package utils

import (
	"fmt"
	"io"
	"os"
	"sync"
	"time"
)

// LogEntry 日志条目
type LogEntry struct {
	Time    time.Time `json:"time"`
	Level   string    `json:"level"`
	Message string    `json:"message"`
}

// LogBuffer 环形日志缓冲区
type LogBuffer struct {
	mu      sync.RWMutex
	entries []LogEntry
	maxSize int
	writer  io.Writer // 原始输出(控制台)
}

var LogBuf = NewLogBuffer(2000)

func NewLogBuffer(maxSize int) *LogBuffer {
	return &LogBuffer{
		entries: make([]LogEntry, 0, maxSize),
		maxSize: maxSize,
		writer:  os.Stderr,
	}
}

// Write 实现 io.Writer 接口, 用于 log.SetOutput
func (b *LogBuffer) Write(p []byte) (n int, err error) {
	// 写入原始输出
	b.writer.Write(p)

	msg := string(p)
	level := "INFO"
	switch {
	case contains(msg, "FAIL") || contains(msg, "Error") || contains(msg, "error"):
		level = "ERROR"
	case contains(msg, "WARN") || contains(msg, "warn"):
		level = "WARN"
	}

	b.mu.Lock()
	b.entries = append(b.entries, LogEntry{
		Time:    time.Now(),
		Level:   level,
		Message: msg,
	})
	// 超过上限则截掉前半部分
	if len(b.entries) > b.maxSize {
		b.entries = b.entries[len(b.entries)-b.maxSize:]
	}
	b.mu.Unlock()

	return len(p), nil
}

// Get 获取最近 n 条日志
func (b *LogBuffer) Get(n int) []LogEntry {
	b.mu.RLock()
	defer b.mu.RUnlock()

	total := len(b.entries)
	if n <= 0 || n > total {
		n = total
	}
	result := make([]LogEntry, n)
	copy(result, b.entries[total-n:])
	return result
}

// Count 日志总数
func (b *LogBuffer) Count() int {
	b.mu.RLock()
	defer b.mu.RUnlock()
	return len(b.entries)
}

func contains(s, sub string) bool {
	return len(s) >= len(sub) && (s == sub || len(s) > 0 && findSubstring(s, sub))
}

func findSubstring(s, sub string) bool {
	for i := 0; i <= len(s)-len(sub); i++ {
		if s[i:i+len(sub)] == sub {
			return true
		}
	}
	return false
}

// Logf 写入一条格式化日志到缓冲区
func Logf(format string, args ...interface{}) {
	msg := fmt.Sprintf(format, args...)
	LogBuf.Write([]byte(msg + "\n"))
}