package jsonlog

import (
	"encoding/json"
	"fmt"
	"io"
	"os"
	"time"

	"git.blauwelle.com/go/crate/log/logsdk"
	"git.blauwelle.com/go/crate/runtimehelper"
	"git.blauwelle.com/go/crate/synchelper"
)

var _ logsdk.EntryProcessor = &Processor{}

// New 返回日志处理对象,
// 返回的对象是 [logsdk.EntryProcessor].
func New(opts ...Option) *Processor {
	cfg := defaultConfig()
	for _, opt := range opts {
		opt.apply(cfg)
	}
	return &Processor{
		bufferPool:        cfg.pool,
		output:            cfg.output,
		timeFormat:        cfg.timestampFormat,
		disableTime:       cfg.disableTime,
		disableHTMLEscape: cfg.disableHTMLEscape,
		prettyPrint:       cfg.prettyPrint,
	}
}

// Processor 日志处理对象, 把日志处理成 JSON.
type Processor struct {
	bufferPool        synchelper.BytesBufferPool
	output            io.Writer
	timeFormat        string
	disableTime       bool
	disableHTMLEscape bool
	prettyPrint       bool
}

// Process 处理日志
func (processor *Processor) Process(entry logsdk.ReadonlyEntry) {
	m := Entry{
		Stack:   entry.Stack,
		Fields:  entry.Fields,
		Level:   entry.Level,
		Message: entry.Message,
	}
	if !processor.disableTime {
		m.Time = entry.Time.Format(processor.timeFormat) // 1次分配
	}
	if entry.Caller.IsValid() {
		// 1次分配
		// 直接取 &entry.Caller 会增加堆内存分配
		m.Caller = &runtimehelper.Frame{
			Function: entry.Caller.Function,
			File:     entry.Caller.File,
			Line:     entry.Caller.Line,
		}
	}

	buf := processor.bufferPool.Get()
	buf.Reset()
	defer processor.bufferPool.Put(buf)

	encoder := json.NewEncoder(buf)
	if processor.prettyPrint {
		encoder.SetIndent("", "  ")
	}
	encoder.SetEscapeHTML(!processor.disableHTMLEscape)

	// Encode 2次分配
	if err := encoder.Encode(m); err != nil {
		_, _ = fmt.Fprintf(os.Stderr, "JSON processor cannot encode log %#v: %s\n", m, err.Error())
	}

	if _, err := buf.WriteTo(processor.output); err != nil {
		_, _ = fmt.Fprintf(os.Stderr, "JSON processor cannot write log: %s\n", err.Error())
	}
}

// Option 配置日志处理对象
type Option interface {
	apply(cfg *config)
}

// WithBufferPool 配置缓冲池
func WithBufferPool(pool synchelper.BytesBufferPool) Option {
	return optionFunc(func(cfg *config) {
		cfg.pool = pool
	})
}

// WithOutput 配置输出
func WithOutput(w io.Writer) Option {
	return optionFunc(func(cfg *config) {
		cfg.output = w
	})
}

// WithTimeFormat 配置时间格式
func WithTimeFormat(format string) Option {
	return optionFunc(func(cfg *config) {
		cfg.timestampFormat = format
	})
}

// WithDisableTime 配置仅用时间输出
func WithDisableTime(disable bool) Option {
	return optionFunc(func(cfg *config) {
		cfg.disableTime = disable
	})
}

// WithDisableHTMLEscape 配置禁止 HTML 转义
func WithDisableHTMLEscape(disable bool) Option {
	return optionFunc(func(cfg *config) {
		cfg.disableHTMLEscape = disable
	})
}

// WithPrettyPrint 配置 JSON 多行缩进输出
func WithPrettyPrint(pretty bool) Option {
	return optionFunc(func(cfg *config) {
		cfg.prettyPrint = pretty
	})
}

// Entry 被用来 JSON 序列化
type Entry struct {
	Message string                `json:"msg"`
	Time    string                `json:"time,omitempty"`
	Caller  *runtimehelper.Frame  `json:"caller,omitempty"`
	Stack   []runtimehelper.Frame `json:"stack,omitempty"`
	Fields  []logsdk.Field        `json:"fields,omitempty"`
	Level   logsdk.Level          `json:"level"`
}

func defaultConfig() *config {
	return &config{
		pool:              synchelper.NewBytesBufferPool(512, 2048),
		output:            synchelper.NewSyncWriter(os.Stderr),
		timestampFormat:   time.RFC3339Nano,
		disableTime:       false,
		disableHTMLEscape: false,
		prettyPrint:       false,
	}
}

type config struct {
	pool              synchelper.BytesBufferPool
	output            io.Writer
	timestampFormat   string
	disableTime       bool
	disableHTMLEscape bool
	prettyPrint       bool
}

type optionFunc func(cfg *config)

func (fn optionFunc) apply(cfg *config) {
	fn(cfg)
}