// Copyright 2015, 2016 Eris Industries (UK) Ltd.
// This file is part of Eris-RT

// Eris-RT is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.

// Eris-RT is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Eris-RT.  If not, see <http://www.gnu.org/licenses/>.

package util

import (
  "fmt"
  "io"
  "os"
)

// Ensure the directory exists or create it if needed.
func EnsureDir(dir string, mode os.FileMode) error {
  if fileOptions, err := os.Stat(dir); os.IsNotExist(err) {
    if errMake := os.MkdirAll(dir, mode); errMake != nil {
      return fmt.Errorf("Could not create directory %s. %v", dir, err)
    }
  } else if err != nil {
    return fmt.Errorf("Error asserting directory %s: %v", dir, err)
  } else if !fileOptions.IsDir() {
    return fmt.Errorf("Path already exists as a file: %s", dir)
  }
  return nil
}

// Check whether the provided directory exists
func IsDir(directory string) bool {
  fileInfo, err := os.Stat(directory)
  if err != nil {
    return false
  }
  return fileInfo.IsDir()
}

// copied from http://stackoverflow.com/questions/21060945/simple-way-to-copy-a-file-in-golang
// CopyFile copies a file from src to dst. If src and dst files exist, and are
// the same, then return success. Otherise, attempt to create a hard link
// between the two files. If that fail, copy the file contents from src to dst.
func CopyFile(src, dst string) (err error) {
    sfi, err := os.Stat(src)
    if err != nil {
        return
    }
    if !sfi.Mode().IsRegular() {
        // cannot copy non-regular files (e.g., directories,
        // symlinks, devices, etc.)
        return fmt.Errorf("CopyFile: non-regular source file %s (%q)", sfi.Name(), sfi.Mode().String())
    }
    dfi, err := os.Stat(dst)
    if err != nil {
        if !os.IsNotExist(err) {
            return
        }
    } else {
        if !(dfi.Mode().IsRegular()) {
            return fmt.Errorf("CopyFile: non-regular destination file %s (%q)", dfi.Name(), dfi.Mode().String())
        }
        if os.SameFile(sfi, dfi) {
            return
        }
    }
    // NOTE: [ben] we do not want to create a hard link currently
    // if err = os.Link(src, dst); err == nil {
    //     return
    // }
    err = copyFileContents(src, dst)
    return
}

// copyFileContents copies the contents of the file named src to the file named
// by dst. The file will be created if it does not already exist. If the
// destination file exists, all its contents will be replaced by the contents
// of the source file.
func copyFileContents(src, dst string) (err error) {
    in, err := os.Open(src)
    if err != nil {
        return
    }
    defer in.Close()
    out, err := os.Create(dst)
    if err != nil {
        return
    }
    defer func() {
        cerr := out.Close()
        if err == nil {
            err = cerr
        }
    }()
    if _, err = io.Copy(out, in); err != nil {
        return
    }
    // TODO: [ben] this blocks, so copy should be put in go-routine
    err = out.Sync()
    return
}