package storage

import (
	"context"
	"fmt"
	"io"
	"os"
	"path/filepath"
)

type Disk struct {
	root string
}

func NewDisk(root string) (*Disk, error) {
	if root == "" {
		return nil, fmt.Errorf("storage: disk backend requires a directory")
	}
	if err := os.MkdirAll(root, 0o755); err != nil {
		return nil, fmt.Errorf("storage: create disk root: %w", err)
	}
	return &Disk{root: filepath.Clean(root)}, nil
}

func (d *Disk) path(key string) (string, error) {
	if err := ValidateKey(key); err != nil {
		return "", err
	}
	return filepath.Join(d.root, filepath.FromSlash(key)), nil
}

func (d *Disk) Get(_ context.Context, key string) (io.ReadCloser, error) {
	p, err := d.path(key)
	if err != nil {
		return nil, err
	}
	f, err := os.Open(p)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, ErrNotExist
		}
		return nil, fmt.Errorf("storage: get %q: %w", key, err)
	}
	return f, nil
}

func (d *Disk) Put(_ context.Context, key string, r io.Reader) error {
	p, err := d.path(key)
	if err != nil {
		return err
	}
	if err := os.MkdirAll(filepath.Dir(p), 0o755); err != nil {
		return fmt.Errorf("storage: put %q: %w", key, err)
	}
	// dont let readers see a partial object
	tmp, err := os.CreateTemp(filepath.Dir(p), ".tmp-*")
	if err != nil {
		return fmt.Errorf("storage: put %q: %w", key, err)
	}
	tmpName := tmp.Name()
	defer os.Remove(tmpName)
	if _, err := io.Copy(tmp, r); err != nil {
		_ = tmp.Close()
		return fmt.Errorf("storage: put %q: %w", key, err)
	}
	if err := tmp.Close(); err != nil {
		return fmt.Errorf("storage: put %q: %w", key, err)
	}
	if err := os.Rename(tmpName, p); err != nil {
		return fmt.Errorf("storage: put %q: %w", key, err)
	}
	return nil
}

func (d *Disk) Delete(_ context.Context, key string) error {
	p, err := d.path(key)
	if err != nil {
		return err
	}
	if err := os.Remove(p); err != nil {
		if os.IsNotExist(err) {
			return nil
		}
		return fmt.Errorf("storage: delete %q: %w", key, err)
	}
	return nil
}