package smtp

import (
	"context"
	"encoding/json"
	"log/slog"
	"time"

	"github.com/jackc/pgx/v5/pgxpool"
	"github.com/ultisuite/ulti-backend/internal/observability"
)

type OutboxProcessor struct {
	db       *pgxpool.Pool
	sender   *Sender
	logger   *slog.Logger
	interval time.Duration
}

func NewOutboxProcessor(db *pgxpool.Pool, sender *Sender, interval time.Duration) *OutboxProcessor {
	return &OutboxProcessor{
		db:       db,
		sender:   sender,
		logger:   slog.Default().With("component", "outbox"),
		interval: interval,
	}
}

func (p *OutboxProcessor) Start(ctx context.Context) {
	ticker := time.NewTicker(p.interval)
	defer ticker.Stop()

	p.logger.Info("outbox processor started", "interval", p.interval)

	for {
		select {
		case <-ctx.Done():
			p.logger.Info("outbox processor stopped")
			return
		case <-ticker.C:
			p.processScheduled(ctx)
			p.processQueue(ctx)
			p.updateQueueDepth(ctx)
		}
	}
}

func (p *OutboxProcessor) processQueue(ctx context.Context) {
	rows, err := p.db.Query(ctx, `
		UPDATE outbox SET status = 'sending', updated_at = NOW()
		WHERE id IN (
			SELECT id FROM outbox
			WHERE status = 'queued'
			ORDER BY created_at ASC
			LIMIT 10
			FOR UPDATE SKIP LOCKED
		)
		RETURNING id, account_id, to_addrs, cc_addrs, bcc_addrs, subject, body_text, body_html, in_reply_to, references_header
	`)
	if err != nil {
		p.logger.Error("failed to query outbox", "error", err)
		return
	}
	defer rows.Close()

	for rows.Next() {
		var (
			id         string
			accountID  string
			toJSON     []byte
			ccJSON     []byte
			bccJSON    []byte
			subject    string
			bodyText   string
			bodyHTML   string
			inReplyTo  string
			references []string
		)

		if err := rows.Scan(&id, &accountID, &toJSON, &ccJSON, &bccJSON, &subject, &bodyText, &bodyHTML, &inReplyTo, &references); err != nil {
			p.logger.Error("scan outbox row", "error", err)
			continue
		}

		to := parseJSONAddresses(toJSON)
		cc := parseJSONAddresses(ccJSON)
		bcc := parseJSONAddresses(bccJSON)

		// Get the from address
		var fromEmail string
		if err := p.db.QueryRow(ctx, `
			SELECT mi.email FROM mail_identities mi
			JOIN mail_accounts ma ON mi.account_id = ma.id
			WHERE ma.id = $1 AND mi.is_default = true
			LIMIT 1
		`, accountID).Scan(&fromEmail); err != nil || fromEmail == "" {
			if err := p.db.QueryRow(ctx, `SELECT email FROM mail_accounts WHERE id = $1`, accountID).Scan(&fromEmail); err != nil {
				p.logger.Error("resolve from address", "outbox_id", id, "account_id", accountID, "error", err)
				continue
			}
		}

		req := &SendRequest{
			AccountID:  accountID,
			From:       fromEmail,
			To:         to,
			Cc:         cc,
			Bcc:        bcc,
			Subject:    subject,
			BodyText:   bodyText,
			BodyHTML:   bodyHTML,
			InReplyTo:  inReplyTo,
			References: references,
		}

		if err := p.sender.Send(ctx, req); err != nil {
			p.logger.Error("send failed", "outbox_id", id, "error", err)
			observability.IncOutboxProcessed("error")
			if _, execErr := p.db.Exec(ctx, `
				UPDATE outbox SET status = 'queued', retry_count = retry_count + 1, error = $2, updated_at = NOW()
				WHERE id = $1
			`, id, err.Error()); execErr != nil {
				p.logger.Error("failed to mark outbox retry", "outbox_id", id, "error", execErr)
			}
		} else {
			observability.IncOutboxProcessed("success")
			if _, execErr := p.db.Exec(ctx, `
				UPDATE outbox SET status = 'sent', sent_at = NOW(), updated_at = NOW()
				WHERE id = $1
			`, id); execErr != nil {
				p.logger.Error("failed to mark outbox sent", "outbox_id", id, "error", execErr)
			}
		}
	}
	if err := rows.Err(); err != nil {
		p.logger.Error("iterate outbox rows", "error", err)
	}
}

func (p *OutboxProcessor) processScheduled(ctx context.Context) {
	result, err := p.db.Exec(ctx, `
		UPDATE outbox SET status = 'queued', updated_at = NOW()
		WHERE status = 'scheduled' AND scheduled_at IS NOT NULL AND scheduled_at <= NOW()
	`)
	if err != nil {
		p.logger.Error("failed to process scheduled", "error", err)
		return
	}
	if n := result.RowsAffected(); n > 0 {
		p.logger.Info("promoted scheduled outbox rows", "count", n)
	}
}

func (p *OutboxProcessor) updateQueueDepth(ctx context.Context) {
	var count int64
	err := p.db.QueryRow(ctx, `
		SELECT COUNT(*) FROM outbox
		WHERE status IN ('queued', 'scheduled', 'sending')
	`).Scan(&count)
	if err != nil {
		p.logger.Error("failed to compute outbox queue depth", "error", err)
		return
	}
	observability.SetOutboxQueueDepth(count)
}

func parseJSONAddresses(data []byte) []string {
	var addrs []struct {
		Address string `json:"address"`
	}
	if err := json.Unmarshal(data, &addrs); err != nil {
		// Try as plain string array
		var plain []string
		if err := json.Unmarshal(data, &plain); err == nil {
			return plain
		}
		return nil
	}
	result := make([]string, 0, len(addrs))
	for _, a := range addrs {
		result = append(result, a.Address)
	}
	return result
}