// 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"
	"github.com/caddyserver/caddy/v2/caddyconfig/caddyfile"
	"go.uber.org/zap"
	"go.uber.org/zap/buffer"
	"go.uber.org/zap/zapcore"
)

func init() {
	caddy.RegisterModule(ConsoleEncoder{})
	caddy.RegisterModule(JSONEncoder{})
	caddy.RegisterModule(SingleFieldEncoder{})
}

// ConsoleEncoder encodes log entries that are mostly human-readable.
type ConsoleEncoder struct {
	zapcore.Encoder `json:"-"`
	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
}

// UnmarshalCaddyfile sets up the module from Caddyfile tokens. Syntax:
//
//     console {
//         <common encoder config subdirectives...>
//     }
//
// See the godoc on the LogEncoderConfig type for the syntax of
// subdirectives that are common to most/all encoders.
func (ce *ConsoleEncoder) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
	for d.Next() {
		if d.NextArg() {
			return d.ArgErr()
		}
		err := ce.LogEncoderConfig.UnmarshalCaddyfile(d)
		if err != nil {
			return err
		}
	}
	return nil
}

// JSONEncoder encodes entries as JSON.
type JSONEncoder struct {
	zapcore.Encoder `json:"-"`
	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
}

// UnmarshalCaddyfile sets up the module from Caddyfile tokens. Syntax:
//
//     json {
//         <common encoder config subdirectives...>
//     }
//
// See the godoc on the LogEncoderConfig type for the syntax of
// subdirectives that are common to most/all encoders.
func (je *JSONEncoder) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
	for d.Next() {
		if d.NextArg() {
			return d.ArgErr()
		}
		err := je.LogEncoderConfig.UnmarshalCaddyfile(d)
		if err != nil {
			return err
		}
	}
	return nil
}

// SingleFieldEncoder 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 SingleFieldEncoder struct {
	zapcore.Encoder `json:"-"`
	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 (SingleFieldEncoder) CaddyModule() caddy.ModuleInfo {
	return caddy.ModuleInfo{
		ID:  "caddy.logging.encoders.single_field",
		New: func() caddy.Module { return new(SingleFieldEncoder) },
	}
}

// Provision sets up the encoder.
func (se *SingleFieldEncoder) 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 SingleFieldEncoder's EncodeEntry.
func (se SingleFieldEncoder) Clone() zapcore.Encoder {
	return SingleFieldEncoder{
		Encoder:   se.Encoder.Clone(),
		FieldName: se.FieldName,
	}
}

// EncodeEntry partially implements the zapcore.Encoder interface.
func (se SingleFieldEncoder) 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)
}

// UnmarshalCaddyfile sets up the module from Caddyfile tokens. Syntax:
//
//     single_field <field_name>
//
func (se *SingleFieldEncoder) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
	for d.Next() {
		var fieldName string
		if !d.AllArgs(&fieldName) {
			return d.ArgErr()
		}
		se.FieldName = d.Val()
	}
	return nil
}

// 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"`
}

// UnmarshalCaddyfile populates the struct from Caddyfile tokens. Syntax:
//
//     {
//         message_key <key>
//         level_key   <key>
//         time_key    <key>
//         name_key    <key>
//         caller_key  <key>
//         stacktrace_key <key>
//         line_ending  <char>
//         time_format  <format>
//         level_format <format>
//     }
//
func (lec *LogEncoderConfig) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
	for nesting := d.Nesting(); d.NextBlock(nesting); {
		subdir := d.Val()
		var arg string
		if !d.AllArgs(&arg) {
			return d.ArgErr()
		}
		switch subdir {
		case "message_key":
			lec.MessageKey = &arg
		case "level_key":
			lec.LevelKey = &arg
		case "time_key":
			lec.TimeKey = &arg
		case "name_key":
			lec.NameKey = &arg
		case "caller_key":
			lec.CallerKey = &arg
		case "stacktrace_key":
			lec.StacktraceKey = &arg
		case "line_ending":
			lec.LineEnding = &arg
		case "time_format":
			lec.TimeFormat = arg
		case "level_format":
			lec.LevelFormat = arg
		default:
			return d.Errf("unrecognized subdirective %s", subdir)
		}
	}
	return nil
}

// 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.LevelKey != nil {
		cfg.LevelKey = *lec.LevelKey
	}
	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 = (*SingleFieldEncoder)(nil)

	_ caddyfile.Unmarshaler = (*ConsoleEncoder)(nil)
	_ caddyfile.Unmarshaler = (*JSONEncoder)(nil)
	_ caddyfile.Unmarshaler = (*SingleFieldEncoder)(nil)
)