// Copyright 2023 The LightningBolt Authors
// SPDX-License-Identifier: MIT

#include <base/Types.hpp>
#include <cstring>
#include <span>

namespace lightningbolt {

	/// Elf structures, only applicable to Simpsons Skateboarding
	namespace elf {

		/// Table entry in the ELF. We use this to create file names.
		struct [[gnu::packed]] BoltTableEntry {
			/// Pointer to filename. Should be adjusted
			u32 filenamePtr;
			u16 entryId; // (GID >> 8) | ID
			u16 groupId; // (entryId & 0xff00)
		};

		/// Offsets in the ELF to the table.
		struct BoltTableOffsets {
			u32 usTable;
		};

		/// Convert a address to ELF file offset.
		constexpr u32 AddressToElfFileOffset(u32 address) {
			constexpr u32 LoadAddress = 0x00100000;
			constexpr u32 SectionOffset = 0x80;
			return (address - LoadAddress) + SectionOffset;
		}

		static constexpr BoltTableOffsets BoltTableOffsets = { .usTable = AddressToElfFileOffset(0x0033d400) };

	} // namespace elf

	struct [[gnu::packed]] BoltGroupEntry {
		u32 unk;
		u32 fileSize;
		u32 fileOffset;
		u32 unk3; // name hash?
	};

	struct [[gnu::packed]] BoltGroupDescriptor {
		u8 unk;
		u8 unk2;
		u8 unk3;
		u8 entryCount;

		u32 groupSize;
		u32 groupOffset;

		// PS2 pointer padding; bolt library stuffs something here
		u32 pad;

		u32 EntryCount() {
			// Special case: 0x0 == 256 entries.
			// I have NO idea why they did it like this,
			// this really seems extra when they could have
			// used a short field in the same exact space.
			if(entryCount == 0x0)
				return 256;
			return entryCount;
		}

		std::span<BoltGroupEntry> Entries(u8* base) { return { std::bit_cast<BoltGroupEntry*>(&base[groupOffset]), EntryCount() }; }
	};

	struct [[gnu::packed]] BoltLibraryHeader {
		static constexpr char VALID_MAGIC[] = "BOLT";
		char magic[4];

		u8 unkmaybemagic[2]; // could be platform flags ?

		u8 unk;
		u8 unk2;

		u8 unk3;
		u8 unk4;
		u8 unk5;
		u8 groupCount;

		u32 libSize;

		std::span<BoltGroupDescriptor> GroupDescriptors() {
			// The group descriptors are after the primary library header
			return { std::bit_cast<BoltGroupDescriptor*>(this + 1), groupCount };
		}

		inline bool Validate() const { return !std::memcmp(&magic[0], &VALID_MAGIC[0], sizeof(magic)); }
	};

} // namespace lightningbolt