package proxy

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

	"github.com/fonu/fonu/internal/validate"
)

type Host struct {
	ID         int64  `json:"id"`
	Hostname   string `json:"hostname"`
	ListenPort *int   `json:"listen_port,omitempty"`
}

type Rule struct {
	ID           int64          `json:"id"`
	Domain       string         `json:"domain"`
	Upstream     string         `json:"upstream"`
	ListenPort   int            `json:"listen_port"`
	ListenIPv4   bool           `json:"listen_ipv4"`
	ListenIPv6   bool           `json:"listen_ipv6"`
	Hosts        []Host         `json:"hosts"`
	HTTPSEnabled bool           `json:"https_enabled"`
	HTTPRedirect bool           `json:"http_redirect"`
	Enabled      bool           `json:"enabled"`
	NginxMode    string         `json:"nginx_mode"`
	Name         string         `json:"name"`
	SortOrder    int            `json:"sort_order"`
	Security     SecurityConfig `json:"security"`
	CreatedAt    time.Time      `json:"created_at"`
	UpdatedAt    time.Time      `json:"updated_at"`
}

type PortGroup struct {
	Port      int
	Hostnames []string
}

func (r Rule) PrimaryHost() string {
	if len(r.Hosts) > 0 {
		return r.Hosts[0].Hostname
	}
	return ""
}

type Endpoint struct {
	Hostname string
	Port     int
}

func (r Rule) Endpoints() []Endpoint {
	seen := make(map[string]bool)
	var out []Endpoint
	for _, host := range r.Hosts {
		name := strings.ToLower(strings.TrimSpace(host.Hostname))
		if name == "" {
			continue
		}
		port := hostEffectivePort(host, r.ListenPort)
		key := fmt.Sprintf("%s:%d", name, port)
		if seen[key] {
			continue
		}
		seen[key] = true
		out = append(out, Endpoint{Hostname: name, Port: port})
	}
	if len(out) == 0 {
		domain := strings.ToLower(strings.TrimSpace(r.Domain))
		if domain != "" {
			out = append(out, Endpoint{Hostname: domain, Port: r.ListenPort})
		}
	}
	return out
}

func (r Rule) Hostnames() []string {
	seen := make(map[string]bool)
	var names []string
	for _, host := range r.Hosts {
		name := strings.ToLower(strings.TrimSpace(host.Hostname))
		if name == "" || seen[name] {
			continue
		}
		seen[name] = true
		names = append(names, name)
	}
	if len(names) == 0 {
		domain := strings.ToLower(strings.TrimSpace(r.Domain))
		if domain != "" {
			names = append(names, domain)
		}
	}
	return names
}

func (r Rule) PortGroups() []PortGroup {
	groups := map[int][]string{}
	ports := make([]int, 0)
	for _, host := range r.Hosts {
		port := r.ListenPort
		if host.ListenPort != nil && *host.ListenPort > 0 {
			port = *host.ListenPort
		}
		if _, ok := groups[port]; !ok {
			ports = append(ports, port)
		}
		groups[port] = append(groups[port], host.Hostname)
	}

	out := make([]PortGroup, 0, len(ports))
	for _, port := range ports {
		out = append(out, PortGroup{Port: port, Hostnames: groups[port]})
	}
	return out
}

type CreateInput struct {
	Upstream     string
	ListenPort   int
	ListenIPv4   bool
	ListenIPv6   bool
	Hosts        []string
	HTTPSEnabled bool
	HTTPRedirect bool
	Enabled      bool
	Name         string
	Security     SecurityInput
}

type UpdateInput struct {
	Upstream     *string
	ListenPort   *int
	ListenIPv4   *bool
	ListenIPv6   *bool
	Hosts        *[]string
	HTTPSEnabled *bool
	HTTPRedirect *bool
	Enabled      *bool
	Name         *string
	Security     *SecurityInput
}

type Store struct {
	db *sql.DB
	tx *sql.Tx
}

func NewStore(db *sql.DB) *Store {
	return &Store{db: db}
}

func NewStoreWithTx(tx *sql.Tx) *Store {
	return &Store{tx: tx}
}

func (s *Store) querier() interface {
	QueryContext(context.Context, string, ...any) (*sql.Rows, error)
	QueryRowContext(context.Context, string, ...any) *sql.Row
	ExecContext(context.Context, string, ...any) (sql.Result, error)
} {
	if s.tx != nil {
		return s.tx
	}
	return s.db
}

func (s *Store) List(ctx context.Context) ([]Rule, error) {
	if err := s.cleanupOrphanRules(ctx); err != nil {
		return nil, err
	}
	q := s.querier()
	rows, err := q.QueryContext(ctx, `
		SELECT id, upstream, listen_port, listen_ipv4, listen_ipv6, https_enabled, http_redirect, enabled, nginx_mode, name, sort_order, security_json, created_at, updated_at
		FROM proxy_rules
		ORDER BY sort_order ASC, id ASC
	`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var rules []Rule
	for rows.Next() {
		rule, err := scanRule(rows)
		if err != nil {
			return nil, err
		}
		rules = append(rules, rule)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	return s.attachHosts(ctx, rules)
}

func (s *Store) Get(ctx context.Context, id int64) (Rule, error) {
	row := s.querier().QueryRowContext(ctx, `
		SELECT id, upstream, listen_port, listen_ipv4, listen_ipv6, https_enabled, http_redirect, enabled, nginx_mode, name, sort_order, security_json, created_at, updated_at
		FROM proxy_rules WHERE id = ?
	`, id)
	rule, err := scanRule(row)
	if errors.Is(err, sql.ErrNoRows) {
		return Rule{}, fmt.Errorf("规则不存在")
	}
	if err != nil {
		return Rule{}, err
	}
	rules, err := s.attachHosts(ctx, []Rule{rule})
	if err != nil {
		return Rule{}, err
	}
	return rules[0], nil
}

func (s *Store) Create(ctx context.Context, in CreateInput) (Rule, error) {
	upstream, hosts, err := validateCreateInput(in)
	if err != nil {
		return Rule{}, err
	}
	if err := s.ensureHostsAvailable(ctx, hosts, in.ListenPort, 0); err != nil {
		return Rule{}, err
	}

	name, err := normalizeName(in.Name)
	if err != nil {
		return Rule{}, err
	}
	sortOrder, err := s.nextSortOrder(ctx)
	if err != nil {
		return Rule{}, err
	}

	security, err := MergeSecurity(DefaultSecurityConfig(), in.Security)
	if err != nil {
		return Rule{}, err
	}
	securityJSON, err := security.ToJSON()
	if err != nil {
		return Rule{}, err
	}

	res, err := s.querier().ExecContext(ctx, `
		INSERT INTO proxy_rules(upstream, listen_port, listen_ipv4, listen_ipv6, https_enabled, http_redirect, enabled, name, sort_order, security_json, updated_at)
		VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, datetime('now'))
	`, upstream, in.ListenPort, boolInt(in.ListenIPv4), boolInt(in.ListenIPv6), boolInt(in.HTTPSEnabled), boolInt(in.HTTPRedirect), boolInt(in.Enabled), name, sortOrder, securityJSON)
	if err != nil {
		return Rule{}, err
	}
	id, err := res.LastInsertId()
	if err != nil {
		return Rule{}, err
	}
	if err := s.replaceHosts(ctx, id, in.ListenPort, hosts); err != nil {
		_, _ = s.querier().ExecContext(ctx, `DELETE FROM proxy_rules WHERE id = ?`, id)
		return Rule{}, err
	}
	return s.Get(ctx, id)
}

func (s *Store) Update(ctx context.Context, id int64, in UpdateInput) (Rule, error) {
	current, err := s.Get(ctx, id)
	if err != nil {
		return Rule{}, err
	}

	oldListenPort := current.ListenPort
	upstream := current.Upstream
	listenPort := current.ListenPort
	listenIPv4 := current.ListenIPv4
	listenIPv6 := current.ListenIPv6
	httpsEnabled := current.HTTPSEnabled
	httpRedirect := current.HTTPRedirect
	enabled := current.Enabled
	name := current.Name
	hosts := current.Hosts

	if in.Upstream != nil {
		upstream, err = validate.Upstream(*in.Upstream)
		if err != nil {
			return Rule{}, err
		}
	}
	if in.ListenPort != nil {
		if err := validate.ListenPort(*in.ListenPort); err != nil {
			return Rule{}, err
		}
		listenPort = *in.ListenPort
	}
	if in.ListenIPv4 != nil {
		listenIPv4 = *in.ListenIPv4
	}
	if in.ListenIPv6 != nil {
		listenIPv6 = *in.ListenIPv6
	}
	if !listenIPv4 && !listenIPv6 {
		return Rule{}, fmt.Errorf("至少需要启用 IPv4 或 IPv6 监听")
	}
	if in.HTTPSEnabled != nil {
		httpsEnabled = *in.HTTPSEnabled
	}
	if in.HTTPRedirect != nil {
		httpRedirect = *in.HTTPRedirect
	}
	if in.Enabled != nil {
		enabled = *in.Enabled
	}
	if in.Name != nil {
		name, err = normalizeName(*in.Name)
		if err != nil {
			return Rule{}, err
		}
	}
	if in.Hosts != nil {
		hosts, err = parseHosts(*in.Hosts, listenPort)
		if err != nil {
			return Rule{}, err
		}
		if len(hosts) == 0 {
			return Rule{}, fmt.Errorf("至少需要一个前端域名")
		}
	}

	security := current.Security
	if in.Security != nil {
		security, err = MergeSecurity(current.Security, *in.Security)
		if err != nil {
			return Rule{}, err
		}
	}
	securityJSON, err := security.ToJSON()
	if err != nil {
		return Rule{}, err
	}

	if in.ListenPort != nil && *in.ListenPort != oldListenPort && in.Hosts == nil {
		for _, host := range current.Hosts {
			if hostEffectivePort(host, oldListenPort) != oldListenPort {
				continue
			}
			if err := s.ensureHostAvailable(ctx, host.Hostname, listenPort, id); err != nil {
				return Rule{}, err
			}
		}
	}

	_, err = s.querier().ExecContext(ctx, `
		UPDATE proxy_rules
		SET upstream = ?, listen_port = ?, listen_ipv4 = ?, listen_ipv6 = ?, https_enabled = ?, http_redirect = ?, enabled = ?, name = ?, security_json = ?, updated_at = datetime('now')
		WHERE id = ?
	`, upstream, listenPort, boolInt(listenIPv4), boolInt(listenIPv6), boolInt(httpsEnabled), boolInt(httpRedirect), boolInt(enabled), name, securityJSON, id)
	if err != nil {
		return Rule{}, err
	}
	if in.ListenPort != nil && *in.ListenPort != oldListenPort && in.Hosts == nil {
		if _, err := s.querier().ExecContext(ctx, `
			UPDATE proxy_hosts SET listen_port = ? WHERE rule_id = ? AND listen_port = ?
		`, listenPort, id, oldListenPort); err != nil {
			if isUniqueViolation(err) {
				// 保存前校验与写入之间存在窗口，被并发规则抢占时按域名复检并给出带规则名的原因
				for _, host := range current.Hosts {
					if hostEffectivePort(host, oldListenPort) != oldListenPort {
						continue
					}
					if ownerErr := s.ensureHostAvailable(ctx, host.Hostname, listenPort, id); ownerErr != nil {
						return Rule{}, ownerErr
					}
				}
			}
			return Rule{}, err
		}
	}
	if in.Hosts != nil {
		if err := s.ensureHostsAvailable(ctx, hosts, listenPort, id); err != nil {
			return Rule{}, err
		}
		if err := s.replaceHosts(ctx, id, listenPort, hosts); err != nil {
			return Rule{}, err
		}
	}
	return s.Get(ctx, id)
}

func (s *Store) SetNginxMode(ctx context.Context, id int64, mode string) error {
	mode = strings.TrimSpace(mode)
	if mode != "auto" && mode != "custom" {
		return fmt.Errorf("无效的 nginx 模式")
	}
	res, err := s.querier().ExecContext(ctx, `
		UPDATE proxy_rules SET nginx_mode = ?, updated_at = datetime('now') WHERE id = ?
	`, mode, id)
	if err != nil {
		return err
	}
	n, err := res.RowsAffected()
	if err != nil {
		return err
	}
	if n == 0 {
		return fmt.Errorf("规则不存在")
	}
	return nil
}

func (s *Store) Delete(ctx context.Context, id int64) error {
	res, err := s.querier().ExecContext(ctx, `DELETE FROM proxy_rules WHERE id = ?`, id)
	if err != nil {
		return err
	}
	n, err := res.RowsAffected()
	if err != nil {
		return err
	}
	if n == 0 {
		return fmt.Errorf("规则不存在")
	}
	return nil
}

func (s *Store) ListEnabled(ctx context.Context) ([]Rule, error) {
	rows, err := s.querier().QueryContext(ctx, `
		SELECT id, upstream, listen_port, listen_ipv4, listen_ipv6, https_enabled, http_redirect, enabled, nginx_mode, name, sort_order, security_json, created_at, updated_at
		FROM proxy_rules WHERE enabled = 1 ORDER BY sort_order ASC, id ASC
	`)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var rules []Rule
	for rows.Next() {
		rule, err := scanRule(rows)
		if err != nil {
			return nil, err
		}
		rules = append(rules, rule)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}
	return s.attachHosts(ctx, rules)
}

func validateCreateInput(in CreateInput) (string, []Host, error) {
	upstream, err := validate.Upstream(in.Upstream)
	if err != nil {
		return "", nil, err
	}
	if err := validate.ListenPort(in.ListenPort); err != nil {
		return "", nil, err
	}
	if !in.ListenIPv4 && !in.ListenIPv6 {
		return "", nil, fmt.Errorf("至少需要启用 IPv4 或 IPv6 监听")
	}
	hosts, err := parseHosts(in.Hosts, in.ListenPort)
	if err != nil {
		return "", nil, err
	}
	if len(hosts) == 0 {
		return "", nil, fmt.Errorf("至少需要一个前端域名")
	}
	return upstream, hosts, nil
}

func (s *Store) cleanupOrphanRules(ctx context.Context) error {
	_, err := s.querier().ExecContext(ctx, `
		DELETE FROM proxy_rules
		WHERE id NOT IN (SELECT rule_id FROM proxy_hosts)
	`)
	return err
}

// isUniqueViolation 判断是否为 SQLite 唯一约束冲突（hostname + listen_port 撞车）
func isUniqueViolation(err error) bool {
	return err != nil && strings.Contains(strings.ToUpper(err.Error()), "UNIQUE")
}

func hostEffectivePort(host Host, ruleListenPort int) int {
	if host.ListenPort != nil && *host.ListenPort > 0 {
		return *host.ListenPort
	}
	return ruleListenPort
}

func parseHosts(raw []string, ruleListenPort int) ([]Host, error) {
	seen := make(map[string]struct{})
	hosts := make([]Host, 0, len(raw))
	for _, item := range raw {
		hostname, port, err := validate.FrontendAddress(item)
		if err != nil {
			return nil, err
		}
		effectivePort := ruleListenPort
		if port > 0 {
			effectivePort = port
		}
		key := fmt.Sprintf("%s:%d", strings.ToLower(hostname), effectivePort)
		if _, ok := seen[key]; ok {
			return nil, fmt.Errorf("前端域名 %s:%d 重复", hostname, effectivePort)
		}
		seen[key] = struct{}{}
		host := Host{Hostname: hostname}
		if port > 0 {
			host.ListenPort = &port
		}
		hosts = append(hosts, host)
	}
	return hosts, nil
}

func (s *Store) ensureHostAvailable(ctx context.Context, hostname string, port int, excludeRuleID int64) error {
	owner, err := s.endpointOwner(ctx, "proxy_hosts", hostname, port, excludeRuleID)
	if err != nil {
		return err
	}
	if owner != "" {
		return fmt.Errorf("域名 %s:%d 已被%s使用，请编辑现有规则或更换域名/端口", hostname, port, owner)
	}
	// 手动（custom）Nginx 规则的占用单独存表，其域名/端口不在 proxy_hosts 里，需一并检查
	owner, err = s.endpointOwner(ctx, "proxy_custom_endpoints", hostname, port, excludeRuleID)
	if err != nil {
		return err
	}
	if owner != "" {
		return fmt.Errorf("域名 %s:%d 已被%s使用（该规则使用手动 Nginx 配置），请编辑现有规则或更换域名/端口", hostname, port, owner)
	}
	return nil
}

// endpointOwner 返回占用该 (域名, 端口) 的规则描述（如 规则「名称」）；空闲时返回空串。
// table 只传入本包内两张固定表名（proxy_hosts / proxy_custom_endpoints），不接受外部输入。
// 规则描述优先用备注名，其次用该规则的首个域名，最后回落为规则 ID。
func (s *Store) endpointOwner(ctx context.Context, table, hostname string, port int, excludeRuleID int64) (string, error) {
	var (
		ownerID   int64
		ownerDesc string
	)
	query := `SELECT h.rule_id,
			COALESCE(NULLIF(TRIM(r.name), ''),
				(SELECT hostname FROM proxy_hosts WHERE rule_id = h.rule_id ORDER BY id LIMIT 1), '')
		FROM ` + table + ` h
		LEFT JOIN proxy_rules r ON r.id = h.rule_id
		WHERE h.hostname = ? COLLATE NOCASE AND h.listen_port = ? AND h.rule_id != ?
		LIMIT 1`
	err := s.querier().QueryRowContext(ctx, query, hostname, port, excludeRuleID).Scan(&ownerID, &ownerDesc)
	if errors.Is(err, sql.ErrNoRows) {
		return "", nil
	}
	if err != nil {
		return "", err
	}
	if desc := strings.TrimSpace(ownerDesc); desc != "" {
		return fmt.Sprintf("规则「%s」", desc), nil
	}
	return fmt.Sprintf("规则 #%d", ownerID), nil
}

func (s *Store) ensureHostsAvailable(ctx context.Context, hosts []Host, ruleListenPort int, excludeRuleID int64) error {
	for _, host := range hosts {
		port := hostEffectivePort(host, ruleListenPort)
		if err := s.ensureHostAvailable(ctx, host.Hostname, port, excludeRuleID); err != nil {
			return err
		}
	}
	return nil
}

func (s *Store) replaceHosts(ctx context.Context, ruleID int64, ruleListenPort int, hosts []Host) error {
	if _, err := s.querier().ExecContext(ctx, `DELETE FROM proxy_hosts WHERE rule_id = ?`, ruleID); err != nil {
		return err
	}
	for _, host := range hosts {
		port := hostEffectivePort(host, ruleListenPort)
		_, err := s.querier().ExecContext(ctx, `
			INSERT INTO proxy_hosts(rule_id, hostname, listen_port)
			VALUES (?, ?, ?)
		`, ruleID, host.Hostname, port)
		if err != nil {
			if isUniqueViolation(err) {
				// 并发下可能绕过保存前校验：复检一次以给出带规则名的原因
				if ownerErr := s.ensureHostAvailable(ctx, host.Hostname, port, ruleID); ownerErr != nil {
					return ownerErr
				}
				return fmt.Errorf("域名 %s:%d 已被其它规则占用", host.Hostname, port)
			}
			return err
		}
	}
	return nil
}

func (s *Store) attachHosts(ctx context.Context, rules []Rule) ([]Rule, error) {
	if len(rules) == 0 {
		return rules, nil
	}
	ids := make([]string, len(rules))
	args := make([]any, len(rules))
	for i, rule := range rules {
		ids[i] = "?"
		args[i] = rule.ID
	}

	query := `
		SELECT id, rule_id, hostname, listen_port
		FROM proxy_hosts
		WHERE rule_id IN (` + strings.Join(ids, ",") + `)
		ORDER BY id ASC
	`
	rows, err := s.querier().QueryContext(ctx, query, args...)
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	byRule := make(map[int64][]Host)
	for rows.Next() {
		var host Host
		var ruleID int64
		var listenPort sql.NullInt64
		if err := rows.Scan(&host.ID, &ruleID, &host.Hostname, &listenPort); err != nil {
			return nil, err
		}
		if listenPort.Valid {
			port := int(listenPort.Int64)
			host.ListenPort = &port
		}
		byRule[ruleID] = append(byRule[ruleID], host)
	}
	if err := rows.Err(); err != nil {
		return nil, err
	}

	for i := range rules {
		rules[i].Hosts = byRule[rules[i].ID]
		rules[i].Domain = rules[i].PrimaryHost()
	}
	return rules, nil
}

type rowScanner interface {
	Scan(dest ...any) error
}

func scanRule(row rowScanner) (Rule, error) {
	var rule Rule
	var listenIPv4 int
	var listenIPv6 int
	var httpsEnabled int
	var httpRedirect int
	var enabled int
	var nginxMode string
	var securityJSON string
	var createdAt string
	var updatedAt string
	if err := row.Scan(
		&rule.ID,
		&rule.Upstream,
		&rule.ListenPort,
		&listenIPv4,
		&listenIPv6,
		&httpsEnabled,
		&httpRedirect,
		&enabled,
		&nginxMode,
		&rule.Name,
		&rule.SortOrder,
		&securityJSON,
		&createdAt,
		&updatedAt,
	); err != nil {
		return Rule{}, err
	}
	rule.ListenIPv4 = listenIPv4 == 1
	rule.ListenIPv6 = listenIPv6 == 1
	rule.HTTPSEnabled = httpsEnabled == 1
	rule.HTTPRedirect = httpRedirect == 1
	rule.Enabled = enabled == 1
	if nginxMode == "" {
		nginxMode = "auto"
	}
	rule.NginxMode = nginxMode
	security, err := ParseSecurityJSON(securityJSON)
	if err != nil {
		return Rule{}, err
	}
	rule.Security = security
	rule.CreatedAt = parseTime(createdAt)
	rule.UpdatedAt = parseTime(updatedAt)
	return rule, nil
}

func parseTime(v string) time.Time {
	t, err := time.Parse("2006-01-02 15:04:05", v)
	if err != nil {
		t, _ = time.Parse(time.RFC3339, v)
	}
	return t.UTC()
}

func boolInt(v bool) int {
	if v {
		return 1
	}
	return 0
}

func normalizeName(raw string) (string, error) {
	name := strings.TrimSpace(raw)
	if len(name) > 100 {
		return "", fmt.Errorf("名称不能超过 100 个字符")
	}
	return name, nil
}

func (s *Store) nextSortOrder(ctx context.Context) (int, error) {
	var maxOrder sql.NullInt64
	err := s.querier().QueryRowContext(ctx, `SELECT MAX(sort_order) FROM proxy_rules`).Scan(&maxOrder)
	if err != nil {
		return 0, err
	}
	if !maxOrder.Valid {
		return 0, nil
	}
	return int(maxOrder.Int64) + 1, nil
}

func (s *Store) Reorder(ctx context.Context, ids []int64) error {
	if len(ids) == 0 {
		return nil
	}
	seen := make(map[int64]struct{}, len(ids))
	for _, id := range ids {
		if id <= 0 {
			return fmt.Errorf("无效的规则 ID")
		}
		if _, ok := seen[id]; ok {
			return fmt.Errorf("排序列表包含重复的规则 ID")
		}
		seen[id] = struct{}{}
	}

	var total int
	if err := s.querier().QueryRowContext(ctx, `SELECT COUNT(*) FROM proxy_rules`).Scan(&total); err != nil {
		return err
	}
	if len(ids) != total {
		return fmt.Errorf("排序列表必须包含全部规则")
	}

	tx, err := s.db.BeginTx(ctx, nil)
	if err != nil {
		return err
	}
	defer tx.Rollback()

	for index, id := range ids {
		res, err := tx.ExecContext(ctx, `UPDATE proxy_rules SET sort_order = ?, updated_at = datetime('now') WHERE id = ?`, index, id)
		if err != nil {
			return err
		}
		n, err := res.RowsAffected()
		if err != nil {
			return err
		}
		if n == 0 {
			return fmt.Errorf("规则不存在")
		}
	}
	return tx.Commit()
}