/*!
Resources.
*/

use std::{fmt, iter, mem, slice};

use error::{Error, Result};
use image::*;
use util::{Pod, WideStr};

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

mod find;
pub use self::find::FindError;

mod art;

pub mod version_info;

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

/// Resources filesystem.
#[derive(Copy, Clone)]
pub struct Resources<'a> {
	section: &'a [u8],
	dir: &'a IMAGE_DATA_DIRECTORY,
}
impl<'a> Resources<'a> {
	/// Parse the bytes as PE resources.
	///
	/// No validation or integrity checking is done ahead of time.
	pub fn new(section: &'a [u8], dir: &'a IMAGE_DATA_DIRECTORY) -> Resources<'a> {
		// All offsets _except_ the data entry offsets are relative to the resource directory.
		// Data entry offsets are relative virtual addresses from the PE image.
		// Microsoft... Why would you do this?
		Resources { section, dir }
	}
	/// Gets the root directory.
	pub fn root(&self) -> Result<Directory<'a>> {
		Directory::try_from(*self, 0)
	}
	/// Filesystem consistency check.
	///
	/// Simply walks the filesystem checking all references are valid.
	pub fn fsck(&self) -> Result<()> {
		self.root()?.fsck()
	}

	#[inline]
	fn slice<T>(&self, offset: u32) -> Result<&'a T> where T: Pod {
		let start = offset as usize;
		let end = mem::size_of::<T>().wrapping_add(start);
		// Alignment checking
		if !cfg!(feature = "unsafe_alignment") && start & (mem::align_of::<T>() - 1) != 0 {
			return Err(Error::Misaligned);
		}
		// Range checking done by the indexing operator
		let bytes = self.section.get(start..end).ok_or(Error::Bounds)?;
		// Safe because size and alignment are checked and T is Pod
		Ok(unsafe { &*(bytes.as_ptr() as *const T) })
	}
	#[inline]
	#[allow(dead_code)] // unused for now...
	fn slice_len<T>(&self, offset: u32, len: usize) -> Result<&'a [T]> where T: Pod {
		let start = offset as usize;
		let size_of = mem::size_of::<T>().checked_mul(len).ok_or(Error::Overflow)?;
		let end = start.wrapping_add(size_of);
		// Alignment checking
		if !cfg!(feature = "unsafe_alignment") && start & (mem::align_of::<T>() - 1) != 0 {
			return Err(Error::Misaligned);
		}
		// Range checking done by the indexing operator
		let bytes = self.section.get(start..end).ok_or(Error::Bounds)?;
		Ok(unsafe { slice::from_raw_parts(bytes.as_ptr() as *const T, len) })
	}
	#[inline]
	fn slice_ws(&self, offset: u32) -> Result<&'a WideStr> {
		let offset = offset as usize;
		// Alignment checking
		if !cfg!(feature = "unsafe_alignment") && offset & 1 != 0 {
			return Err(Error::Misaligned);
		}
		// The name is prefixed by its length in words
		let len = self.section.get(offset..offset + 2).ok_or(Error::Bounds)?;
		let len = unsafe { *(len.as_ptr() as *const u16) } as usize;
		// Extract the name given its length
		let name = self.section.get(offset..offset + (len + 1) * 2).ok_or(Error::Bounds)?;
		let name = unsafe { slice::from_raw_parts(name.as_ptr() as *const u16, len + 1) };
		let name = unsafe { WideStr::from_words_unchecked(name) };
		Ok(name)
	}
}
impl<'a> fmt::Debug for Resources<'a> {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
		f.write_str("Resources { .. }")
	}
}

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

/// Directory.
#[derive(Copy, Clone)]
pub struct Directory<'a> {
	resources: Resources<'a>,
	image: &'a IMAGE_RESOURCE_DIRECTORY,
}
impl<'a> Directory<'a> {
	fn try_from(resources: Resources<'a>, offset: u32) -> Result<Directory<'a>> {
		let image: &IMAGE_RESOURCE_DIRECTORY = resources.slice(offset)?;
		// Validate the number of directory entries
		// This code has been carefully written to avoid panicking on overflow
		// It also validates the unsafe blocks below cf. size and alignment
		let entries_size = (image.NumberOfNamedEntries as usize + image.NumberOfIdEntries as usize) * mem::size_of::<IMAGE_RESOURCE_DIRECTORY_ENTRY>();
		let entries_offset = offset as usize + mem::size_of::<IMAGE_RESOURCE_DIRECTORY>();
		if entries_size > resources.section.len() - entries_offset {
			return Err(Error::Bounds);
		}
		Ok(Directory { resources, image })
	}
	/// Gets the resources.
	pub fn resources(&self) -> Resources<'a> {
		self.resources
	}
	/// Gets the underlying resource directory image.
	pub fn image(&self) -> &'a IMAGE_RESOURCE_DIRECTORY {
		self.image
	}
	/// Gets the directory entries.
	pub fn entries(&self) -> Entries<'a, impl Clone + FnMut(&'a IMAGE_RESOURCE_DIRECTORY_ENTRY) -> DirectoryEntry<'a>> {
		// Validated by constructor
		let slice = unsafe {
			let p = (self.image as *const IMAGE_RESOURCE_DIRECTORY).offset(1) as *const IMAGE_RESOURCE_DIRECTORY_ENTRY;
			let len = self.image.NumberOfNamedEntries as usize + self.image.NumberOfIdEntries as usize;
			slice::from_raw_parts(p, len)
		};
		let resources = self.resources;
		slice.iter().map(move |image| DirectoryEntry { resources, image })
	}
	/// Gets the named entries in this directory.
	///
	/// Note that while it would be a violation of the format spec, there's no strict safety guarantee that these are only named entries.
	pub fn named_entries(&self) -> Entries<'a, impl Clone + FnMut(&'a IMAGE_RESOURCE_DIRECTORY_ENTRY) -> DirectoryEntry<'a>> {
		// Validated by constructor
		let slice = unsafe {
			// Named entries come first in the array (see chapter "PE File Resources" in "Peering Inside the PE: A Tour of the Win32 Portable Executable File Format")
			let p = (self.image as *const IMAGE_RESOURCE_DIRECTORY).offset(1) as *const IMAGE_RESOURCE_DIRECTORY_ENTRY;
			let len = self.image.NumberOfNamedEntries as usize;
			slice::from_raw_parts(p, len)
		};
		let resources = self.resources;
		slice.iter().map(move |image| DirectoryEntry { resources, image })
	}
	/// Gets the id entries in this directory.
	///
	/// Note that while it would be a violation of the format spec, there's no strict safety guarantee that these are only id entries.
	pub fn id_entries(&self) -> Entries<'a, impl Clone + FnMut(&'a IMAGE_RESOURCE_DIRECTORY_ENTRY) -> DirectoryEntry<'a>> {
		// Validated by the constructor
		let slice = unsafe {
			// Id entries come last in the array
			let p = (self.image as *const IMAGE_RESOURCE_DIRECTORY).offset(1 + self.image.NumberOfNamedEntries as isize) as *const IMAGE_RESOURCE_DIRECTORY_ENTRY;
			let len = self.image.NumberOfIdEntries as usize;
			slice::from_raw_parts(p, len)
		};
		let resources = self.resources;
		slice.iter().map(move |image| DirectoryEntry { resources, image })
	}
	/// Filesystem consistency check.
	///
	/// Simply walks the filesystem checking all references are valid.
	pub fn fsck(&self) -> Result<()> {
		self.entries().try_for_each(|e| e.fsck())
	}
}
impl<'a> fmt::Debug for Directory<'a> {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
		f.debug_struct("Directory")
			.field("entries", &self.entries())
			.finish()
	}
}

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

/// Iterator over entries in a directory.
pub type Entries<'a, F> = iter::Map<slice::Iter<'a, IMAGE_RESOURCE_DIRECTORY_ENTRY>, F>;

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

/// Represents a resource name.
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
#[cfg_attr(feature = "serde", serde(untagged))]
#[cfg_attr(feature = "serde", derive(Serialize))]
pub enum Name<'a> {
	/// Resource ID.
	///
	/// Technically allows `u32` ids, but some Windows APIs will be unable to use resources with an id which isn't `u16`.
	Id(u32),
	/// UTF-16 named resource.
	Str(&'a WideStr),
}
impl<'a> From<u16> for Name<'a> {
	fn from(id: u16) -> Name<'a> {
		Name::Id(id as u32)
	}
}
impl<'a> From<&'a WideStr> for Name<'a> {
	fn from(ws: &'a WideStr) -> Name<'a> {
		Name::Str(ws)
	}
}

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

/// Data or directory entry.
#[derive(Copy, Clone, Debug)]
#[cfg_attr(feature = "serde", serde(untagged))]
#[cfg_attr(feature = "serde", derive(Serialize))]
pub enum Entry<'a> {
	Directory(Directory<'a>),
	DataEntry(DataEntry<'a>),
}
impl<'a> Entry<'a> {
	/// Returns some if the entry is a directory.
	pub fn dir(self) -> Option<Directory<'a>> {
		match self {
			Entry::Directory(dir) => Some(dir),
			Entry::DataEntry(_) => None,
		}
	}
	/// Returns some if the entry is a data entry.
	pub fn data(self) -> Option<DataEntry<'a>> {
		match self {
			Entry::Directory(_) => None,
			Entry::DataEntry(data) => Some(data),
		}
	}
}

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

/// Directory child entry.
///
/// Contains a name and a reference to the associated data or directory entry.
#[derive(Copy, Clone)]
pub struct DirectoryEntry<'a> {
	resources: Resources<'a>,
	image: &'a IMAGE_RESOURCE_DIRECTORY_ENTRY,
}
impl<'a> DirectoryEntry<'a> {
	/// Gets the resources.
	pub fn resources(&self) -> Resources<'a> {
		self.resources
	}
	/// Gets the underlying resource directory entry image.
	pub fn image(&self) -> &'a IMAGE_RESOURCE_DIRECTORY_ENTRY {
		self.image
	}
	/// Gets the name for this entry.
	pub fn name(&self) -> Result<Name<'a>> {
		if self.image.Name & 0x80000000 != 0 {
			let offset = self.image.Name & !0x80000000;
			let name = self.resources.slice_ws(offset)?;
			Ok(Name::Str(name))
		}
		else {
			// TODO: What if this doesn't fit in u16...
			Ok(Name::Id(self.image.Name))
		}
	}
	/// Returns if this entry is a directory.
	pub fn is_dir(&self) -> bool {
		self.image.Offset & 0x80000000 != 0
	}
	/// Returns the directory or data entry for this entry.
	pub fn entry(&self) -> Result<Entry<'a>> {
		if self.is_dir() {
			let offset = self.image.Offset & !0x80000000;
			Directory::try_from(self.resources, offset).map(Entry::Directory)
		}
		else {
			let offset = self.image.Offset;
			DataEntry::try_from(self.resources, offset).map(Entry::DataEntry)
		}
	}
	/// Filesystem consistency check.
	///
	/// Simply walks the filesystem checking all references are valid.
	pub fn fsck(&self) -> Result<()> {
		self.name()?;
		match self.entry()? {
			Entry::Directory(dir) => dir.fsck(),
			Entry::DataEntry(data) => data.fsck(),
		}
	}
}
impl<'a> fmt::Debug for DirectoryEntry<'a> {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
		f.debug_struct("DirectoryEntry")
			.field("name", &format_args!("{:?}", self.name()))
			.field("entry", &if self.is_dir() { "Directory(..)" } else { "DataEntry(..)" })
			.finish()
	}
}

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

/// Data entry.
#[derive(Copy, Clone)]
pub struct DataEntry<'a> {
	resources: Resources<'a>,
	image: &'a IMAGE_RESOURCE_DATA_ENTRY,
}
impl<'a> DataEntry<'a> {
	fn try_from(resources: Resources<'a>, offset: u32) -> Result<DataEntry<'a>> {
		let image = resources.slice(offset)?;
		Ok(DataEntry { resources, image })
	}
	/// Gets the resources.
	pub fn resources(&self) -> Resources<'a> {
		self.resources
	}
	/// Gets the underlying resource data entry image.
	pub fn image(&self) -> &'a IMAGE_RESOURCE_DATA_ENTRY {
		self.image
	}
	/// Gets the actual data.
	pub fn bytes(&self) -> Result<&'a [u8]> {
		let start = u32::checked_sub(self.image.OffsetToData, self.resources.dir.VirtualAddress).ok_or(Error::Overflow)?;
		let end = u32::checked_add(start, self.image.Size).ok_or(Error::Overflow)?;
		self.resources.section.get(start as usize..end as usize).ok_or(Error::Bounds)
	}
	/// Gets the data size.
	pub fn size(&self) -> usize {
		self.image.Size as usize
	}
	/// Gets the code page.
	pub fn code_page(&self) -> u32 {
		self.image.CodePage
	}
	/// Filesystem consistency check.
	///
	/// Simply walks the filesystem checking all references are valid.
	pub fn fsck(&self) -> Result<()> {
		self.bytes()?;
		Ok(())
	}
}
impl<'a> fmt::Debug for DataEntry<'a> {
	fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
		f.debug_struct("DataEntry")
			.field("data.len", &self.image.Size)
			.finish()
	}
}

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

/*
	"resources": {
		"version_info": { .. },
		"manifest": "<xml>",
		"root": [
			{
				"name": 12,
				"directory": [
					{
						"name": "IMPORTANT",
						"data": {
							size: 1234,
							code_page: 65001,
							bytes: "base64encoded=",
						}
					}
				]
			}
		]
	}
*/

#[cfg(feature = "serde")]
mod serde {
	use util::serde_helper::*;
	use super::{Resources, Directory, DirectoryEntry, DataEntry};

	impl<'a> Serialize for Resources<'a> {
		fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
			let mut state = serializer.serialize_struct("Resources", 3)?;
			state.serialize_field("version_info", &self.version_info().ok())?;
			state.serialize_field("manifest", &self.manifest().ok())?;
			state.serialize_field("root", &self.root().ok())?;
			state.end()
		}
	}
	impl<'a> Serialize for Directory<'a> {
		fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
			serializer.collect_seq(self.entries())
		}
	}
	impl<'a> Serialize for DirectoryEntry<'a> {
		fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
			let mut state = serializer.serialize_struct("DirectoryEntry", 2)?;
			state.serialize_field("name", &self.name().ok())?;
			state.serialize_field(if self.is_dir() { "directory" } else { "data" }, &self.entry().ok())?;
			state.end()
		}
	}
	impl<'a> Serialize for DataEntry<'a> {
		fn serialize<S: Serializer>(&self, serializer: S) -> Result<S::Ok, S::Error> {
			let is_human_readable = serializer.is_human_readable();
			let mut state = serializer.serialize_struct("DataEntry", 3)?;
			state.serialize_field("size", &self.size())?;
			state.serialize_field("code_page", &self.code_page())?;
			#[cfg(feature = "data-encoding")]
			(if is_human_readable {
				let string = self.bytes().map(|bytes| ::data_encoding::BASE64.encode(bytes));
				state.serialize_field("bytes", &string.as_ref().ok())
			}
			else {
				state.serialize_field("bytes", &self.bytes().ok())
			})?;
			#[cfg(not(feature = "data-encoding"))]
			state.serialize_field("bytes", &self.bytes().ok())?;
			state.end()
		}
	}
}

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

#[cfg(test)]
pub(crate) fn test(resources: Resources<'_>) -> Result<()> {
	fn test_dir(dir: Directory<'_>) {
		let _ = format!("{}", dir);
		let _ = format!("{:?}", dir);

		for entry in dir.entries() {
			let _ = format!("{:?}\n{:?}", entry.name(), entry);

			// Check consistency in id vs named entries
			if let Ok(name) = entry.name() {
				let mut id_entries;
				let mut named_entries;
				let mut entries: &mut Iterator<Item = _> = match name {
					Name::Id(_) => { id_entries = dir.id_entries(); &mut id_entries },
					Name::Str(_) => { named_entries = dir.named_entries(); &mut named_entries },
				};
				assert!((&mut entries).any(|entry| entry.name() == Ok(name)));
			}

			// Inspect the entry recursively
			match entry.entry() {
				Ok(Entry::DataEntry(data)) => {
					assert!(!entry.is_dir());
					let _ = format!("{:?}", data);
					let _size = data.size();
					let _code_page = data.code_page();
					let _bytes = data.bytes();
				},
				Ok(Entry::Directory(dir)) => {
					assert!(entry.is_dir());
					let _ = test_dir(dir);
				},
				Err(_) => (),
			}
		}
	}
	let _ = resources.fsck();
	println!("{}", resources);
	if let Ok(version_info) = resources.version_info() {
		self::version_info::test(version_info)
	}
	resources.root().map(test_dir)
}