package local

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"errors"
	"fmt"
	"io"
	"os"
	"path/filepath"
	"strings"

	"git.apinb.com/ops/files/internal/storage"
)

func (c *Client) Open(ctx context.Context, objectKey string, byteRange *storage.ByteRange) (io.ReadCloser, error) {
	path, err := c.resolveObjectPath(objectKey)
	if err != nil {
		return nil, err
	}
	file, err := os.Open(path)
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return nil, storage.ErrObjectNotFound
		}
		return nil, fmt.Errorf("打开本地文件: %w", err)
	}
	if byteRange == nil {
		return &contextReadCloser{ctx: ctx, reader: file, closer: file}, nil
	}
	info, err := file.Stat()
	if err != nil {
		_ = file.Close()
		return nil, err
	}
	if byteRange.Start < 0 || byteRange.End < byteRange.Start || byteRange.End >= info.Size() {
		_ = file.Close()
		return nil, fmt.Errorf("文件读取范围无效")
	}
	if _, err := file.Seek(byteRange.Start, io.SeekStart); err != nil {
		_ = file.Close()
		return nil, err
	}
	return &contextReadCloser{ctx: ctx, reader: io.LimitReader(file, byteRange.Length()), closer: file}, nil
}

func (c *Client) Stat(ctx context.Context, objectKey string) (storage.ObjectInfo, error) {
	path, err := c.resolveObjectPath(objectKey)
	if err != nil {
		return storage.ObjectInfo{}, err
	}
	file, err := os.Open(path)
	if err != nil {
		if errors.Is(err, os.ErrNotExist) {
			return storage.ObjectInfo{}, storage.ErrObjectNotFound
		}
		return storage.ObjectInfo{}, fmt.Errorf("打开本地文件: %w", err)
	}
	defer file.Close()
	info, err := file.Stat()
	if err != nil {
		return storage.ObjectInfo{}, err
	}
	hasher := sha256.New()
	if _, err := io.Copy(hasher, &contextReader{ctx: ctx, reader: file}); err != nil {
		return storage.ObjectInfo{}, fmt.Errorf("计算本地文件摘要: %w", err)
	}
	return storage.ObjectInfo{
		Size:         info.Size(),
		StorageETag:  "sha256:" + hex.EncodeToString(hasher.Sum(nil)),
		LastModified: info.ModTime().UTC(),
	}, nil
}

func (c *Client) Delete(_ context.Context, objectKey string) error {
	path, err := c.resolveObjectPath(objectKey)
	if err != nil {
		return err
	}
	if err := os.Remove(path); err != nil && !os.IsNotExist(err) {
		return fmt.Errorf("删除本地文件: %w", err)
	}
	c.removeEmptyParents(filepath.Dir(path))
	return nil
}

func (c *Client) removeEmptyParents(directory string) {
	boundary := filepath.Clean(c.objectsPath)
	for current := filepath.Clean(directory); current != boundary; current = filepath.Dir(current) {
		relative, err := filepath.Rel(boundary, current)
		if err != nil || relative == ".." || strings.HasPrefix(relative, ".."+string(filepath.Separator)) {
			return
		}
		if err := os.Remove(current); err != nil {
			return
		}
	}
}

func (c *Client) Status(_ context.Context) (storage.RuntimeStatus, error) {
	diskStatus, err := c.diskStatus()
	if err != nil {
		return storage.RuntimeStatus{Provider: c.Provider(), Container: c.Container()}, err
	}
	probe, err := os.CreateTemp(c.stagingPath, ".write-probe-")
	if err != nil {
		return storage.RuntimeStatus{Provider: c.Provider(), Container: c.Container(), Disk: diskStatus}, fmt.Errorf("本地存储目录不可写: %w", err)
	}
	probePath := probe.Name()
	removeProbe := func() { _ = os.Remove(probePath) }
	defer removeProbe()
	if err := probe.Chmod(0o640); err != nil {
		_ = probe.Close()
		return storage.RuntimeStatus{Provider: c.Provider(), Container: c.Container(), Disk: diskStatus}, err
	}
	if _, err := probe.Write([]byte("files-storage-probe")); err != nil {
		_ = probe.Close()
		return storage.RuntimeStatus{Provider: c.Provider(), Container: c.Container(), Disk: diskStatus}, err
	}
	if err := probe.Sync(); err != nil {
		_ = probe.Close()
		return storage.RuntimeStatus{Provider: c.Provider(), Container: c.Container(), Disk: diskStatus}, err
	}
	if err := probe.Close(); err != nil {
		return storage.RuntimeStatus{Provider: c.Provider(), Container: c.Container(), Disk: diskStatus}, err
	}
	if err := os.Remove(probePath); err != nil {
		return storage.RuntimeStatus{Provider: c.Provider(), Container: c.Container(), Disk: diskStatus}, err
	}
	return storage.RuntimeStatus{
		Provider:  c.Provider(),
		Container: c.Container(),
		Writable:  diskStatus.Level != "critical",
		Disk:      diskStatus,
	}, nil
}

type contextReadCloser struct {
	ctx    context.Context
	reader io.Reader
	closer io.Closer
}

func (r *contextReadCloser) Read(buffer []byte) (int, error) {
	if err := r.ctx.Err(); err != nil {
		return 0, err
	}
	return r.reader.Read(buffer)
}

func (r *contextReadCloser) Close() error { return r.closer.Close() }