package aitools

import (
	"bufio"
	"encoding/json"
	"os"
	"time"
)

const mcpActiveWindow = 5 * time.Minute

// MCPStatus 供侧栏 MCP 状态点 / 设置页轻量指示。
type MCPStatus struct {
	Configured     bool         `json:"configured"`
	Mode           string       `json:"mode"`
	WhitelistCount int          `json:"whitelistCount"`
	WritesEnabled  bool         `json:"writesEnabled"`
	AllowDangerous bool         `json:"allowDangerous"`
	Active         bool         `json:"active"` // 近 5 分钟有 source=mcp 审计
	Recent         []AuditEntry `json:"recent,omitempty"`
	PolicyPath     string       `json:"policyPath,omitempty"`
	AuditPath      string       `json:"auditPath,omitempty"`
}

// GetMCPStatus 读 mcp.json + 尾部审计；不探测外部 Cursor 进程。
func GetMCPStatus() MCPStatus {
	st := MCPStatus{Mode: ModeReadOnly}
	if path, err := PolicyPath(); err == nil {
		st.PolicyPath = path
		if _, err := os.Stat(path); err == nil {
			st.Configured = true
		}
	}
	if p, err := LoadPolicy(); err == nil {
		st.Mode = p.Mode
		if st.Mode == "" {
			st.Mode = ModeReadOnly
		}
		st.WhitelistCount = len(p.AllowedConnectionIDs)
		st.WritesEnabled = p.WritesEnabled()
		st.AllowDangerous = p.AllowDangerous
		st.Configured = st.Configured || st.WhitelistCount > 0
	}
	if ap, err := AuditPath(); err == nil {
		st.AuditPath = ap
		recent := tailAudit(ap, 20)
		st.Recent = filterSource(recent, "mcp")
		if len(st.Recent) == 0 {
			// 兼容旧审计无 source：仍展示最近条目，但不标 active
			st.Recent = recent
		} else {
			cutoff := time.Now().Add(-mcpActiveWindow)
			for _, e := range st.Recent {
				if t, err := time.Parse(time.RFC3339, e.Time); err == nil && t.After(cutoff) {
					st.Active = true
					break
				}
			}
		}
	}
	return st
}

func filterSource(in []AuditEntry, source string) []AuditEntry {
	var out []AuditEntry
	for _, e := range in {
		if e.Source == source {
			out = append(out, e)
		}
	}
	return out
}

func tailAudit(path string, n int) []AuditEntry {
	f, err := os.Open(path)
	if err != nil {
		return nil
	}
	defer f.Close()
	var lines []string
	sc := bufio.NewScanner(f)
	sc.Buffer(make([]byte, 0, 64*1024), 1024*1024)
	for sc.Scan() {
		lines = append(lines, sc.Text())
		if len(lines) > n*4 { // 粗裁
			lines = lines[len(lines)-n*2:]
		}
	}
	if len(lines) > n {
		lines = lines[len(lines)-n:]
	}
	out := make([]AuditEntry, 0, len(lines))
	for _, line := range lines {
		var e AuditEntry
		if json.Unmarshal([]byte(line), &e) == nil {
			out = append(out, e)
		}
	}
	return out
}