package api

import (
	"net/http"
	"strconv"
	"strings"

	"github.com/snip/backend/internal/domain"
	"github.com/snip/backend/internal/service"
)

// /api/v1/links  — POST create (auth optional), GET list (auth required)
func (a *API) linksCollection(w http.ResponseWriter, r *http.Request) {
	switch r.Method {
	case http.MethodPost:
		a.createLink(w, r)
	case http.MethodGet:
		a.listLinks(w, r)
	default:
		w.WriteHeader(http.StatusMethodNotAllowed)
	}
}

func (a *API) createLink(w http.ResponseWriter, r *http.Request) {
	var req createReq
	if err := decode(r, &req); err != nil {
		writeError(w, domain.ErrInvalidURL)
		return
	}
	mode := domain.Mode(req.Mode)
	if mode != domain.ModeRandom && mode != domain.ModeMemorable && mode != domain.ModeCustom {
		mode = domain.ModeRandom
	}
	link, err := a.links.Create(r.Context(), service.CreateInput{
		LongURL:     req.LongURL,
		Mode:        mode,
		CustomAlias: req.CustomAlias,
		Pin:         req.Pin,
	}, a.userID(r))
	if err != nil {
		writeError(w, err)
		return
	}
	writeJSON(w, http.StatusCreated, toDTO(link))
}

func (a *API) listLinks(w http.ResponseWriter, r *http.Request) {
	q := r.URL.Query()
	page, _ := strconv.Atoi(q.Get("page"))
	pageSize, _ := strconv.Atoi(q.Get("pageSize"))

	result, err := a.links.List(r.Context(), a.userID(r), q.Get("q"), page, pageSize)
	if err != nil {
		writeError(w, err)
		return
	}
	items := make([]linkDTO, 0, len(result.Items))
	for i := range result.Items {
		items = append(items, toDTO(&result.Items[i]))
	}
	writeJSON(w, http.StatusOK, listResponse{
		Items:    items,
		Total:    result.Total,
		Page:     result.Page,
		PageSize: result.PageSize,
	})
}

func (a *API) linkStats(w http.ResponseWriter, r *http.Request) {
	stats, err := a.links.Stats(r.Context(), a.userID(r))
	if err != nil {
		writeError(w, err)
		return
	}
	writeJSON(w, http.StatusOK, stats)
}

// /api/v1/links/{id}        — PATCH, DELETE
// /api/v1/links/{id}/pin    — PUT, DELETE
func (a *API) linkItem(w http.ResponseWriter, r *http.Request) {
	rest := pathTail(r.URL.Path, "/api/v1/links/")
	parts := strings.Split(strings.Trim(rest, "/"), "/")
	id := parts[0]
	if id == "" {
		w.WriteHeader(http.StatusNotFound)
		return
	}
	owner := a.userID(r)

	// /{id}/pin
	if len(parts) == 2 && parts[1] == "pin" {
		a.managePin(w, r, id, owner)
		return
	}
	if len(parts) != 1 {
		w.WriteHeader(http.StatusNotFound)
		return
	}

	switch r.Method {
	case http.MethodPatch:
		var req updateReq
		if err := decode(r, &req); err != nil {
			writeError(w, domain.ErrInvalidURL)
			return
		}
		link, err := a.links.UpdateDestination(r.Context(), id, owner, req.LongURL)
		if err != nil {
			writeError(w, err)
			return
		}
		writeJSON(w, http.StatusOK, toDTO(link))
	case http.MethodDelete:
		if err := a.links.Delete(r.Context(), id, owner); err != nil {
			writeError(w, err)
			return
		}
		w.WriteHeader(http.StatusNoContent)
	default:
		w.WriteHeader(http.StatusMethodNotAllowed)
	}
}

func (a *API) managePin(w http.ResponseWriter, r *http.Request, id, owner string) {
	switch r.Method {
	case http.MethodPut:
		var req pinReq
		if err := decode(r, &req); err != nil {
			writeError(w, domain.ErrInvalidPin)
			return
		}
		link, err := a.links.SetPin(r.Context(), id, owner, req.Pin)
		if err != nil {
			writeError(w, err)
			return
		}
		writeJSON(w, http.StatusOK, toDTO(link))
	case http.MethodDelete:
		link, err := a.links.SetPin(r.Context(), id, owner, "")
		if err != nil {
			writeError(w, err)
			return
		}
		writeJSON(w, http.StatusOK, toDTO(link))
	default:
		w.WriteHeader(http.StatusMethodNotAllowed)
	}
}