package db

import (
	"fmt"
	"strings"
	"time"
)

const subnetSpreadFailureThreshold = 5
const subnetSpreadPauseDuration = 24 * time.Hour

// SubnetSpreadPause tracks /24 spread failure counts and temporary pauses.
type SubnetSpreadPause struct {
	Prefix      string    `json:"prefix"`
	FailCount   int       `json:"fail_count"`
	PausedUntil *time.Time `json:"paused_until,omitempty"`
	UpdatedAt   time.Time `json:"updated_at"`
}

func (d *Database) ensureSubnetSpreadPauseTable() error {
	if d == nil {
		return nil
	}
	_, err := d.Exec(`CREATE TABLE IF NOT EXISTS subnet_spread_pause (
		prefix TEXT PRIMARY KEY,
		fail_count INTEGER NOT NULL DEFAULT 0,
		paused_until DATETIME,
		updated_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP
	)`)
	if err != nil {
		return fmt.Errorf("subnet_spread_pause migration: %w", err)
	}
	_, _ = d.Exec(`CREATE INDEX IF NOT EXISTS idx_subnet_spread_pause_until ON subnet_spread_pause(paused_until)`)
	return nil
}

// RecordSubnetSpreadFailure increments failures for a /24 prefix; pauses at threshold.
func (d *Database) RecordSubnetSpreadFailure(prefix string) (paused bool, err error) {
	if err := d.ensureSubnetSpreadPauseTable(); err != nil {
		return false, err
	}
	prefix = normalizeSubnetPrefix(prefix)
	if prefix == "" {
		return false, fmt.Errorf("subnet prefix required")
	}
	now := time.Now().UTC()
	var failCount int
	err = d.QueryRow(`SELECT fail_count FROM subnet_spread_pause WHERE prefix = ?`, prefix).Scan(&failCount)
	if err != nil {
		_, err = d.Exec(
			`INSERT INTO subnet_spread_pause (prefix, fail_count, paused_until, updated_at) VALUES (?, 1, NULL, ?)`,
			prefix, now,
		)
		return false, err
	}
	failCount++
	var pausedUntil *time.Time
	if failCount >= subnetSpreadFailureThreshold {
		until := now.Add(subnetSpreadPauseDuration)
		pausedUntil = &until
		paused = true
	}
	if pausedUntil != nil {
		_, err = d.Exec(
			`UPDATE subnet_spread_pause SET fail_count = ?, paused_until = ?, updated_at = ? WHERE prefix = ?`,
			failCount, pausedUntil, now, prefix,
		)
	} else {
		_, err = d.Exec(
			`UPDATE subnet_spread_pause SET fail_count = ?, updated_at = ? WHERE prefix = ?`,
			failCount, now, prefix,
		)
	}
	return paused, err
}

// IsSubnetSpreadPaused reports whether spread commands to prefix are blocked.
func (d *Database) IsSubnetSpreadPaused(prefix string) (bool, error) {
	if err := d.ensureSubnetSpreadPauseTable(); err != nil {
		return false, err
	}
	prefix = normalizeSubnetPrefix(prefix)
	if prefix == "" {
		return false, nil
	}
	var pausedUntil *time.Time
	err := d.QueryRow(`SELECT paused_until FROM subnet_spread_pause WHERE prefix = ?`, prefix).Scan(&pausedUntil)
	if err != nil {
		return false, nil
	}
	if pausedUntil == nil {
		return false, nil
	}
	until := pausedUntil.UTC()
	if time.Now().UTC().Before(until) {
		return true, nil
	}
	_, _ = d.Exec(`UPDATE subnet_spread_pause SET paused_until = NULL, updated_at = ? WHERE prefix = ?`, time.Now().UTC(), prefix)
	return false, nil
}

// GetSubnetSpreadPause returns the pause row for UI / tests.
func (d *Database) GetSubnetSpreadPause(prefix string) (*SubnetSpreadPause, error) {
	if err := d.ensureSubnetSpreadPauseTable(); err != nil {
		return nil, err
	}
	prefix = normalizeSubnetPrefix(prefix)
	if prefix == "" {
		return nil, nil
	}
	row := &SubnetSpreadPause{Prefix: prefix}
	var pausedRaw *time.Time
	err := d.QueryRow(
		`SELECT fail_count, paused_until, updated_at FROM subnet_spread_pause WHERE prefix = ?`,
		prefix,
	).Scan(&row.FailCount, &pausedRaw, &row.UpdatedAt)
	if err != nil {
		return nil, nil
	}
	row.PausedUntil = pausedRaw
	return row, nil
}

func normalizeSubnetPrefix(prefix string) string {
	prefix = strings.TrimSpace(prefix)
	prefix = strings.TrimSuffix(prefix, ".0/24")
	prefix = strings.TrimSuffix(prefix, "/24")
	return prefix
}