package logtext

import (
	"bytes"
	"context"
	"fmt"
	"io"
	"strconv"

	"git.blauwelle.com/go/crate/log/logsdk"
	"git.blauwelle.com/go/crate/log/logsdk/logjson"
)

var _ logsdk.EntryProcessor = &Processor{}

func New(opts ...Option) *Processor {
	cfg := newConfig(opts...)
	return &Processor{
		bytesBufferPool: cfg.bytesBufferPool,
		output:          cfg.output,
		timeFormat:      cfg.timeFormat,
		timePadding:     cfg.timePadding,
		disableTime:     cfg.disableTime,
	}
}

type Processor struct {
	bytesBufferPool logjson.BytesBufferPool
	output          io.Writer
	timeFormat      string
	timePadding     int
	disableTime     bool
}

func (processor *Processor) Process(_ context.Context, entry logsdk.ReadonlyEntry) {
	buf := processor.bytesBufferPool.Get()
	buf.Reset()
	defer processor.bytesBufferPool.Put(buf)

	buf.Write(formatLevel(entry.Level))

	if !processor.disableTime {
		buf.WriteByte(' ')
		timeValue := entry.Time.Format(processor.timeFormat)
		buf.WriteString(timeValue)
		writeSpace(buf, processor.timePadding-len(timeValue))
	}

	for _, field := range entry.Fields {
		buf.WriteByte(' ')
		buf.WriteString(field.Key)
		buf.WriteByte('=')
		writeValue(buf, field.Value)
	}

	if entry.Message != "" {
		buf.WriteByte(' ')
		buf.WriteString(entry.Message)
	}

	buf.WriteByte('\n')

	if entry.Caller.IsValid() && len(entry.Stack) == 0 {
		writeFrame(buf, entry.Caller)
	}

	if len(entry.Stack) > 0 {
		for _, frame := range entry.Stack {
			writeFrame(buf, frame)
		}
	}

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

func writeSpace(buf *bytes.Buffer, n int) {
	for i := 0; i < n; i++ {
		buf.WriteByte(' ')
	}
}

func writeFrame(buf *bytes.Buffer, frame logsdk.Frame) {
	buf.WriteByte('|')
	buf.WriteByte(' ')
	buf.WriteString(frame.Function)
	buf.WriteByte('\n')
	buf.WriteByte('|')
	buf.WriteByte(' ')
	buf.WriteByte('\t')
	buf.WriteString(frame.File)
	buf.WriteByte(':')
	buf.WriteString(strconv.Itoa(frame.Line))
	buf.WriteByte('\n')
}

func writeValue(buf *bytes.Buffer, value any) {
	switch value := value.(type) {
	case nil:
		buf.WriteString("<nil>")
	case string:
		buf.WriteString(value)
	case error:
		buf.WriteString(value.Error())
	case fmt.Stringer:
		buf.WriteString(value.String())
	default:
		_, _ = fmt.Fprintf(buf, "%v", value)
	}
}

func formatLevel(level logsdk.Level) []byte {
	switch level {
	case logsdk.LevelPanic:
		return []byte(LevelPanicValue)
	case logsdk.LevelFatal:
		return []byte(LevelFatalValue)
	case logsdk.LevelError:
		return []byte(LevelErrorValue)
	case logsdk.LevelWarn:
		return []byte(LevelWarnValue)
	case logsdk.LevelInfo:
		return []byte(LevelInfoValue)
	case logsdk.LevelDebug:
		return []byte(LevelDebugValue)
	case logsdk.LevelTrace:
		return []byte(LevelTraceValue)
	case logsdk.LevelDisabled:
		fallthrough
	default:
		return []byte(levelUnknownValue)
	}
}

const (
	LevelPanicValue = "PNC"
	LevelFatalValue = "FTL"
	LevelErrorValue = "ERR"
	LevelWarnValue  = "WRN"
	LevelInfoValue  = "INF"
	LevelDebugValue = "DBG"
	LevelTraceValue = "TRC"

	levelUnknownValue = "UNK"
)