package starlog

import (
	"errors"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"sync"
	"time"
)

var ErrRotatingFileSinkClosed = errors.New("rotating file sink closed")

type RotatingFileSink struct {
	mu            sync.Mutex
	path          string
	policy        RotatePolicy
	checkInterval time.Duration
	options       RotateManageOptions
	appendMode    bool

	file      *os.File
	lastCheck time.Time
	closed    bool
}

func normalizeRotateCheckInterval(interval time.Duration) time.Duration {
	if interval <= 0 {
		return time.Second
	}
	return interval
}

func ensureLogDir(path string) error {
	dir := filepath.Dir(path)
	if dir == "" || dir == "." {
		return nil
	}
	return os.MkdirAll(dir, 0755)
}

func newRotatePolicySink(path string, appendMode bool, policy RotatePolicy, checkInterval time.Duration, options RotateManageOptions) (*RotatingFileSink, error) {
	if policy == nil {
		return nil, errors.New("rotate policy is nil")
	}
	fullpath, err := filepath.Abs(path)
	if err != nil {
		return nil, err
	}
	sink := &RotatingFileSink{
		path:          fullpath,
		policy:        policy,
		checkInterval: normalizeRotateCheckInterval(checkInterval),
		options:       options,
		appendMode:    appendMode,
	}
	if err = sink.openFileLocked(appendMode); err != nil {
		return nil, err
	}
	return sink, nil
}

func NewRotatePolicySink(path string, appendMode bool, policy RotatePolicy, checkInterval time.Duration) (*RotatingFileSink, error) {
	return newRotatePolicySink(path, appendMode, policy, checkInterval, RotateManageOptions{})
}

func NewManagedRotatePolicySink(path string, appendMode bool, policy RotatePolicy, checkInterval time.Duration, options RotateManageOptions) (*RotatingFileSink, error) {
	return newRotatePolicySink(path, appendMode, policy, checkInterval, options)
}

func NewRotateByTimeSink(path string, appendMode bool, interval time.Duration, checkInterval time.Duration) (*RotatingFileSink, error) {
	return NewRotatePolicySink(path, appendMode, NewRotateByTimePolicy(interval), checkInterval)
}

func NewManagedRotateByTimeSink(path string, appendMode bool, interval time.Duration, checkInterval time.Duration, options RotateManageOptions) (*RotatingFileSink, error) {
	return NewManagedRotatePolicySink(path, appendMode, NewRotateByTimePolicy(interval), checkInterval, options)
}

func NewRotateBySizeSink(path string, appendMode bool, maxSizeBytes int64, checkInterval time.Duration) (*RotatingFileSink, error) {
	return NewRotatePolicySink(path, appendMode, NewRotateBySizePolicy(maxSizeBytes), checkInterval)
}

func NewManagedRotateBySizeSink(path string, appendMode bool, maxSizeBytes int64, checkInterval time.Duration, options RotateManageOptions) (*RotatingFileSink, error) {
	return NewManagedRotatePolicySink(path, appendMode, NewRotateBySizePolicy(maxSizeBytes), checkInterval, options)
}

func NewRotateByTimeSizeSink(path string, appendMode bool, interval time.Duration, maxSizeBytes int64, checkInterval time.Duration) (*RotatingFileSink, error) {
	return NewRotatePolicySink(path, appendMode, NewRotateByTimeSizePolicy(interval, maxSizeBytes), checkInterval)
}

func NewManagedRotateByTimeSizeSink(path string, appendMode bool, interval time.Duration, maxSizeBytes int64, checkInterval time.Duration, options RotateManageOptions) (*RotatingFileSink, error) {
	return NewManagedRotatePolicySink(path, appendMode, NewRotateByTimeSizePolicy(interval, maxSizeBytes), checkInterval, options)
}

func (sink *RotatingFileSink) openFileLocked(appendMode bool) error {
	if sink == nil {
		return nil
	}
	if err := ensureLogDir(sink.path); err != nil {
		return err
	}
	flags := os.O_CREATE | os.O_WRONLY
	if appendMode {
		flags |= os.O_APPEND
	} else {
		flags |= os.O_TRUNC
	}
	fp, err := os.OpenFile(sink.path, flags, 0644)
	if err != nil {
		return err
	}
	sink.file = fp
	return nil
}

func (sink *RotatingFileSink) shouldCheckRotateLocked(now time.Time) bool {
	if sink == nil {
		return false
	}
	if sink.lastCheck.IsZero() || now.Sub(sink.lastCheck) >= sink.checkInterval {
		sink.lastCheck = now
		return true
	}
	return false
}

func (sink *RotatingFileSink) rotateIfNeededLocked(now time.Time) error {
	if sink == nil || sink.file == nil || sink.policy == nil {
		return nil
	}
	info, err := sink.file.Stat()
	if err != nil {
		return err
	}
	entry := &Entry{Time: now}
	if !sink.policy.ShouldRotate(info, entry) {
		return nil
	}
	archivePath := strings.TrimSpace(resolveRotateArchivePath(sink.policy, sink.path, now))
	if archivePath == "" || archivePath == sink.path {
		return nil
	}
	if err = ensureLogDir(archivePath); err != nil {
		return err
	}
	if err = sink.file.Close(); err != nil {
		return err
	}
	sink.file = nil
	if err = os.Rename(sink.path, archivePath); err != nil {
		reopenErr := sink.openFileLocked(true)
		if reopenErr != nil {
			return fmt.Errorf("rotate rename failed: %v; reopen failed: %w", err, reopenErr)
		}
		return err
	}
	if err = sink.openFileLocked(false); err != nil {
		return err
	}
	if err = ApplyRotateManageOptions(archivePath, sink.path, sink.options); err != nil {
		return err
	}
	return nil
}

func (sink *RotatingFileSink) Write(data []byte) error {
	if sink == nil {
		return nil
	}
	sink.mu.Lock()
	defer sink.mu.Unlock()
	if sink.closed {
		return ErrRotatingFileSinkClosed
	}
	if sink.file == nil {
		if err := sink.openFileLocked(true); err != nil {
			return err
		}
	}
	now := time.Now()
	if sink.shouldCheckRotateLocked(now) {
		if err := sink.rotateIfNeededLocked(now); err != nil {
			return err
		}
	}
	_, err := sink.file.Write(data)
	return err
}

func (sink *RotatingFileSink) Sync() error {
	if sink == nil {
		return nil
	}
	sink.mu.Lock()
	defer sink.mu.Unlock()
	if sink.file == nil {
		return nil
	}
	return sink.file.Sync()
}

func (sink *RotatingFileSink) Close() error {
	if sink == nil {
		return nil
	}
	sink.mu.Lock()
	defer sink.mu.Unlock()
	if sink.closed {
		return nil
	}
	sink.closed = true
	if sink.file == nil {
		return nil
	}
	err := sink.file.Close()
	sink.file = nil
	return err
}

func (sink *RotatingFileSink) Path() string {
	if sink == nil {
		return ""
	}
	sink.mu.Lock()
	defer sink.mu.Unlock()
	return sink.path
}