package api

import (
	"net/http"
	"strings"
	"time"

	"github.com/ponzischeme89/memby/server/internal/store"
)

// The console's window on the outbound notification log.
//
// One route rather than three, unlike the sign-in history: an operator arrives here with a
// *question* — "did the weekly summary go out", "why did nobody get told about that
// import" — and every part of the answer is the same filtered window. Splitting the table
// from its totals would mean two requests that could disagree with each other while a
// filter was being typed.
const (
	// notificationPageLimit caps one page. Large enough that the ordinary answer needs no
	// paging, small enough that a household with a busy week does not send a megabyte.
	notificationPageLimit = 100
	// notificationWindowDays is the widest window the page offers, derived from the
	// retention period rather than written down: PruneNotificationLog removes anything
	// older, so a page offering 180 days would draw a flat line for half of it.
	notificationWindowDays = int(store.NotificationRetention / (24 * time.Hour))
)

type adminNotificationLogResponse struct {
	Entries   []store.NotificationLogEntry `json:"entries"`
	Total     int                          `json:"total"`
	Limit     int                          `json:"limit"`
	Offset    int                          `json:"offset"`
	Totals    store.NotificationLogTotals  `json:"totals"`
	Days      []store.NotificationLogDay   `json:"days"`
	Facets    store.NotificationFacets     `json:"facets"`
	Users     []store.KnownUser            `json:"users"`
	Retention int                          `json:"retentionDays"`
}

// notificationLogFilter reads the console's question off the query string.
//
// Every list filter is comma-separated and multi-valued, because the useful questions are
// plural: "everything that failed or was skipped", "both digest kinds". A single-valued
// filter would make the common troubleshooting question take two passes.
func notificationLogFilter(r *http.Request) store.NotificationLogFilter {
	query := r.URL.Query()
	filter := store.NotificationLogFilter{
		UserID:   strings.TrimSpace(query.Get("user")),
		Kinds:    splitCSV(query.Get("kind")),
		Channels: splitCSV(query.Get("channel")),
		Statuses: splitCSV(query.Get("status")),
		Sources:  splitCSV(query.Get("source")),
		Query:    strings.TrimSpace(query.Get("q")),
		Limit:    queryInt(r, "limit", notificationPageLimit, 500),
		Offset:   queryInt(r, "offset", 0, 100000),
	}
	filter.From, filter.To = notificationWindow(r)
	return filter
}

// notificationWindow resolves the date range.
//
// An explicit `from` wins over the day window, the rule the sign-in history follows: an
// operator who typed a date meant it, and silently narrowing it to the last week would
// answer a question they did not ask. `to` is read as the *end* of the day named, because
// somebody filtering "to the 12th" means through the 12th, not up to midnight at its start.
func notificationWindow(r *http.Request) (time.Time, time.Time) {
	query := r.URL.Query()
	from := parseDay(query.Get("from"))
	to := parseDay(query.Get("to"))
	if !to.IsZero() {
		to = to.AddDate(0, 0, 1)
	}
	if from.IsZero() {
		days := queryInt(r, "days", 7, notificationWindowDays)
		if days > 0 {
			from = time.Now().UTC().AddDate(0, 0, -days)
		}
	}
	return from, to
}

func parseDay(raw string) time.Time {
	raw = strings.TrimSpace(raw)
	if raw == "" {
		return time.Time{}
	}
	day, err := time.Parse("2006-01-02", raw)
	if err != nil {
		return time.Time{}
	}
	return day
}

// handleAdminNotificationLog answers the Notifications page.
//
// The log is the page and everything else is decoration, which is why only its failure is
// a 500: a facet list or a name lookup that will not answer costs a dropdown, and an
// operator reading this page after something went wrong must still get the rows.
func (s *Server) handleAdminNotificationLog(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()
	filter := notificationLogFilter(r)

	page, err := s.store.NotificationLog(ctx, filter)
	if err != nil {
		s.loggerFor(ctx).Error("notification log read failed", "error", err)
		writeError(w, http.StatusInternalServerError, "could not read the notification history")
		return
	}

	response := adminNotificationLogResponse{
		Entries: page.Entries, Total: page.Total, Limit: page.Limit, Offset: page.Offset,
		Days: []store.NotificationLogDay{}, Users: []store.KnownUser{},
		Retention: notificationWindowDays,
	}
	if totals, err := s.store.NotificationLogTotals(ctx, filter); err == nil {
		response.Totals = totals
	} else {
		s.loggerFor(ctx).Warn("notification totals unavailable", "error", err)
	}
	if days, err := s.store.NotificationLogDays(ctx, filter); err == nil {
		response.Days = days
	}
	// Facets are computed over the whole retention window rather than the current filter,
	// so narrowing the table never removes the option that would widen it again.
	since := time.Now().UTC().Add(-store.NotificationRetention)
	if facets, err := s.store.NotificationLogFacets(ctx, since); err == nil {
		response.Facets = facets
	} else {
		s.loggerFor(ctx).Warn("notification facets unavailable", "error", err)
	}
	if users, err := s.store.KnownUsers(ctx); err == nil {
		response.Users = users
	}

	w.Header().Set("Cache-Control", "no-store")
	writeJSON(w, http.StatusOK, response)
}