// 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"
	"io"
	"math"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"time"

	"github.com/DeRuina/timberjack"
	"github.com/dustin/go-humanize"

	"github.com/caddyserver/caddy/v2"
	"github.com/caddyserver/caddy/v2/caddyconfig/caddyfile"
)

func init() {
	caddy.RegisterModule(FileWriter{})
}

// fileMode is a string made of 1 to 4 octal digits representing
// a numeric mode as specified with the `chmod` unix command.
// `"0777"` and `"777"` are thus equivalent values.
type fileMode os.FileMode

// UnmarshalJSON satisfies json.Unmarshaler.
func (m *fileMode) UnmarshalJSON(b []byte) error {
	if len(b) == 0 {
		return io.EOF
	}

	var s string
	if err := json.Unmarshal(b, &s); err != nil {
		return err
	}

	mode, err := parseFileMode(s)
	if err != nil {
		return err
	}

	*m = fileMode(mode)
	return err
}

// MarshalJSON satisfies json.Marshaler.
func (m *fileMode) MarshalJSON() ([]byte, error) {
	return fmt.Appendf(nil, "\"%04o\"", *m), nil
}

// parseFileMode parses a file mode string,
// adding support for `chmod` unix command like
// 1 to 4 digital octal values.
func parseFileMode(s string) (os.FileMode, error) {
	modeStr := fmt.Sprintf("%04s", s)
	mode, err := strconv.ParseUint(modeStr, 8, 32)
	if err != nil {
		return 0, err
	}
	return os.FileMode(mode), nil
}

// FileWriter can write logs to files. By default, log files
// are rotated ("rolled") when they get large, and old log
// files get deleted, to ensure that the process does not
// exhaust disk space.
type FileWriter struct {
	// Filename is the name of the file to write.
	Filename string `json:"filename,omitempty"`

	// The file permissions mode.
	// 0600 by default.
	Mode fileMode `json:"mode,omitempty"`

	// DirMode controls permissions for any directories created to reach Filename.
	// Default: 0700 (current behavior).
	//
	// Special values:
	//   - "inherit"   → copy the nearest existing parent directory's perms (with r→x normalization)
	//   - "from_file" → derive from the file Mode (with r→x), e.g. 0644 → 0755, 0600 → 0700
	// Numeric octal strings (e.g. "0755") are also accepted. Subject to process umask.
	DirMode string `json:"dir_mode,omitempty"`

	// Roll toggles log rolling or rotation, which is
	// enabled by default.
	Roll *bool `json:"roll,omitempty"`

	// When a log file reaches approximately this size,
	// it will be rotated.
	RollSizeMB int `json:"roll_size_mb,omitempty"`

	// Roll log file after some time
	RollInterval time.Duration `json:"roll_interval,omitempty"`

	// Roll log file at fix minutes
	// For example []int{0, 30} will roll file at xx:00 and xx:30 each hour
	// Invalid value are ignored with a warning on stderr
	// See https://github.com/DeRuina/timberjack#%EF%B8%8F-rotation-notes--warnings for caveats
	RollAtMinutes []int `json:"roll_minutes,omitempty"`

	// Roll log file at fix time
	// For example []string{"00:00", "12:00"} will roll file at 00:00 and 12:00 each day
	// Invalid value are ignored with a warning on stderr
	// See https://github.com/DeRuina/timberjack#%EF%B8%8F-rotation-notes--warnings for caveats
	RollAt []string `json:"roll_at,omitempty"`

	// Whether to compress rolled files.
	// Default: true.
	// Deprecated: Use RollCompression instead, setting it to "none".
	RollCompress *bool `json:"roll_gzip,omitempty"`

	// RollCompression selects the compression algorithm for rolled files.
	// Accepted values: "none", "gzip", "zstd".
	// Default: gzip
	RollCompression string `json:"roll_compression,omitempty"`

	// Whether to use local timestamps in rolled filenames.
	// Default: false
	RollLocalTime bool `json:"roll_local_time,omitempty"`

	// The maximum number of rolled log files to keep.
	// Default: 10
	RollKeep int `json:"roll_keep,omitempty"`

	// How many days to keep rolled log files. Default: 90
	RollKeepDays int `json:"roll_keep_days,omitempty"`

	// Rotated file will have format <logfilename>-<format>-<criterion>.log
	// Optional. If unset or invalid, defaults to 2006-01-02T15-04-05.000 (with fallback warning)
	// <format> must be a Go time compatible format, see https://pkg.go.dev/time#pkg-constants
	BackupTimeFormat string `json:"backup_time_format,omitempty"`
}

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

// Provision sets up the module
func (fw *FileWriter) Provision(ctx caddy.Context) error {
	// Replace placeholder in filename
	repl := caddy.NewReplacer()
	filename, err := repl.ReplaceOrErr(fw.Filename, true, true)
	if err != nil {
		return fmt.Errorf("invalid filename for log file: %v", err)
	}

	fw.Filename = filename
	return nil
}

func (fw FileWriter) String() string {
	fpath, err := caddy.FastAbs(fw.Filename)
	if err == nil {
		return fpath
	}
	return fw.Filename
}

// WriterKey returns a unique key representing this fw.
func (fw FileWriter) WriterKey() string {
	return "file:" + fw.Filename
}

// OpenWriter opens a new file writer.
func (fw FileWriter) OpenWriter() (io.WriteCloser, error) {
	modeIfCreating := os.FileMode(fw.Mode)
	if modeIfCreating == 0 {
		modeIfCreating = 0o600
	}

	// roll log files as a sensible default to avoid disk space exhaustion
	roll := fw.Roll == nil || *fw.Roll

	// Ensure directory exists before opening the file.
	dirPath := filepath.Dir(fw.Filename)
	switch strings.ToLower(strings.TrimSpace(fw.DirMode)) {
	case "", "0":
		// Preserve current behavior: locked-down directories by default.
		if err := os.MkdirAll(dirPath, 0o700); err != nil {
			return nil, err
		}
	case "inherit":
		if err := mkdirAllInherit(dirPath); err != nil {
			return nil, err
		}
	case "from_file":
		if err := mkdirAllFromFile(dirPath, os.FileMode(fw.Mode)); err != nil {
			return nil, err
		}
	default:
		dm, err := parseFileMode(fw.DirMode)
		if err != nil {
			return nil, fmt.Errorf("dir_mode: %w", err)
		}
		if err := os.MkdirAll(dirPath, dm); err != nil {
			return nil, err
		}
	}

	// create/open the file
	file, err := os.OpenFile(fw.Filename, os.O_WRONLY|os.O_APPEND|os.O_CREATE, modeIfCreating)
	if err != nil {
		return nil, err
	}
	info, err := file.Stat()
	if roll {
		file.Close() // timberjack will reopen it on its own
	}

	// Ensure already existing files have the right mode, since OpenFile will not set the mode in such case.
	if configuredMode := os.FileMode(fw.Mode); configuredMode != 0 {
		if err != nil {
			return nil, fmt.Errorf("unable to stat log file to see if we need to set permissions: %v", err)
		}
		// only chmod if the configured mode is different
		if info.Mode()&os.ModePerm != configuredMode&os.ModePerm {
			if err = os.Chmod(fw.Filename, configuredMode); err != nil {
				return nil, err
			}
		}
	}

	// if not rolling, then the plain file handle is all we need
	if !roll {
		return file, nil
	}

	// otherwise, return a rolling log
	if fw.RollSizeMB == 0 {
		fw.RollSizeMB = 100
	}
	if fw.RollCompress == nil {
		compress := true
		fw.RollCompress = &compress
	}
	if fw.RollKeep == 0 {
		fw.RollKeep = 10
	}
	if fw.RollKeepDays == 0 {
		fw.RollKeepDays = 90
	}

	// Determine compression algorithm to use. Priority:
	// 1) explicit RollCompression (none|gzip|zstd)
	// 2) if RollCompress is unset or true -> gzip
	// 3) if RollCompress is false -> none
	var compression string
	if fw.RollCompression != "" {
		compression = strings.ToLower(strings.TrimSpace(fw.RollCompression))
		if compression != "none" && compression != "gzip" && compression != "zstd" {
			return nil, fmt.Errorf("invalid roll_compression: %s", fw.RollCompression)
		}
	} else {
		if fw.RollCompress == nil || *fw.RollCompress {
			compression = "gzip"
		} else {
			compression = "none"
		}
	}

	return &timberjack.Logger{
		Filename:         fw.Filename,
		MaxSize:          fw.RollSizeMB,
		MaxAge:           fw.RollKeepDays,
		MaxBackups:       fw.RollKeep,
		LocalTime:        fw.RollLocalTime,
		Compression:      compression,
		RotationInterval: fw.RollInterval,
		RotateAtMinutes:  fw.RollAtMinutes,
		RotateAt:         fw.RollAt,
		BackupTimeFormat: fw.BackupTimeFormat,
		FileMode:         os.FileMode(fw.Mode),
	}, nil
}

// normalizeDirPerm ensures that read bits also have execute bits set.
func normalizeDirPerm(p os.FileMode) os.FileMode {
	if p&0o400 != 0 {
		p |= 0o100
	}
	if p&0o040 != 0 {
		p |= 0o010
	}
	if p&0o004 != 0 {
		p |= 0o001
	}
	return p
}

// mkdirAllInherit creates missing dirs using the nearest existing parent's
// permissions, normalized with r→x.
func mkdirAllInherit(dir string) error {
	if fi, err := os.Stat(dir); err == nil && fi.IsDir() {
		return nil
	}
	cur := dir
	var parent string
	for {
		next := filepath.Dir(cur)
		if next == cur {
			parent = next
			break
		}
		if fi, err := os.Stat(next); err == nil {
			if !fi.IsDir() {
				return fmt.Errorf("path component %s exists and is not a directory", next)
			}
			parent = next
			break
		}
		cur = next
	}
	perm := os.FileMode(0o700)
	if fi, err := os.Stat(parent); err == nil && fi.IsDir() {
		perm = fi.Mode().Perm()
	}
	perm = normalizeDirPerm(perm)
	return os.MkdirAll(dir, perm)
}

// mkdirAllFromFile creates missing dirs using the file's mode (with r→x) so
// 0644 → 0755, 0600 → 0700, etc.
func mkdirAllFromFile(dir string, fileMode os.FileMode) error {
	if fi, err := os.Stat(dir); err == nil && fi.IsDir() {
		return nil
	}
	perm := normalizeDirPerm(fileMode.Perm()) | 0o200 // ensure owner write on dir so files can be created
	return os.MkdirAll(dir, perm)
}

// UnmarshalCaddyfile sets up the module from Caddyfile tokens. Syntax:
//
//	file <filename> {
//	    mode          <mode>
//	    dir_mode      <mode|inherit|from_file>
//	    roll_disabled
//	    roll_size     <size>
//	    roll_uncompressed
//	    roll_compression <none|gzip|zstd>
//	    roll_local_time
//	    roll_keep     <num>
//	    roll_keep_for <days>
//	}
//
// The roll_size value has megabyte resolution.
// Fractional values are rounded up to the next whole megabyte (MiB).
//
// By default, compression is enabled, but can be turned off by setting
// the roll_uncompressed option.
//
// The roll_keep_for duration has day resolution.
// Fractional values are rounded up to the next whole number of days.
//
// If any of the mode, roll_size, roll_keep, or roll_keep_for subdirectives are
// omitted or set to a zero value, then Caddy's default value for that
// subdirective is used.
func (fw *FileWriter) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
	d.Next() // consume writer name
	if !d.NextArg() {
		return d.ArgErr()
	}
	fw.Filename = d.Val()
	if d.NextArg() {
		return d.ArgErr()
	}

	for d.NextBlock(0) {
		switch d.Val() {
		case "mode":
			var modeStr string
			if !d.AllArgs(&modeStr) {
				return d.ArgErr()
			}
			mode, err := parseFileMode(modeStr)
			if err != nil {
				return d.Errf("parsing mode: %v", err)
			}
			fw.Mode = fileMode(mode)

		case "dir_mode":
			var val string
			if !d.AllArgs(&val) {
				return d.ArgErr()
			}
			val = strings.TrimSpace(val)
			switch strings.ToLower(val) {
			case "inherit", "from_file":
				fw.DirMode = val
			default:
				if _, err := parseFileMode(val); err != nil {
					return d.Errf("parsing dir_mode: %v", err)
				}
				fw.DirMode = val
			}

		case "roll_disabled":
			var f bool
			fw.Roll = &f
			if d.NextArg() {
				return d.ArgErr()
			}

		case "roll_size":
			var sizeStr string
			if !d.AllArgs(&sizeStr) {
				return d.ArgErr()
			}
			size, err := humanize.ParseBytes(sizeStr)
			if err != nil {
				return d.Errf("parsing size: %v", err)
			}
			fw.RollSizeMB = int(math.Ceil(float64(size) / humanize.MiByte))

		case "roll_uncompressed":
			var f bool
			fw.RollCompress = &f
			if d.NextArg() {
				return d.ArgErr()
			}

		case "roll_compression":
			var comp string
			if !d.AllArgs(&comp) {
				return d.ArgErr()
			}
			comp = strings.ToLower(strings.TrimSpace(comp))
			switch comp {
			case "none", "gzip", "zstd":
				fw.RollCompression = comp
			default:
				return d.Errf("parsing roll_compression: must be 'none', 'gzip' or 'zstd'")
			}

		case "roll_local_time":
			fw.RollLocalTime = true
			if d.NextArg() {
				return d.ArgErr()
			}

		case "roll_keep":
			var keepStr string
			if !d.AllArgs(&keepStr) {
				return d.ArgErr()
			}
			keep, err := strconv.Atoi(keepStr)
			if err != nil {
				return d.Errf("parsing roll_keep number: %v", err)
			}
			fw.RollKeep = keep

		case "roll_keep_for":
			var keepForStr string
			if !d.AllArgs(&keepForStr) {
				return d.ArgErr()
			}
			keepFor, err := caddy.ParseDuration(keepForStr)
			if err != nil {
				return d.Errf("parsing roll_keep_for duration: %v", err)
			}
			if keepFor < 0 {
				return d.Errf("negative roll_keep_for duration: %v", keepFor)
			}
			fw.RollKeepDays = int(math.Ceil(keepFor.Hours() / 24))

		case "roll_interval":
			var durationStr string
			if !d.AllArgs(&durationStr) {
				return d.ArgErr()
			}
			duration, err := time.ParseDuration(durationStr)
			if err != nil {
				return d.Errf("parsing roll_interval duration: %v", err)
			}
			fw.RollInterval = duration

		case "roll_minutes":
			// Accept either a single comma-separated argument or
			// multiple space-separated arguments. Collect all
			// remaining args on the line and split on commas.
			args := d.RemainingArgs()
			if len(args) == 0 {
				return d.ArgErr()
			}
			var minutes []int
			for _, arg := range args {
				parts := strings.SplitSeq(arg, ",")
				for p := range parts {
					ms := strings.TrimSpace(p)
					if ms == "" {
						return d.Errf("parsing roll_minutes: empty value")
					}
					m, err := strconv.Atoi(ms)
					if err != nil {
						return d.Errf("parsing roll_minutes number: %v", err)
					}
					minutes = append(minutes, m)
				}
			}
			fw.RollAtMinutes = minutes

		case "roll_at":
			// Accept either a single comma-separated argument or
			// multiple space-separated arguments. Collect all
			// remaining args on the line and split on commas.
			args := d.RemainingArgs()
			if len(args) == 0 {
				return d.ArgErr()
			}
			var times []string
			for _, arg := range args {
				parts := strings.SplitSeq(arg, ",")
				for p := range parts {
					ts := strings.TrimSpace(p)
					if ts == "" {
						return d.Errf("parsing roll_at: empty value")
					}
					times = append(times, ts)
				}
			}
			fw.RollAt = times

		case "backup_time_format":
			var format string
			if !d.AllArgs(&format) {
				return d.ArgErr()
			}
			fw.BackupTimeFormat = format

		default:
			return d.Errf("unrecognized subdirective '%s'", d.Val())
		}
	}
	return nil
}

// Interface guards
var (
	_ caddy.Provisioner     = (*FileWriter)(nil)
	_ caddy.WriterOpener    = (*FileWriter)(nil)
	_ caddyfile.Unmarshaler = (*FileWriter)(nil)
)