// Copyright 2015 Matthew Holt and The Caddy Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

package logging

import (
	"encoding/json"
	"fmt"
	"strings"
	"time"

	"github.com/caddyserver/caddy/v2"
	zaplogfmt "github.com/jsternberg/zap-logfmt"
	"go.uber.org/zap"
	"go.uber.org/zap/buffer"
	"go.uber.org/zap/zapcore"
)

func init() {
	caddy.RegisterModule(ConsoleEncoder{})
	caddy.RegisterModule(JSONEncoder{})
	caddy.RegisterModule(LogfmtEncoder{})
	caddy.RegisterModule(StringEncoder{})
}

// ConsoleEncoder encodes log entries that are mostly human-readable.
type ConsoleEncoder struct {
	zapcore.Encoder
	LogEncoderConfig
}

// CaddyModule returns the Caddy module information.
func (ConsoleEncoder) CaddyModule() caddy.ModuleInfo {
	return caddy.ModuleInfo{
		ID:  "caddy.logging.encoders.console",
		New: func() caddy.Module { return new(ConsoleEncoder) },
	}
}

// Provision sets up the encoder.
func (ce *ConsoleEncoder) Provision(_ caddy.Context) error {
	ce.Encoder = zapcore.NewConsoleEncoder(ce.ZapcoreEncoderConfig())
	return nil
}

// JSONEncoder encodes entries as JSON.
type JSONEncoder struct {
	zapcore.Encoder
	*LogEncoderConfig
}

// CaddyModule returns the Caddy module information.
func (JSONEncoder) CaddyModule() caddy.ModuleInfo {
	return caddy.ModuleInfo{
		ID:  "caddy.logging.encoders.json",
		New: func() caddy.Module { return new(JSONEncoder) },
	}
}

// Provision sets up the encoder.
func (je *JSONEncoder) Provision(_ caddy.Context) error {
	je.Encoder = zapcore.NewJSONEncoder(je.ZapcoreEncoderConfig())
	return nil
}

// LogfmtEncoder encodes log entries as logfmt:
// https://www.brandur.org/logfmt
type LogfmtEncoder struct {
	zapcore.Encoder
	LogEncoderConfig
}

// CaddyModule returns the Caddy module information.
func (LogfmtEncoder) CaddyModule() caddy.ModuleInfo {
	return caddy.ModuleInfo{
		ID:  "caddy.logging.encoders.logfmt",
		New: func() caddy.Module { return new(LogfmtEncoder) },
	}
}

// Provision sets up the encoder.
func (lfe *LogfmtEncoder) Provision(_ caddy.Context) error {
	lfe.Encoder = zaplogfmt.NewEncoder(lfe.ZapcoreEncoderConfig())
	return nil
}

// StringEncoder writes a log entry that consists entirely
// of a single string field in the log entry. This is useful
// for custom, self-encoded log entries that consist of a
// single field in the structured log entry.
type StringEncoder struct {
	zapcore.Encoder
	FieldName   string          `json:"field,omitempty"`
	FallbackRaw json.RawMessage `json:"fallback,omitempty" caddy:"namespace=caddy.logging.encoders inline_key=format"`
}

// CaddyModule returns the Caddy module information.
func (StringEncoder) CaddyModule() caddy.ModuleInfo {
	return caddy.ModuleInfo{
		ID:  "caddy.logging.encoders.string",
		New: func() caddy.Module { return new(StringEncoder) },
	}
}

// Provision sets up the encoder.
func (se *StringEncoder) Provision(ctx caddy.Context) error {
	if se.FallbackRaw != nil {
		val, err := ctx.LoadModule(se, "FallbackRaw")
		if err != nil {
			return fmt.Errorf("loading fallback encoder module: %v", err)
		}
		se.Encoder = val.(zapcore.Encoder)
	}
	if se.Encoder == nil {
		se.Encoder = nopEncoder{}
	}
	return nil
}

// Clone wraps the underlying encoder's Clone. This is
// necessary because we implement our own EncodeEntry,
// and if we simply let the embedded encoder's Clone
// be promoted, it would return a clone of that, and
// we'd lose our StringEncoder's EncodeEntry.
func (se StringEncoder) Clone() zapcore.Encoder {
	return StringEncoder{
		Encoder:   se.Encoder.Clone(),
		FieldName: se.FieldName,
	}
}

// EncodeEntry partially implements the zapcore.Encoder interface.
func (se StringEncoder) EncodeEntry(ent zapcore.Entry, fields []zapcore.Field) (*buffer.Buffer, error) {
	for _, f := range fields {
		if f.Key == se.FieldName {
			buf := bufferpool.Get()
			buf.AppendString(f.String)
			if !strings.HasSuffix(f.String, "\n") {
				buf.AppendByte('\n')
			}
			return buf, nil
		}
	}
	if se.Encoder == nil {
		return nil, fmt.Errorf("no fallback encoder defined")
	}
	return se.Encoder.EncodeEntry(ent, fields)
}

// LogEncoderConfig holds configuration common to most encoders.
type LogEncoderConfig struct {
	MessageKey     *string `json:"message_key,omitempty"`
	LevelKey       *string `json:"level_key,omitempty"`
	TimeKey        *string `json:"time_key,omitempty"`
	NameKey        *string `json:"name_key,omitempty"`
	CallerKey      *string `json:"caller_key,omitempty"`
	StacktraceKey  *string `json:"stacktrace_key,omitempty"`
	LineEnding     *string `json:"line_ending,omitempty"`
	TimeFormat     string  `json:"time_format,omitempty"`
	DurationFormat string  `json:"duration_format,omitempty"`
	LevelFormat    string  `json:"level_format,omitempty"`
}

// ZapcoreEncoderConfig returns the equivalent zapcore.EncoderConfig.
// If lec is nil, zap.NewProductionEncoderConfig() is returned.
func (lec *LogEncoderConfig) ZapcoreEncoderConfig() zapcore.EncoderConfig {
	cfg := zap.NewProductionEncoderConfig()
	if lec == nil {
		lec = new(LogEncoderConfig)
	}
	if lec.MessageKey != nil {
		cfg.MessageKey = *lec.MessageKey
	}
	if lec.TimeKey != nil {
		cfg.TimeKey = *lec.TimeKey
	}
	if lec.NameKey != nil {
		cfg.NameKey = *lec.NameKey
	}
	if lec.CallerKey != nil {
		cfg.CallerKey = *lec.CallerKey
	}
	if lec.StacktraceKey != nil {
		cfg.StacktraceKey = *lec.StacktraceKey
	}
	if lec.LineEnding != nil {
		cfg.LineEnding = *lec.LineEnding
	}

	// time format
	var timeFormatter zapcore.TimeEncoder
	switch lec.TimeFormat {
	case "", "unix_seconds_float":
		timeFormatter = zapcore.EpochTimeEncoder
	case "unix_milli_float":
		timeFormatter = zapcore.EpochMillisTimeEncoder
	case "unix_nano":
		timeFormatter = zapcore.EpochNanosTimeEncoder
	case "iso8601":
		timeFormatter = zapcore.ISO8601TimeEncoder
	default:
		timeFormat := lec.TimeFormat
		switch lec.TimeFormat {
		case "rfc3339":
			timeFormat = time.RFC3339
		case "rfc3339_nano":
			timeFormat = time.RFC3339Nano
		case "wall":
			timeFormat = "2006/01/02 15:04:05"
		case "wall_milli":
			timeFormat = "2006/01/02 15:04:05.000"
		case "wall_nano":
			timeFormat = "2006/01/02 15:04:05.000000000"
		}
		timeFormatter = func(ts time.Time, encoder zapcore.PrimitiveArrayEncoder) {
			encoder.AppendString(ts.UTC().Format(timeFormat))
		}
	}
	cfg.EncodeTime = timeFormatter

	// duration format
	var durFormatter zapcore.DurationEncoder
	switch lec.DurationFormat {
	case "", "seconds":
		durFormatter = zapcore.SecondsDurationEncoder
	case "nano":
		durFormatter = zapcore.NanosDurationEncoder
	case "string":
		durFormatter = zapcore.StringDurationEncoder
	}
	cfg.EncodeDuration = durFormatter

	// level format
	var levelFormatter zapcore.LevelEncoder
	switch lec.LevelFormat {
	case "", "lower":
		levelFormatter = zapcore.LowercaseLevelEncoder
	case "upper":
		levelFormatter = zapcore.CapitalLevelEncoder
	case "color":
		levelFormatter = zapcore.CapitalColorLevelEncoder
	}
	cfg.EncodeLevel = levelFormatter

	return cfg
}

var bufferpool = buffer.NewPool()

// Interface guards
var (
	_ zapcore.Encoder = (*ConsoleEncoder)(nil)
	_ zapcore.Encoder = (*JSONEncoder)(nil)
	_ zapcore.Encoder = (*LogfmtEncoder)(nil)
	_ zapcore.Encoder = (*StringEncoder)(nil)
)