// Reply-draft persistence for Phase 5 (FR-8).
//
// A draft belongs to one message. It is rewritten in place while Sam edits it
// and marked `sent` after a successful SMTP send. Only the newest draft per
// message is shown in the UI; history is kept in the actions_log (FR-13).
package store

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"time"
)

// Draft statuses. A draft moves draft -> sent once, on a successful send.
const (
	DraftStatusDraft = "draft"
	DraftStatusSent  = "sent"
)

// Draft is one reply draft row.
type Draft struct {
	ID         int64
	MessageID  int64
	Body       string
	TemplateID string
	Status     string
	SentAt     time.Time
	CreatedAt  time.Time
	UpdatedAt  time.Time
}

// SaveDraft inserts a new draft for a message and returns it.
func (s *Store) SaveDraft(ctx context.Context, messageID int64, body, templateID string) (Draft, error) {
	const q = `INSERT INTO drafts (message_id, body, template_id, status)
        VALUES (?, ?, ?, 'draft')`
	res, err := s.db.ExecContext(ctx, q, messageID, body, nullString(templateID))
	if err != nil {
		return Draft{}, fmt.Errorf("save draft for message %d: %w", messageID, err)
	}
	id, err := res.LastInsertId()
	if err != nil {
		return Draft{}, fmt.Errorf("read draft id: %w", err)
	}
	return s.DraftByID(ctx, id)
}

// DraftByID loads one draft.
func (s *Store) DraftByID(ctx context.Context, id int64) (Draft, error) {
	const q = `
SELECT id, message_id, body, COALESCE(template_id, ''), status,
       COALESCE(sent_at, ''), created_at, updated_at
FROM drafts WHERE id = ?`
	return scanDraft(s.db.QueryRowContext(ctx, q, id))
}

// LatestDraft returns the newest draft for a message. ok is false when the
// message has no draft yet.
func (s *Store) LatestDraft(ctx context.Context, messageID int64) (Draft, bool, error) {
	const q = `
SELECT id, message_id, body, COALESCE(template_id, ''), status,
       COALESCE(sent_at, ''), created_at, updated_at
FROM drafts WHERE message_id = ? ORDER BY id DESC LIMIT 1`
	d, err := scanDraft(s.db.QueryRowContext(ctx, q, messageID))
	if errors.Is(err, sql.ErrNoRows) {
		return Draft{}, false, nil
	}
	if err != nil {
		return Draft{}, false, err
	}
	return d, true, nil
}

// UpdateDraftBody replaces the body of a draft Sam edited and bumps updated_at.
func (s *Store) UpdateDraftBody(ctx context.Context, id int64, body string) error {
	const q = `UPDATE drafts SET body = ?, updated_at = datetime('now') WHERE id = ?`
	res, err := s.db.ExecContext(ctx, q, body, id)
	if err != nil {
		return fmt.Errorf("update draft %d: %w", id, err)
	}
	if n, _ := res.RowsAffected(); n == 0 {
		return fmt.Errorf("update draft %d: not found", id)
	}
	return nil
}

// MarkDraftSent records a successful send.
func (s *Store) MarkDraftSent(ctx context.Context, id int64) error {
	const q = `UPDATE drafts SET status = 'sent', sent_at = datetime('now'),
        updated_at = datetime('now') WHERE id = ?`
	res, err := s.db.ExecContext(ctx, q, id)
	if err != nil {
		return fmt.Errorf("mark draft %d sent: %w", id, err)
	}
	if n, _ := res.RowsAffected(); n == 0 {
		return fmt.Errorf("mark draft %d sent: not found", id)
	}
	return nil
}

func scanDraft(row *sql.Row) (Draft, error) {
	var (
		d       Draft
		sentAt  string
		created string
		updated string
	)
	if err := row.Scan(&d.ID, &d.MessageID, &d.Body, &d.TemplateID, &d.Status,
		&sentAt, &created, &updated); err != nil {
		return Draft{}, err
	}
	d.SentAt = parseSQLTime(sentAt)
	d.CreatedAt = parseSQLTime(created)
	d.UpdatedAt = parseSQLTime(updated)
	return d, nil
}