package http

import (
	"context"
	"encoding/json"
	"errors"
	"log/slog"
	stdhttp "net/http"
	"strconv"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgxpool"

	"github.com/nomadcode/nomadcode-core/internal/workflow"
)

type Handler struct {
	db       *pgxpool.Pool
	workflow *workflow.Service
	logger   *slog.Logger
}

func NewHandler(pool *pgxpool.Pool, workflowService *workflow.Service, logger *slog.Logger) *Handler {
	return &Handler{
		db:       pool,
		workflow: workflowService,
		logger:   logger,
	}
}

func (h *Handler) Healthz(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	writeJSON(w, stdhttp.StatusOK, map[string]string{"status": "ok"})
}

func (h *Handler) Readyz(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	ctx, cancel := context.WithTimeout(r.Context(), readyTimeout)
	defer cancel()

	if err := h.db.Ping(ctx); err != nil {
		writeError(w, stdhttp.StatusServiceUnavailable, "database is not ready")
		return
	}

	writeJSON(w, stdhttp.StatusOK, map[string]string{"status": "ready"})
}

func (h *Handler) CreateTask(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	var input workflow.CreateTaskInput
	if err := json.NewDecoder(r.Body).Decode(&input); err != nil {
		writeError(w, stdhttp.StatusBadRequest, "invalid JSON body")
		return
	}

	task, err := h.workflow.CreateTask(r.Context(), input)
	if err != nil {
		h.writeServiceError(w, err)
		return
	}

	writeJSON(w, stdhttp.StatusCreated, map[string]string{
		"id":     task.ID,
		"status": task.Status,
	})
}

func (h *Handler) GetTask(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	task, err := h.workflow.GetTask(r.Context(), chi.URLParam(r, "id"))
	if err != nil {
		h.writeServiceError(w, err)
		return
	}

	writeJSON(w, stdhttp.StatusOK, task)
}

func (h *Handler) ListTasks(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	limit := int32(20)
	if rawLimit := r.URL.Query().Get("limit"); rawLimit != "" {
		parsed, err := strconv.Atoi(rawLimit)
		if err != nil || parsed < 1 {
			writeError(w, stdhttp.StatusBadRequest, "limit must be a positive integer")
			return
		}
		limit = int32(parsed)
	}

	tasks, err := h.workflow.ListTasks(r.Context(), limit)
	if err != nil {
		h.writeServiceError(w, err)
		return
	}

	writeJSON(w, stdhttp.StatusOK, tasks)
}

func (h *Handler) EnqueueTask(w stdhttp.ResponseWriter, r *stdhttp.Request) {
	task, err := h.workflow.EnqueueTask(r.Context(), chi.URLParam(r, "id"))
	if err != nil {
		h.writeServiceError(w, err)
		return
	}

	writeJSON(w, stdhttp.StatusOK, map[string]string{
		"id":     task.ID,
		"status": task.Status,
	})
}

func (h *Handler) writeServiceError(w stdhttp.ResponseWriter, err error) {
	switch {
	case errors.Is(err, workflow.ErrInvalidTaskInput):
		writeError(w, stdhttp.StatusBadRequest, err.Error())
	case errors.Is(err, workflow.ErrTaskCannotBeEnqueued):
		writeError(w, stdhttp.StatusConflict, err.Error())
	case errors.Is(err, pgx.ErrNoRows):
		writeError(w, stdhttp.StatusNotFound, "task not found")
	default:
		if h.logger != nil {
			h.logger.Error("request failed", "error", err)
		}
		writeError(w, stdhttp.StatusInternalServerError, "internal server error")
	}
}

const readyTimeout = 2 * time.Second

func writeJSON(w stdhttp.ResponseWriter, status int, value any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	_ = json.NewEncoder(w).Encode(value)
}

func writeError(w stdhttp.ResponseWriter, status int, message string) {
	writeJSON(w, status, map[string]string{"error": message})
}