use super::*;

use std::cmp::Ordering;
use std::ffi::OsString;


#[derive(Clone)]
pub struct BedrockFilePath {
    base: PathBuf,
    relative: PathBuf,
    bytes: Vec<u8>,
    entry_type: Option<EntryType>,
}

impl BedrockFilePath {
    pub fn from_buffer(buffer: [u8; 256], base: &Path) -> Option<Self> {
        let base = base.to_path_buf();
        let relative = buffer_to_path(buffer)?;
        let bytes = path_to_bytes(&relative)?;
        let entry_type = get_entry_type(base.join(&relative));
        assert_path_is_safe(&relative, &base)?;
        Some(Self { base, relative, bytes, entry_type })
    }

    /// Construct an instance from an absolute path and a prefix of that path.
    pub fn from_path(path: &Path, base: &Path) -> Option<Self> {
        let base = base.to_path_buf();
        let relative = path.strip_prefix(&base).ok()?.to_path_buf();
        let bytes = path_to_bytes(&relative)?;
        let entry_type = get_entry_type(base.join(&relative));
        assert_path_is_safe(&relative, &base)?;
        Some( Self { base, relative, bytes, entry_type } )
    }

    /// Get the base path used by this path.
    pub fn base(&self) -> &Path {
        &self.base
    }

    /// Get this path as a Bedrock-style path, which can be passed to
    /// a Bedrock program.
    pub fn as_bytes(&self) -> &[u8] {
        &self.bytes
    }

    /// Get this path as a byte buffer, from which a CircularPathBuffer
    /// can be populated.
    pub fn as_buffer(&self) -> [u8; 256] {
        let mut buffer: [u8; 256] = [0; 256];
        buffer[..self.bytes.len()].copy_from_slice(&self.bytes);
        return buffer;
    }

    /// Get this path as an absolute operating-system path, which can
    /// be used to open a file or directory.
    pub fn as_path(&self) -> PathBuf {
        self.base.join(&self.relative)
    }

    /// Get the entry type of this path.
    pub fn entry_type(&self) -> Option<EntryType> {
        self.entry_type
    }

    /// Get a path which represents the parent of this path.
    pub fn parent(&self) -> Option<Self> {
        #[cfg(target_family = "unix")] {
            Self::from_path(self.as_path().parent()?, &self.base)
        }
        #[cfg(target_family = "windows")] {
            if self.base.components().count() != 0 {
                // Sandboxed path, cannot ascend to a virtual root directory.
                Self::from_path(self.as_path().parent()?, &self.base)
            } else {
                // Unsandboxed path, we can ascend to a virtual root directory.
                match self.as_path().parent() {
                    // Ascend to concrete parent directory.
                    Some(parent) => Self::from_path(parent, &self.base),
                    // Ascend into a virtual root directory.
                    None => {
                        if self.relative.components().count() != 0 {
                            // Ascend from concrete path to virtual root.
                            let blank = PathBuf::from("");
                            BedrockFilePath::from_path(&blank, &blank)
                        } else {
                            // Cannot ascend above the virtual root.
                            None
                        }
                    },
                }
            }
        }
    }

    /// Returns true if the file would be hidden by the default file browser.
    pub fn is_hidden(&self) -> bool {
        #[cfg(target_family = "unix")] {
            if let Some(stem) = self.relative.file_stem() {
                if let Some(string) = stem.to_str() {
                    return string.starts_with('.');
                }
            }
        }
        #[cfg(target_family = "windows")] {
            use std::os::windows::fs::MetadataExt;
            // See https://learn.microsoft.com/en-us/windows/win32/fileio/file-attribute-constants
            // const FILE_ATTRIBUTE_HIDDEN: u32 = 0x00000002;
            // const FILE_ATTRIBUTE_NOT_CONTENT_INDEXED: u32 = 0x00002000;
            if let Ok(metadata) = std::fs::metadata(self.as_path()) {
                return metadata.file_attributes() & 0x2002 != 0;
            }
        }
        return false;
    }
}


/// Converts the contents of a CircularPathBuffer to a relative path.
fn buffer_to_path(bytes: [u8; 256]) -> Option<PathBuf> {
    // The buffer must be non-empty and slash-prefixed.
    if bytes[0] != ('/' as u8) {
        return None;
    }

    // Find the index of the first null byte.
    let mut null_i = None;
    for (i, b) in bytes.iter().enumerate() {
        if *b == 0x00 {
            null_i = Some(i);
            break;
        }
    }
    // Take a slice, excluding the leading slash, up to the trailing null.
    let slice = &bytes[1..null_i?];

    #[cfg(target_family = "unix")] {
        use std::os::unix::ffi::OsStringExt;
        let vec = Vec::from(slice);
        return Some(OsString::from_vec(vec).into())
    }
    #[cfg(target_family = "windows")] {
        use std::os::windows::ffi::OsStringExt;
        let mut string = String::from_utf8_lossy(slice).to_string();
        // Convert drive-current-directory paths to drive-root paths. This is
        // needed because the paths C: and C:/ point to separate directories,
        // but trailing forward-slashes are optional in Bedrock.
        if string.ends_with(':') {
            string.push('/');
        }
        let utf16: Vec<u16> = string.replace(r"/", r"\").encode_utf16().collect();
        return Some(OsString::from_wide(&utf16).into())
    }
}

/// Convert an operating system path to a Bedrock-style byte path.
///
/// A byte path contains at most 255 bytes, and is not null-terminated.
fn path_to_bytes(path: &Path) -> Option<Vec<u8>> {
    #[cfg(target_family = "unix")]
    let string = path.as_os_str().to_str()?.to_string();
    #[cfg(target_family = "windows")]
    let string = path.as_os_str().to_str()?.replace(r"\", r"/");

    // Remove any trailing forward-slash and add a leading forward-slash.
    let mut prefixed_string = String::from("/");
    prefixed_string.push_str(string.trim_end_matches('/'));
    let slice = prefixed_string.as_bytes();

    // Error if bytes does not fit into a CircularPathBuffer.
    if slice.len() > 255 { return None; }

    Some(Vec::from(slice))
}

/// Returns true if a relative path can be safely attached to a base without
/// breaking out of the sandbox.
fn assert_path_is_safe(relative: &Path, _base: &Path) -> Option<()> {
    #[cfg(target_family = "unix")] {
        // Error if path contains special components.
        for component in relative.components() {
            match component {
                Component::Normal(_) => continue,
                _ => return None,
            }
        }
    }
    #[cfg(target_family = "windows")] {
        // If the base path is empty, the relative path needs to be able to
        // contain the prefix and root element. If the base path is not
        // empty, the relative path must not contain these elements else
        // they will override the base path when joined.
        if _base.components().count() != 0 {
            for component in relative.components() {
                match component {
                    Component::Normal(_) => continue,
                    _ => return None,
                }
            }
        }
    }
    return Some(());
}

fn get_entry_type(absolute: PathBuf) -> Option<EntryType> {
    #[cfg(target_family = "windows")] {
        // If path is empty, this is a virtual root directory.
        if absolute.components().count() == 0 {
            return Some(EntryType::Directory)
        }
    }
    let metadata = std::fs::metadata(absolute).ok()?;
    if metadata.is_file() {
        Some(EntryType::File)
    } else if metadata.is_dir() {
        Some(EntryType::Directory)
    } else {
        None
    }
}

impl std::fmt::Debug for BedrockFilePath {
    fn fmt(&self, f: &mut std::fmt::Formatter) -> Result<(), std::fmt::Error> {
        self.as_path().fmt(f)
    }
}

// ---------------------------------------------------------------------------

impl PartialEq for BedrockFilePath {
    fn eq(&self, other: &Self) -> bool {
        self.bytes == other.bytes && self.entry_type == other.entry_type
    }
}

impl Eq for BedrockFilePath {}

impl PartialOrd for BedrockFilePath {
    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
        Some(self.cmp(other))
    }
}

impl Ord for BedrockFilePath {
    fn cmp(&self, other: &Self) -> Ordering {
        match self.entry_type.cmp(&other.entry_type) {
            Ordering::Equal => compare_ascii_slices(&self.bytes, &other.bytes),
            ordering => ordering,
        }
    }
}

// Compare two ASCII byte-slices in case-agnostic alphabetic order.
fn compare_ascii_slices(left: &[u8], right: &[u8]) -> Ordering {
    let l = std::cmp::min(left.len(), right.len());
    let lhs = &left[..l];
    let rhs = &right[..l];

    for i in 0..l {
        let a = remap_ascii(lhs[i]);
        let b = remap_ascii(rhs[i]);
        match a.cmp(&b) {
            Ordering::Equal => (),
            non_eq => return non_eq,
        }
    }

    left.len().cmp(&right.len())
}

// Remap ASCII values so that they sort in case-agnostic alphabetic order:
//    !"#$%&'()*+,-./0123456789:;<=>?
//   @`AaBbCcDdEeFfGgHhIiJjKkLlMmNnOo
//   PpQqRrSsTtUuVvWwXxYyZz[{\|]}^~_
fn remap_ascii(c: u8) -> u8 {
    if 0x40 <= c && c <= 0x5F {
        (c - 0x40) * 2 + 0x40
    } else if 0x60 <= c && c <= 0x7F {
        (c - 0x60) * 2 + 0x41
    } else {
        c
    }
}