github.com/keakon/golog@v0.0.0-20230330091222-cac71197c18d/formatter.go

package golog

import (
	"bytes"
	"fmt"
	"os"
)

var unknownFile = []byte("???")

var (
	// DefaultFormatter is the default formatter
	DefaultFormatter = ParseFormat("[%l %D %T %s] %m")
	// TimedRotatingFormatter is a formatter for TimedRotatingFileWriter
	TimedRotatingFormatter = ParseFormat("[%l %T %s] %m")
)

// A Formatter containing a sequence of FormatParts.
type Formatter struct {
	formatParts []FormatPart
}

// ParseFormat parses a format string into a formatter.
func ParseFormat(format string) (formatter *Formatter) {
	if format == "" {
		return
	}
	formatter = &Formatter{}
	formatter.findParts([]byte(format))
	formatter.appendByte('\n')
	return
}

/*
Format formats a record to a bytes.Buffer.
Supported format directives:

	%%: %
	%l: short name of the level
	%T: time string (HH:MM:SS)
	%D: date string (YYYY-mm-DD)
	%s: source code string (filename:line)
	%S: full source code string (/path/filename.go:line)
*/
func (f *Formatter) Format(r *Record, buf *bytes.Buffer) {
	for _, part := range f.formatParts {
		part.Format(r, buf)
	}
}

func (f *Formatter) findParts(format []byte) {
	length := len(format)
	index := bytes.IndexByte(format, '%')
	if index == -1 || index == length-1 {
		if length == 0 {
			return
		}
		if length == 1 {
			f.appendByte(format[0])
		} else {
			f.appendBytes(format)
		}
		return
	}

	if index > 1 {
		f.appendBytes(format[:index])
	} else if index == 1 {
		f.appendByte(format[0])
	}
	switch c := format[index+1]; c {
	case '%':
		f.appendByte('%')
	case 'l':
		f.formatParts = append(f.formatParts, &LevelFormatPart{})
	case 'T':
		f.formatParts = append(f.formatParts, &TimeFormatPart{})
	case 'D':
		f.formatParts = append(f.formatParts, &DateFormatPart{})
	case 's':
		f.formatParts = append(f.formatParts, &SourceFormatPart{})
	case 'S':
		f.formatParts = append(f.formatParts, &FullSourceFormatPart{})
	case 'm':
		f.formatParts = append(f.formatParts, &MessageFormatPart{})
	default:
		f.appendBytes([]byte{'%', c})
	}
	f.findParts(format[index+2:])
	return
}

// FormatPart is an interface containing the Format() method.
type FormatPart interface {
	Format(r *Record, buf *bytes.Buffer)
}

// ByteFormatPart is a FormatPart containing a byte.
type ByteFormatPart struct {
	byte byte
}

// Format writes its byte to the buf.
func (p *ByteFormatPart) Format(r *Record, buf *bytes.Buffer) {
	buf.WriteByte(p.byte)
}

// appendByte appends a byte to the formatter.
// If the previous FormatPart is a ByteFormatPart or BytesFormatPart, they will be merged into a BytesFormatPart;
// otherwise a new ByteFormatPart will be created.
func (f *Formatter) appendByte(b byte) {
	parts := f.formatParts
	count := len(parts)
	if count == 0 {
		f.formatParts = append(parts, &ByteFormatPart{byte: b})
	} else {
		var p FormatPart
		lastPart := parts[count-1]
		switch lp := lastPart.(type) {
		case *ByteFormatPart:
			p = &BytesFormatPart{
				bytes: []byte{lp.byte, b},
			}
		case *BytesFormatPart:
			p = &BytesFormatPart{
				bytes: append(lp.bytes, b),
			}
		default:
			p = &ByteFormatPart{byte: b}
			f.formatParts = append(parts, p)
			return
		}
		f.formatParts[count-1] = p
	}
}

// BytesFormatPart is a FormatPart containing a byte slice.
type BytesFormatPart struct {
	bytes []byte
}

// Format writes its bytes to the buf.
func (p *BytesFormatPart) Format(r *Record, buf *bytes.Buffer) {
	buf.Write(p.bytes)
}

// appendBytes appends a byte slice to the formatter.
// If the previous FormatPart is a ByteFormatPart or BytesFormatPart, they will be merged into a BytesFormatPart;
// otherwise a new BytesFormatPart will be created.
func (f *Formatter) appendBytes(bs []byte) {
	parts := f.formatParts
	count := len(parts)
	if count == 0 {
		f.formatParts = append(parts, &BytesFormatPart{bytes: bs})
	} else {
		var p FormatPart
		lastPart := parts[count-1]
		switch lp := lastPart.(type) {
		case *ByteFormatPart: // won't reach here
			p = &BytesFormatPart{
				bytes: append([]byte{lp.byte}, bs...),
			}
		case *BytesFormatPart:
			p = &BytesFormatPart{
				bytes: append(lp.bytes, bs...),
			}
		default:
			p = &BytesFormatPart{bytes: bs}
			f.formatParts = append(parts, p)
			return
		}
		f.formatParts[count-1] = p
	}
}

// LevelFormatPart is a FormatPart of the level placeholder.
type LevelFormatPart struct{}

// Format writes the short level name of the record to the buf.
func (p *LevelFormatPart) Format(r *Record, buf *bytes.Buffer) {
	buf.WriteByte(levelNames[int(r.level)])
}

// TimeFormatPart is a FormatPart of the time placeholder.
type TimeFormatPart struct{}

// Format writes the time string of the record to the buf.
func (p *TimeFormatPart) Format(r *Record, buf *bytes.Buffer) {
	if r.time == "" {
		hour, min, sec := r.tm.Clock()
		buf.Write(uint2Bytes2(hour))
		buf.WriteByte(':')
		buf.Write(uint2Bytes2(min))
		buf.WriteByte(':')
		buf.Write(uint2Bytes2(sec))
	} else {
		buf.WriteString(r.time)
	}
}

// DateFormatPart is a FormatPart of the date placeholder.
type DateFormatPart struct{}

// Format writes the date string of the record to the buf.
func (p *DateFormatPart) Format(r *Record, buf *bytes.Buffer) {
	if r.date == "" {
		year, mon, day := r.tm.Date()
		buf.Write(uint2Bytes4(year))
		buf.WriteByte('-')
		buf.Write(uint2Bytes2(int(mon)))
		buf.WriteByte('-')
		buf.Write(uint2Bytes2(day))
	} else {
		buf.WriteString(r.date)
	}
}

// SourceFormatPart is a FormatPart of the source code placeholder.
type SourceFormatPart struct{}

// Format writes the source file name and line number of the record to the buf.
func (p *SourceFormatPart) Format(r *Record, buf *bytes.Buffer) {
	if r.line > 0 {
		length := len(r.file)
		if length > 0 {
			start := 0
			end := length
			for i := length - 1; i >= 0; i-- {
				c := r.file[i]
				if os.IsPathSeparator(c) {
					start = i + 1
					break
				} else if c == '.' {
					end = i
				}
			}
			buf.WriteString(r.file[start:end])
			buf.WriteByte(':')
			buf.Write(fastUint2DynamicBytes(r.line))
			return
		}
	}
	buf.Write(unknownFile)
}

// FullSourceFormatPart is a FormatPart of the full source code placeholder.
type FullSourceFormatPart struct{}

// Format writes the source file path and line number of the record to the buf.
func (p *FullSourceFormatPart) Format(r *Record, buf *bytes.Buffer) {
	if r.line > 0 {
		buf.WriteString(r.file)
		buf.WriteByte(':')
		buf.Write(fastUint2DynamicBytes(r.line))
	} else {
		buf.Write(unknownFile)
	}
}

// MessageFormatPart is a FormatPart of the message placeholder.
type MessageFormatPart struct{}

// Format writes the formatted message with args to the buf.
func (p *MessageFormatPart) Format(r *Record, buf *bytes.Buffer) {
	if len(r.args) > 0 {
		if r.message == "" {
			fmt.Fprint(buf, r.args...)
		} else {
			fmt.Fprintf(buf, r.message, r.args...)
		}
	} else if r.message != "" {
		buf.WriteString(r.message)
	}
}