package processapi

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

	"github.com/itworx/pulse/internal/auth"
	"github.com/itworx/pulse/internal/problem"
	"github.com/itworx/pulse/internal/process"
)

type Handler struct {
	Provider interface {
		Snapshot(context.Context) (process.Snapshot, error)
	}
	Limits process.Limits
}

func (h Handler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet || r.URL.Path != "/api/v1/processes" {
		http.NotFound(w, r)
		return
	}
	if _, ok := auth.PrincipalFromContext(r.Context()); !ok {
		problem.Write(w, r, http.StatusUnauthorized, "UNAUTHORIZED", "Authentication required", "Authentication is required to read processes.", nil)
		return
	}
	limit := 50
	if value := r.URL.Query().Get("limit"); value != "" {
		parsed, err := strconv.Atoi(value)
		if err != nil {
			problem.Write(w, r, http.StatusBadRequest, "PROCESS_LIMIT_INVALID", "Invalid process limit", "The process page limit is invalid.", nil)
			return
		}
		limit = parsed
	}
	mode := process.SortMode(r.URL.Query().Get("sort"))
	if mode == "" {
		mode = process.SortCPU
	}
	var snapshot process.Snapshot
	var err error
	if h.Provider == nil {
		snapshot = process.UnknownSnapshot(time.Now().UTC(), "process", "agent", "source_unavailable")
	} else {
		snapshot, err = h.Provider.Snapshot(r.Context())
	}
	if err != nil {
		if errors.Is(err, context.Canceled) || errors.Is(err, context.DeadlineExceeded) {
			return
		}
		problem.Write(w, r, http.StatusServiceUnavailable, "PROCESS_UNAVAILABLE", "Processgegevens niet beschikbaar", "De procesgegevens konden niet worden gelezen.", nil)
		return
	}
	page, err := process.FilteredPage(snapshot, mode, limit, r.URL.Query().Get("after"), h.Limits, r.URL.Query().Get("q"), r.URL.Query().Get("container"))
	if err != nil {
		problem.Write(w, r, http.StatusBadRequest, "PROCESS_QUERY_INVALID", "Invalid process query", "The process sort, cursor or limit is invalid.", nil)
		return
	}
	w.Header().Set("Content-Type", "application/json")
	w.Header().Set("Cache-Control", "private, max-age=5")
	_ = json.NewEncoder(w).Encode(page)
}