package fa

import (
	"context"
	"fmt"
	"iter"
	"time"

	"github.com/PuerkitoBio/goquery"

	"git.anthrove.art/public/go-fa-api/internal/urls"
)

// NoteID identifies a private message (note) thread on FA.
type NoteID int64

// NotePreview is a row from the notes inbox listing at /msg/pms/. It carries
// just enough to identify the thread and decide whether to fetch the full
// note via [Client.GetNote].
type NotePreview struct {
	ID        NoteID
	Subject   string
	Sender    UserRef // from-user as it appears in the inbox list
	SentAt    time.Time
	Unread    bool
	ThreadURL string // the /msg/pms/1/{id}/#message link FA renders
}

// Note is a single private message thread, as rendered at /viewmessage/{id}/.
// Subject and Body are the headline note; FA shows quoted prior replies
// inline within Body rather than as a separate thread, so callers wanting
// to programmatically split a conversation will need to walk Body's HTML.
type Note struct {
	ID       NoteID
	Subject  string
	From     UserRef
	To       UserRef
	SentAt   time.Time
	BodyHTML string
	BodyText string
}

// Notes iterates the private-message inbox at /msg/pms/. Each yielded
// [*NotePreview] is one thread; call [Client.GetNote] with its ID to load
// the body.
//
// FA paginates /msg/pms/ with a similar messagecenter-navigation control
// to the submission inbox.
//
// ListOptions.StartPage is ignored the inbox uses cursor pagination
// (follow-the-Next-link), not page-numbered fetches.
//
// Requires a logged-in client.
func (c *Client) Notes(ctx context.Context, opts ListOptions, reqOpts ...Option) iter.Seq2[*NotePreview, error] {
	return func(yield func(*NotePreview, error) bool) {
		nextURL := urls.MsgPMs()
		pagesFetched := 0
		for nextURL != "" {
			if opts.reachedLimit(pagesFetched) {
				return
			}
			var (
				items []*NotePreview
				next  string
			)
			err := c.fetch(ctx, nextURL, func(doc *goquery.Document) error {
				items, next = parseNotesInboxPage(doc)
				return nil
			}, reqOpts...)
			if err != nil {
				yield(nil, err)
				return
			}
			pagesFetched++
			for _, it := range items {
				if !yield(it, nil) {
					return
				}
			}
			if next == "" || len(items) == 0 {
				return
			}
			nextURL = next
		}
	}
}

// GetNote fetches a single note (private message) by ID. Requires a
// logged-in client.
func (c *Client) GetNote(ctx context.Context, id NoteID, opts ...Option) (*Note, error) {
	if id <= 0 {
		return nil, fmt.Errorf("fa: GetNote: id must be > 0")
	}
	var out *Note
	err := c.fetch(ctx, urls.ViewMessage(int64(id)), func(doc *goquery.Document) error {
		n, err := parseNote(id, doc)
		if err != nil {
			return err
		}
		out = n
		return nil
	}, opts...)
	if err != nil {
		return nil, err
	}
	return out, nil
}