package notifications

import (
	"encoding/json"
	"fmt"
	"strings"

	"git.fabledsword.com/bvandeusen/minstrel/internal/words"
)

// 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"`
	// Artist and Title are Name's parts, for request_completed: the new-music
	// summary email groups arrivals by artist. Title is empty for an artist
	// request.
	Artist   string `json:"artist,omitempty"`
	Title    string `json:"title,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 since the notice was last
	// read.
	Count int64 `json:"count,omitempty"`
	// Items name what Count counts, one each, newest first: "Weezer – Buddy
	// Holly". A coalesced update puts its own in front and keeps ten (M542),
	// so the body can say which, not only how many.
	Items []string `json:"items,omitempty"`
	// Detail is free text: scan_failed's error message. Rows from before
	// Items also carry duplicates_resolved's summary here.
	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: "/collection/reports"}
	case KindScanFailed:
		title := "Library scan failed"
		if p.Count > 1 {
			title = fmt.Sprintf("Library scan failed %d times", p.Count)
		}
		body := "The last scan stopped with an error."
		if p.Detail != "" {
			body = "The last scan stopped: " + p.Detail
		}
		return Rendered{Title: title, Body: body, Link: "/admin/library"}
	case KindTracksMissing:
		body := "Their files are no longer where the library expects them."
		if names := nameList(p.Items, p.Count); names != "" {
			body = "No longer on disk: " + names + "."
		}
		return Rendered{
			Title: plural(p.Count, "track went missing", "tracks went missing"),
			Body:  body,
			Link:  "/collection/missing",
		}
	case KindDuplicatesFound:
		body := "The duplicate sweep found tracks holding the same recording."
		if names := nameList(p.Items, p.Count); names != "" {
			body = "Held more than once: " + names + "."
		}
		return Rendered{
			Title: plural(p.Count, "new duplicate to review", "new duplicates to review"),
			Body:  body,
			Link:  "/collection/duplicates",
		}
	case KindDuplicatesResolved:
		body := "Extra copies of a song were merged into the one the album keeps."
		switch names := nameList(p.Items, p.Count); {
		case names != "":
			body = "Extra copies removed, the right one kept: " + names + "."
		case p.Detail != "":
			body = p.Detail
		}
		return Rendered{
			Title: plural(p.Count, "duplicate merged automatically", "duplicates merged automatically"),
			Body:  body,
			Link:  "/collection/duplicates?view=resolved",
		}
	case KindPlaybackErrors:
		body := "A track failed to play for someone."
		if names := nameList(p.Items, p.Count); names != "" {
			body = "Failed to play: " + names + "."
		}
		return Rendered{
			Title: plural(p.Count, "playback error reported", "playback errors reported"),
			Body:  body,
			Link:  "/collection/reports",
		}
	default:
		return Rendered{Title: "Notification", Link: "/"}
	}
}

// namesShown is how many of a notice's items its body names.
const namesShown = 3

// nameList names the first few items, then how many more of the total there
// are: "A, B, C and 4 more". Empty when there are no items.
func nameList(items []string, total int64) string {
	if len(items) == 0 {
		return ""
	}
	shown := items[:min(len(items), namesShown)]
	more := max(total, int64(len(items))) - int64(len(shown))
	if more > 0 {
		return strings.Join(shown, ", ") + " and " + words.Count(more, "more", "more")
	}
	if len(shown) == 1 {
		return shown[0]
	}
	return strings.Join(shown[:len(shown)-1], ", ") + " and " + shown[len(shown)-1]
}

func plural(n int64, one, many string) string {
	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 words.Count(n, one, many)
}