package agentserver

import (
	"net/url"
	"strings"
)

// OwnerKind 代理请求的归属校验方式
type OwnerKind int

const (
	// OwnerNone 只读元数据，无需归属校验（/v1/profiles、/v1/providers）
	OwnerNone OwnerKind = iota
	// OwnerSession 路径中的会话 ID
	OwnerSession
	// OwnerQuerySession 查询参数 sessionId
	OwnerQuerySession
	// OwnerRun 路径中的 runId
	OwnerRun
	// OwnerInteraction 路径中的 interactionId
	OwnerInteraction
	// OwnerFile 路径中的 fileId
	OwnerFile
)

// Action 需要特殊处理的接口
type Action int

const (
	ActionPassthrough   Action = iota
	ActionStream               // GET /sessions/:id/stream（SSE 透传 + 解析事件）
	ActionEvents               // GET /sessions/:id/events（解析事件）
	ActionSessionDetail        // GET /sessions/:id（记录 activeRunId、待处理交互）
	ActionSessionPatch         // PATCH /sessions/:id（只保留 title、model）
	ActionSendMessage          // POST /sessions/:id/messages（记录 runId、刷新 lastActive）
	ActionUploadFiles          // POST /sessions/:id/files（记录 fileId）
	ActionListFiles            // GET /sessions/:id/files（记录 fileId）
	ActionInteractions         // GET /interactions?sessionId=（记录 interactionId）
)

// Route 白名单匹配结果
type Route struct {
	Owner  OwnerKind
	Id     string // 用于归属校验的 ID（会话 / run / 交互 / 文件）
	Action Action
}

// MatchRoute 按白名单（technical-design §3.5）匹配代理请求。
// path 为 /v1 之后的部分（如 /sessions/ses_x/stream）；不在白名单内返回 false。
func MatchRoute(method, path string, query url.Values) (Route, bool) {
	seg := splitPath(path)
	n := len(seg)
	switch {
	case method == "GET" && n == 1 && (seg[0] == "profiles" || seg[0] == "providers"):
		return Route{Owner: OwnerNone}, true

	case n >= 2 && seg[0] == "sessions" && validId(seg[1], PrefixSession):
		id := seg[1]
		if n == 2 {
			switch method {
			case "GET":
				return Route{Owner: OwnerSession, Id: id, Action: ActionSessionDetail}, true
			case "PATCH":
				return Route{Owner: OwnerSession, Id: id, Action: ActionSessionPatch}, true
			}
			return Route{}, false
		}
		if n != 3 {
			return Route{}, false
		}
		switch {
		case method == "GET" && seg[2] == "events":
			return Route{Owner: OwnerSession, Id: id, Action: ActionEvents}, true
		case method == "GET" && seg[2] == "stream":
			return Route{Owner: OwnerSession, Id: id, Action: ActionStream}, true
		case method == "GET" && seg[2] == "files":
			return Route{Owner: OwnerSession, Id: id, Action: ActionListFiles}, true
		case method == "POST" && seg[2] == "files":
			return Route{Owner: OwnerSession, Id: id, Action: ActionUploadFiles}, true
		case method == "POST" && seg[2] == "messages":
			return Route{Owner: OwnerSession, Id: id, Action: ActionSendMessage}, true
		}
		return Route{}, false

	case n >= 2 && seg[0] == "runs" && validId(seg[1], PrefixRun):
		if (method == "GET" && n == 2) || (method == "POST" && n == 3 && seg[2] == "interrupt") {
			return Route{Owner: OwnerRun, Id: seg[1]}, true
		}
		return Route{}, false

	case method == "GET" && n == 1 && seg[0] == "interactions":
		sid := query.Get("sessionId")
		if !validId(sid, PrefixSession) {
			return Route{}, false
		}
		return Route{Owner: OwnerQuerySession, Id: sid, Action: ActionInteractions}, true

	case method == "POST" && n == 2 && seg[0] == "interactions" && validId(seg[1], PrefixInteraction):
		return Route{Owner: OwnerInteraction, Id: seg[1]}, true

	case method == "GET" && n == 2 && seg[0] == "files" && validId(seg[1], PrefixFile):
		return Route{Owner: OwnerFile, Id: seg[1]}, true
	}
	return Route{}, false
}

func splitPath(p string) []string {
	p = strings.Trim(p, "/")
	if p == "" {
		return nil
	}
	return strings.Split(p, "/")
}

// validId 校验带前缀的 ID，只允许字母、数字、下划线和连字符，防止路径穿越
func validId(id, prefix string) bool {
	if !strings.HasPrefix(id, prefix) || len(id) <= len(prefix) || len(id) > 64 {
		return false
	}
	for _, r := range id {
		if !(r >= 'a' && r <= 'z' || r >= 'A' && r <= 'Z' || r >= '0' && r <= '9' || r == '_' || r == '-') {
			return false
		}
	}
	return true
}

// ResourceKindOf 按前缀判断子资源类型
func ResourceKindOf(id string) OwnerKind {
	switch {
	case strings.HasPrefix(id, PrefixRun):
		return OwnerRun
	case strings.HasPrefix(id, PrefixInteraction):
		return OwnerInteraction
	case strings.HasPrefix(id, PrefixFile):
		return OwnerFile
	}
	return OwnerNone
}