package ui

import (
	"context"
	"time"

	"git.stinnesbeck.com/nils/arr-tui/internal/sabnzbd"
	"github.com/rivo/tview"
)

// watchInterval is how often SABnzbd's history is checked for finished
// downloads in the background, whatever view is showing.
const watchInterval = 15 * time.Second

// downloadEvent is a download that just finished or failed.
type downloadEvent struct {
	name    string
	failed  bool
	message string // failure reason, if any
}

// diffHistory compares SABnzbd's history with what was seen before and
// returns the downloads that reached a final state since. seen maps job id to
// the last known status and is updated. With baseline set (the first poll) the
// current state is only recorded, so downloads that finished before arr-tui
// started do not produce notifications.
func diffHistory(seen map[string]string, slots []sabnzbd.HistorySlot, baseline bool) []downloadEvent {
	var events []downloadEvent
	for _, s := range slots {
		prev, known := seen[s.ID]
		seen[s.ID] = s.Status
		final := s.Status == "Completed" || s.Failed()
		if baseline || !final || (known && prev == s.Status) {
			continue
		}
		events = append(events, downloadEvent{name: s.Name, failed: s.Failed(), message: s.FailMessage})
	}
	return events
}

// watchDownloads polls SABnzbd's history until ctx ends and reports finished
// and failed downloads as popups (and a bell, if enabled). Errors are not
// reported here: the connection indicator and the log already do that.
func (a *App) watchDownloads(ctx context.Context, sab *sabnzbd.Client, bell bool) {
	seen := map[string]string{}
	baseline := true
	t := time.NewTicker(watchInterval)
	defer t.Stop()
	for {
		hctx, cancel := context.WithTimeout(ctx, 10*time.Second)
		slots, err := sab.History(hctx, 30)
		cancel()
		if err == nil {
			events := diffHistory(seen, slots, baseline)
			baseline = false
			if len(events) > 0 {
				a.post(func() { a.announce(events, bell) })
			}
		}
		select {
		case <-ctx.Done():
			return
		case <-t.C:
		}
	}
}

// announce shows a popup for each event; UI goroutine only.
func (a *App) announce(events []downloadEvent, bell bool) {
	for _, e := range events {
		if e.failed {
			text := "Download failed: " + tview.Escape(e.name)
			if e.message != "" {
				text += " (" + tview.Escape(truncate(e.message, 60)) + ")"
			}
			a.SetMessage("[red]" + text)
		} else {
			a.SetMessage("[green]Download finished: " + tview.Escape(e.name))
		}
	}
	if bell {
		if a.screen != nil {
			a.screen.Beep()
		}
	}
}