package notifications

import (
	"encoding/json"
	"fmt"
)

// Rendered is a notification as people read it. The server renders it once,
// so the web inbox, the Android inbox, the phone's shade and the email digest
// all say the same thing, and a wording change is one edit here rather than
// a phrase table per client.
type Rendered struct {
	Title string `json:"title"`
	Body  string `json:"body"`
	// Link is the web path the notification opens. Android maps the same
	// paths onto its screens.
	Link string `json:"link"`
}

// Payload is what producers put in a notification. Every field is optional;
// each kind documents the ones it uses in Render.
type Payload struct {
	RequestID   string `json:"request_id,omitempty"`
	RequestKind string `json:"request_kind,omitempty"` // artist | album | track
	// Name is what was requested or flagged, as the user would say it:
	// "WWW", "Moe Shop", "Moe Shop – WWW".
	Name     string `json:"name,omitempty"`
	ArtistID string `json:"artist_id,omitempty"`
	AlbumID  string `json:"album_id,omitempty"`
	// Actor is the other person involved: who asked, who flagged.
	Actor  string `json:"actor,omitempty"`
	Reason string `json:"reason,omitempty"`
	// Count is the coalesced kinds' running total.
	Count int64 `json:"count,omitempty"`
	// Detail is free text for scan_failed (the error message).
	Detail string `json:"detail,omitempty"`
}

// Map turns a Payload into the map Notify takes, dropping empty fields.
func (p Payload) Map() map[string]any {
	b, _ := json.Marshal(p)
	var m map[string]any
	_ = json.Unmarshal(b, &m)
	return m
}

// Render turns a stored row into what people read. An unreadable payload
// still renders, from the kind alone, rather than failing the whole inbox.
func Render(kind Kind, payload []byte) Rendered {
	var p Payload
	_ = json.Unmarshal(payload, &p)
	name := p.Name
	if name == "" {
		name = "Your request"
	}

	switch kind {
	case KindRequestApproved:
		return Rendered{Title: "Request approved", Body: name + " is on its way.", Link: "/requests"}
	case KindRequestRejected:
		body := name + " was declined."
		if p.Reason != "" {
			body = name + " was declined: " + p.Reason
		}
		return Rendered{Title: "Request declined", Body: body, Link: "/requests"}
	case KindRequestCompleted:
		link := "/requests"
		switch {
		case p.AlbumID != "":
			link = "/albums/" + p.AlbumID
		case p.ArtistID != "":
			link = "/artists/" + p.ArtistID
		}
		return Rendered{Title: "Now in your library", Body: name + " has arrived.", Link: link}
	case KindRequestPending:
		who := p.Actor
		if who == "" {
			who = "Someone"
		}
		return Rendered{Title: "Request to review", Body: who + " asked for " + name + ".", Link: "/admin/requests"}
	case KindQuarantineFlagged:
		who := p.Actor
		if who == "" {
			who = "Someone"
		}
		body := who + " flagged " + name + "."
		if p.Reason != "" {
			body = who + " flagged " + name + ": " + p.Reason
		}
		return Rendered{Title: "Track flagged", Body: body, Link: "/admin/quarantine"}
	case KindScanFailed:
		title := "Library scan failed"
		if p.Count > 1 {
			title = fmt.Sprintf("Library scan failed %d times", p.Count)
		}
		body := p.Detail
		if body == "" {
			body = "The last scan stopped with an error."
		}
		return Rendered{Title: title, Body: body, Link: "/admin"}
	case KindTracksMissing:
		return Rendered{
			Title: plural(p.Count, "track went missing", "tracks went missing"),
			Body:  "Their files are no longer where the library expects them.",
			Link:  "/admin/missing-files",
		}
	case KindDuplicatesFound:
		return Rendered{
			Title: plural(p.Count, "duplicate group to review", "duplicate groups to review"),
			Body:  "The duplicate sweep found tracks holding the same recording.",
			Link:  "/admin/duplicates",
		}
	case KindPlaybackErrors:
		return Rendered{
			Title: plural(p.Count, "playback error reported", "playback errors reported"),
			Body:  "A track failed to play for someone.",
			Link:  "/admin/playback-errors",
		}
	default:
		return Rendered{Title: "Notification", Link: "/"}
	}
}

func plural(n int64, one, many string) string {
	if n == 1 {
		return "1 " + one
	}
	if n < 1 {
		// A coalesced kind always carries a count; this only guards a
		// malformed row from reading "0 tracks went missing".
		return "Some " + many
	}
	return fmt.Sprintf("%d %s", n, many)
}