// Package handler contains HTTP handlers for the Control Center API.
// Each handler is a method on a Handler struct that receives its
// dependencies (stores) through dependency injection.
package handler

import (
	"encoding/json"
	"net/http"
	"time"

	"code.cubecraftcreations.com/CubeCraft-Creations/Control-Center/go-backend/internal/models"
	"code.cubecraftcreations.com/CubeCraft-Creations/Control-Center/go-backend/internal/store"
	"github.com/go-chi/chi/v5"
	"github.com/go-playground/validator/v10"
)

// Handler groups all route handlers and their dependencies.
type Handler struct {
	AgentStore   *store.AgentStore
	SessionStore *store.SessionStore
	TaskStore    *store.TaskStore
	ProjectStore *store.ProjectStore
	validate     *validator.Validate
}

// NewHandler returns a fully wired Handler.
func NewHandler(
	as *store.AgentStore,
	ss *store.SessionStore,
	ts *store.TaskStore,
	ps *store.ProjectStore,
) *Handler {
	v := validator.New()
	v.RegisterValidation("agentStatus", validateAgentStatus)
	return &Handler{
		AgentStore:   as,
		SessionStore: ss,
		TaskStore:    ts,
		ProjectStore: ps,
		validate:     v,
	}
}

// ─── Agent Handlers ────────────────────────────────────────────────────────────

// ListAgents handles GET /api/agents.
func (h *Handler) ListAgents(w http.ResponseWriter, r *http.Request) {
	statusFilter := models.AgentStatus(r.URL.Query().Get("status"))
	allAgents := h.AgentStore.List(statusFilter)

	page, pageSize := parsePagination(r)
	start, end := paginateSlice(len(allAgents), page, pageSize)

	pageSlice := allAgents[start:end]
	writeJSON(w, http.StatusOK, models.PaginatedResponse{
		Data:       pageSlice,
		TotalCount: h.AgentStore.Count(),
		Page:       page,
		PageSize:   pageSize,
		HasMore:    end < len(allAgents),
	})
}

// GetAgent handles GET /api/agents/{id}.
func (h *Handler) GetAgent(w http.ResponseWriter, r *http.Request) {
	id := chi.URLParam(r, "id")
	agent, ok := h.AgentStore.Get(id)
	if !ok {
		writeJSON(w, http.StatusNotFound, models.ErrorResponse{Error: "agent not found"})
		return
	}
	writeJSON(w, http.StatusOK, agent)
}

// CreateAgent handles POST /api/agents.
func (h *Handler) CreateAgent(w http.ResponseWriter, r *http.Request) {
	var req models.CreateAgentRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeJSON(w, http.StatusBadRequest, models.ErrorResponse{Error: "invalid request body"})
		return
	}

	if err := h.validate.Struct(req); err != nil {
		writeJSON(w, http.StatusUnprocessableEntity, models.ErrorResponse{
			Error:   "validation failed",
			Details: validationErrors(err),
		})
		return
	}

	agent := models.AgentCardData{
		ID:          req.ID,
		DisplayName: req.DisplayName,
		Role:        req.Role,
		Status:      req.Status,
		CurrentTask: req.CurrentTask,
		SessionKey:  req.SessionKey,
		Channel:     req.Channel,
		LastActivity: time.Now().UTC().Format(time.RFC3339),
	}

	if ok := h.AgentStore.Create(agent); !ok {
		writeJSON(w, http.StatusConflict, models.ErrorResponse{Error: "agent with this ID already exists"})
		return
	}
	writeJSON(w, http.StatusCreated, agent)
}

// UpdateAgent handles PUT /api/agents/{id}.
func (h *Handler) UpdateAgent(w http.ResponseWriter, r *http.Request) {
	id := chi.URLParam(r, "id")

	var req models.UpdateAgentRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeJSON(w, http.StatusBadRequest, models.ErrorResponse{Error: "invalid request body"})
		return
	}

	if err := h.validate.Struct(req); err != nil {
		writeJSON(w, http.StatusUnprocessableEntity, models.ErrorResponse{
			Error:   "validation failed",
			Details: validationErrors(err),
		})
		return
	}

	agent, ok := h.AgentStore.Update(id, req)
	if !ok {
		writeJSON(w, http.StatusNotFound, models.ErrorResponse{Error: "agent not found"})
		return
	}
	writeJSON(w, http.StatusOK, agent)
}

// DeleteAgent handles DELETE /api/agents/{id}.
func (h *Handler) DeleteAgent(w http.ResponseWriter, r *http.Request) {
	id := chi.URLParam(r, "id")
	if ok := h.AgentStore.Delete(id); !ok {
		writeJSON(w, http.StatusNotFound, models.ErrorResponse{Error: "agent not found"})
		return
	}
	w.WriteHeader(http.StatusNoContent)
}

// AgentHistory handles GET /api/agents/{id}/history.
func (h *Handler) AgentHistory(w http.ResponseWriter, r *http.Request) {
	id := chi.URLParam(r, "id")
	if _, ok := h.AgentStore.Get(id); !ok {
		writeJSON(w, http.StatusNotFound, models.ErrorResponse{Error: "agent not found"})
		return
	}

	history := h.AgentStore.History(id)
	if history == nil {
		history = []models.AgentStatusHistoryEntry{}
	}
	writeJSON(w, http.StatusOK, history)
}