session")
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

func (h *SessionHandler) addEntry(w http.ResponseWriter, r *http.Request, sessionID int64) {
	var req models.CreateSessionEntryRequest
	if err := decodeJSON(r, &req); err != nil {
		respondError(w, http.StatusBadRequest, "invalid request body")
		return
	}

	if req.ExerciseID == 0 {
		respondError(w, http.StatusBadRequest, "exercise_id is required")
		return
	}

	entry, err := h.repo.AddEntry(r.Context(), sessionID, &req)
	if err != nil {
		respondError(w, http.StatusInternalServerError, "failed to add session entry")
		return
	}
	respondJSON(w, http.StatusCreated, entry)
}