<?php

namespace Amp\File;

use Amp\{ Coroutine, Deferred, Loop, Promise, Success };

class UvDriver implements Driver {
    /** @var \Amp\Loop\Driver */
    private $driver;

    /** @var \UVLoop|resource Loop resource of type uv_loop or instance of \UVLoop. */
    private $loop;

    /** @var string Loop onReadable watcher. */
    private $busy;

    /**
     * @param \Amp\Loop\UvDriver $driver
     */
    public function __construct(Loop\UvDriver $driver) {
        $this->driver = $driver;
        $this->loop = $driver->getHandle();

        // dummy handle to be able to tell the loop that there is work being done and it shouldn't abort if there are no other watchers at a given moment
        $this->busy = $driver->repeat(PHP_INT_MAX, function(){ });
        $driver->unreference($this->busy);
    }

    /**
     * {@inheritdoc}
     */
    public function open(string $path, string $mode): Promise {
        $flags = $this->parseMode($mode);

        $chmod = ($flags & \UV::O_CREAT) ? 0644 : 0;
        $this->driver->reference($this->busy);
        $deferred = new Deferred;
        $openArr = [$mode, $path, $deferred];
        \uv_fs_open($this->loop, $path, $flags, $chmod, function ($fh) use ($openArr) {
            if ($fh) {
                $this->onOpenHandle($fh, $openArr);
            } else {
                $this->driver->unreference($this->busy);
                list( , $path, $deferred) = $openArr;
                $deferred->fail(new FilesystemException(
                    "Failed opening file handle to $path"
                ));
            }
        });

        return $deferred->promise();
    }

    private function parseMode(string $mode): int {
        $mode = \str_replace(['b', 't'], '', $mode);

        switch ($mode) {
            case "r":  return \UV::O_RDONLY;
            case "r+": return \UV::O_RDWR;
            case "w":  return \UV::O_WRONLY | \UV::O_CREAT;
            case "w+": return \UV::O_RDWR | \UV::O_CREAT;
            case "a":  return \UV::O_WRONLY | \UV::O_CREAT | \UV::O_APPEND;
            case "a+": return \UV::O_RDWR | \UV::O_CREAT | \UV::O_APPEND;
            case "x":  return \UV::O_WRONLY | \UV::O_CREAT | \UV::O_EXCL;
            case "x+": return \UV::O_RDWR | \UV::O_CREAT | \UV::O_EXCL;
            case "c":  return \UV::O_WRONLY | \UV::O_CREAT;
            case "c+": return \UV::O_RDWR | \UV::O_CREAT;

            default:
                throw new \Error('Invalid file mode');
        }
    }

    private function onOpenHandle($fh, array $openArr) {
        list($mode) = $openArr;
        if ($mode[0] === "w") {
            \uv_fs_ftruncate($this->loop, $fh, $length = 0, function ($fh) use ($openArr) {
                $this->driver->unreference($this->busy);
                if ($fh) {
                    $this->finalizeHandle($fh, $size = 0, $openArr);
                } else {
                    list( , $path, $deferred) = $openArr;
                    $deferred->fail(new FilesystemException(
                        "Failed truncating file $path"
                    ));
                }
            });
        } else {
            \uv_fs_fstat($this->loop, $fh, function($fh, $stat) use ($openArr) {
                $this->driver->unreference($this->busy);
                if ($fh) {
                    StatCache::set($openArr[1], $stat);
                    $this->finalizeHandle($fh, $stat["size"], $openArr);
                } else {
                    list( , $path, $deferred) = $openArr;
                    $deferred->fail(new FilesystemException(
                        "Failed reading file size from open handle pointing to $path"
                    ));
                }
            });
        }
    }

    private function finalizeHandle($fh, $size, array $openArr) {
        list($mode, $path, $deferred) = $openArr;
        $handle = new UvHandle($this->driver, $this->busy, $fh, $path, $mode, $size);
        $deferred->resolve($handle);
    }

    /**
     * {@inheritdoc}
     */
    public function stat(string $path): Promise {
        if ($stat = StatCache::get($path)) {
            return new Success($stat);
        }

        $this->driver->reference($this->busy);
        $deferred = new Deferred;
        \uv_fs_stat($this->loop, $path, function($fh, $stat) use ($deferred, $path) {
            if (empty($fh)) {
                $stat = null;
            } else {
                StatCache::set($path, $stat);
            }
            $this->driver->unreference($this->busy);
            $deferred->resolve($stat);
        });

        return $deferred->promise();
    }

    /**
     * {@inheritdoc}
     */
    public function exists(string $path): Promise {
        $deferred = new Deferred;
        $this->stat($path)->onResolve(function ($error, $result) use ($deferred) {
            $deferred->resolve((bool) $result);
        });

        return $deferred->promise();
    }

    /**
     * {@inheritdoc}
     */
    public function isdir(string $path): Promise {
        $deferred = new Deferred;
        $this->stat($path)->onResolve(function ($error, $result) use ($deferred) {
            if ($result) {
                $deferred->resolve(!($result["mode"] & \UV::S_IFREG));
            } else {
                $deferred->resolve(false);
            }
        });

        return $deferred->promise();
    }

    /**
     * {@inheritdoc}
     */
    public function isfile(string $path): Promise {
        $deferred = new Deferred;
        $this->stat($path)->onResolve(function ($error, $result) use ($deferred) {
            if ($result) {
                $deferred->resolve((bool) ($result["mode"] & \UV::S_IFREG));
            } else {
                $deferred->resolve(false);
            }
        });

        return $deferred->promise();
    }

    /**
     * {@inheritdoc}
     */
    public function size(string $path): Promise {
        $deferred = new Deferred;
        $this->stat($path)->onResolve(function ($error, $result) use ($deferred) {
            if (empty($result)) {
                $deferred->fail(new FilesystemException(
                    "Specified path does not exist"
                ));
            } elseif (($result["mode"] & \UV::S_IFREG)) {
                $deferred->resolve($result["size"]);
            } else {
                $deferred->fail(new FilesystemException(
                    "Specified path is not a regular file"
                ));
            }
        });

        return $deferred->promise();
    }

    /**
     * {@inheritdoc}
     */
    public function mtime(string $path): Promise {
        $deferred = new Deferred;
        $this->stat($path)->onResolve(function ($error, $result) use ($deferred) {
            if ($result) {
                $deferred->resolve($result["mtime"]);
            } else {
                $deferred->fail(new FilesystemException(
                    "Specified path does not exist"
                ));
            }
        });

        return $deferred->promise();
    }

    /**
     * {@inheritdoc}
     */
    public function atime(string $path): Promise {
        $deferred = new Deferred;
        $this->stat($path)->onResolve(function ($error, $result) use ($deferred) {
            if ($result) {
                $deferred->resolve($result["atime"]);
            } else {
                $deferred->fail(new FilesystemException(
                    "Specified path does not exist"
                ));
            }
        });

        return $deferred->promise();
    }

    /**
     * {@inheritdoc}
     */
    public function ctime(string $path): Promise {
        $deferred = new Deferred;
        $this->stat($path)->onResolve(function ($error, $result) use ($deferred) {
            if ($result) {
                $deferred->resolve($result["ctime"]);
            } else {
                $deferred->fail(new FilesystemException(
                    "Specified path does not exist"
                ));
            }
        });

        return $deferred->promise();
    }

    /**
     * {@inheritdoc}
     */
    public function lstat(string $path): Promise {
        $this->driver->reference($this->busy);
        $deferred = new Deferred;
        \uv_fs_lstat($this->loop, $path, function($fh, $stat) use ($deferred) {
            if (empty($fh)) {
                $stat = null;
            }
            $this->driver->unreference($this->busy);
            $deferred->resolve($stat);
        });

        return $deferred->promise();
    }

    /**
     * {@inheritdoc}
     */
    public function symlink(string $target, string $link): Promise {
        $this->driver->reference($this->busy);
        $deferred = new Deferred;
        \uv_fs_symlink($this->loop, $target, $link, \UV::S_IRWXU | \UV::S_IRUSR, function ($fh) use ($deferred) {
            $this->driver->unreference($this->busy);
            $deferred->resolve((bool) $fh);
        });

        return $deferred->promise();
    }

    /**
     * {@inheritdoc}
     */
    public function link(string $target, string $link): Promise {
        $this->driver->reference($this->busy);
        $deferred = new Deferred;
        \uv_fs_link($this->loop, $target, $link, \UV::S_IRWXU | \UV::S_IRUSR, function ($fh) use ($deferred) {
            $this->driver->unreference($this->busy);
            $deferred->resolve((bool) $fh);
        });

        return $deferred->promise();
    }

    /**
     * {@inheritdoc}
     */
    public function readlink(string $path): Promise {
        $this->driver->reference($this->busy);
        $deferred = new Deferred;
        \uv_fs_readlink($this->loop, $path, function ($fh) use ($deferred) {
            $this->driver->unreference($this->busy);
            $deferred->resolve((bool) $fh);
        });

        return $deferred->promise();
    }

    /**
     * {@inheritdoc}
     */
    public function rename(string $from, string $to): Promise {
        $this->driver->reference($this->busy);
        $deferred = new Deferred;
        \uv_fs_rename($this->loop, $from, $to, function ($fh) use ($deferred, $from) {
            $this->driver->unreference($this->busy);
            StatCache::clear($from);
            $deferred->resolve((bool) $fh);
        });

        return $deferred->promise();
    }

    /**
     * {@inheritdoc}
     */
    public function unlink(string $path): Promise {
        $this->driver->reference($this->busy);
        $deferred = new Deferred;
        \uv_fs_unlink($this->loop, $path, function ($fh) use ($deferred, $path) {
            $this->driver->unreference($this->busy);
            StatCache::clear($path);
            $deferred->resolve((bool) $fh);
        });

        return $deferred->promise();
    }

    /**
     * {@inheritdoc}
     */
    public function mkdir(string $path, int $mode = 0644, bool $recursive = false): Promise {
        $this->driver->reference($this->busy);
        $deferred = new Deferred;

        if ($recursive) {
            $path = str_replace("/", DIRECTORY_SEPARATOR,  $path);
            $arrayPath = array_filter(explode(DIRECTORY_SEPARATOR, $path));
            $tmpPath = "";

            $callback = function () use (
                &$callback, &$arrayPath, &$tmpPath, $mode, $deferred
            ) {
                $tmpPath .= DIRECTORY_SEPARATOR . array_shift($arrayPath);

                if (empty($arrayPath)) {
                    \uv_fs_mkdir($this->loop, $tmpPath, $mode, function ($fh) use ($deferred) {
                        $this->driver->unreference($this->busy);
                        $deferred->resolve((bool) $fh);
                    });
                } else {
                    $this->isdir($tmpPath)->onResolve(function ($error, $result) use (
                        $callback, $tmpPath, $mode
                    ) {
                        if ($result) {
                            $callback();
                        } else {
                            \uv_fs_mkdir($this->loop, $tmpPath, $mode, $callback);
                        }
                    });
                }
            };

            $callback();
        } else {
            \uv_fs_mkdir($this->loop, $path, $mode, function ($fh) use ($deferred) {
                $this->driver->unreference($this->busy);
                $deferred->resolve((bool) $fh);
            });
        }

        return $deferred->promise();
    }

    /**
     * {@inheritdoc}
     */
    public function rmdir(string $path): Promise {
        $this->driver->reference($this->busy);
        $deferred = new Deferred;
        \uv_fs_rmdir($this->loop, $path, function ($fh) use ($deferred, $path) {
            $this->driver->unreference($this->busy);
            StatCache::clear($path);
            $deferred->resolve((bool) $fh);
        });

        return $deferred->promise();
    }

    /**
     * {@inheritdoc}
     */
    public function scandir(string $path): Promise {
        $this->driver->reference($this->busy);
        $deferred = new Deferred;
        uv_fs_readdir($this->loop, $path, 0, function ($fh, $data) use ($deferred, $path) {
            $this->driver->unreference($this->busy);
            if (empty($fh)) {
                $deferred->fail(new FilesystemException(
                    "Failed reading contents from {$path}"
                ));
            } else {
                $deferred->resolve($data);
            }
        });

        return $deferred->promise();
    }

    /**
     * {@inheritdoc}
     */
    public function chmod(string $path, int $mode): Promise {
        $this->driver->reference($this->busy);
        $deferred = new Deferred;
        \uv_fs_chmod($this->loop, $path, $mode, function ($fh) use ($deferred) {
            $this->driver->unreference($this->busy);
            $deferred->resolve((bool) $fh);
        });

        return $deferred->promise();
    }

    /**
     * {@inheritdoc}
     */
    public function chown(string $path, int $uid, int $gid): Promise {
        // @TODO Return a failure in windows environments
        $this->driver->reference($this->busy);
        $deferred = new Deferred;
        \uv_fs_chown($this->loop, $path, $uid, $gid, function ($fh) use ($deferred) {
            $this->driver->unreference($this->busy);
            $deferred->resolve((bool) $fh);
        });

        return $deferred->promise();
    }

    /**
     * {@inheritdoc}
     */
    public function touch(string $path): Promise {
        $this->driver->reference($this->busy);
        $atime = $mtime = time();
        $deferred = new Deferred;
        \uv_fs_utime($this->loop, $path, $mtime, $atime, function () use ($deferred) {
            // The uv_fs_utime() callback does not receive any args at this time
            $this->driver->unreference($this->busy);
            $deferred->resolve(true);
        });

        return $deferred->promise();
    }

    /**
     * {@inheritdoc}
     */
    public function get(string $path): Promise {
        return new Coroutine($this->doGet($path));
    }

    private function doGet($path): \Generator {
        $this->driver->reference($this->busy);
        $promise = $this->doFsOpen($path, $flags = \UV::O_RDONLY, $mode = 0);
        if (!$fh = yield $promise) {
            $this->driver->unreference($this->busy);
            throw new FilesystemException(
                "Failed opening file handle: {$path}"
            );
        }

        $deferred = new Deferred;
        $stat = (yield $this->doFsStat($fh));
        if (empty($stat)) {
            $this->driver->unreference($this->busy);
            $deferred->fail(new FilesystemException(
                "stat operation failed on open file handle"
            ));
        } elseif (!$stat["isfile"]) {
            \uv_fs_close($this->loop, $fh, function () use ($deferred) {
                $this->driver->unreference($this->busy);
                $deferred->fail(new FilesystemException(
                    "cannot buffer contents: path is not a file"
                ));
            });
        } else {
            $buffer = (yield $this->doFsRead($fh, $offset = 0, $stat["size"]));
            if ($buffer === false ) {
                \uv_fs_close($this->loop, $fh, function () use ($deferred) {
                    $this->driver->unreference($this->busy);
                    $deferred->fail(new FilesystemException(
                        "read operation failed on open file handle"
                    ));
                });
            } else {
                \uv_fs_close($this->loop, $fh, function () use ($deferred, $buffer) {
                    $this->driver->unreference($this->busy);
                    $deferred->resolve($buffer);
                });
            }
        }

        return yield $deferred->promise();
    }

    private function doFsOpen($path, $flags, $mode) {
        $deferred = new Deferred;
        \uv_fs_open($this->loop, $path, $flags, $mode, function ($fh) use ($deferred, $path) {
            $deferred->resolve($fh);
        });

        return $deferred->promise();
    }

    private function doFsStat($fh) {
        $deferred = new Deferred;
        \uv_fs_fstat($this->loop, $fh, function ($fh, $stat) use ($deferred) {
            if ($fh) {
                $stat["isdir"] = (bool) ($stat["mode"] & \UV::S_IFDIR);
                $stat["isfile"] = !$stat["isdir"];
                $deferred->resolve($stat);
            } else {
                $deferred->resolve();
            }
        });

        return $deferred->promise();
    }

    private function doFsRead($fh, $offset, $len) {
        $deferred = new Deferred;
        \uv_fs_read($this->loop, $fh, $offset, $len, function ($fh, $nread, $buffer) use ($deferred) {
            $deferred->resolve($nread < 0 ? false : $buffer);
        });

        return $deferred->promise();
    }

    /**
     * {@inheritdoc}
     */
    public function put(string $path, string $contents): Promise {
        return new Coroutine($this->doPut($path, $contents));
    }

    private function doPut($path, $contents): \Generator {
        $flags = \UV::O_WRONLY | \UV::O_CREAT;
        $mode = \UV::S_IRWXU | \UV::S_IRUSR;
        $this->driver->reference($this->busy);
        $promise = $this->doFsOpen($path, $flags, $mode);
        if (!$fh = yield $promise) {
            $this->driver->unreference($this->busy);
            throw new FilesystemException(
                "Failed opening write file handle"
            );
        }

        $deferred = new Deferred;
        $len = strlen($contents);
        \uv_fs_write($this->loop, $fh, $contents, $offset = 0, function ($fh, $result) use ($deferred, $len) {
            \uv_fs_close($this->loop, $fh, function() use ($deferred, $result, $len) {
                $this->driver->unreference($this->busy);
                if ($result < 0) {
                    $deferred->fail(new FilesystemException(
                        \uv_strerror($result)
                    ));
                } else {
                    $deferred->resolve($len);
                }
            });
        });

        return yield $deferred->promise();
    }
}