package rosa

import (
	"slices"
	"strconv"
	"strings"

	"hakurei.app/container/check"
	"hakurei.app/internal/pkg"
)

// llvmAttr holds the attributes that will be applied to a new [pkg.Artifact]
// containing a LLVM variant.
type llvmAttr struct {
	flags int

	// Concatenated with default environment for CMakeAttr.Env.
	env []string
	// Concatenated with generated entries for CMakeAttr.Cache.
	cmake [][2]string
	// Override CMakeAttr.Append.
	append []string
	// Concatenated with default dependencies for CMakeAttr.Extra.
	extra []pkg.Artifact
	// Concatenated with default fixup for CMakeAttr.Script.
	script string
	// Passed through to CMakeAttr.Prefix.
	prefix *check.Absolute
}

const (
	llvmProjectClang = 1 << iota
	llvmProjectLld

	llvmProjectAll = 1<<iota - 1

	llvmRuntimeCompilerRT = 1 << iota
	llvmRuntimeLibunwind
	llvmRuntimeLibc
	llvmRuntimeLibcxx
	llvmRuntimeLibcxxABI

	llvmAll        = 1<<iota - 1
	llvmRuntimeAll = llvmAll - (2 * llvmProjectAll) - 1
)

// llvmFlagName resolves a llvmAttr.flags project or runtime flag to its name.
func llvmFlagName(flag int) string {
	switch flag {
	case llvmProjectClang:
		return "clang"
	case llvmProjectLld:
		return "lld"

	case llvmRuntimeCompilerRT:
		return "compiler-rt"
	case llvmRuntimeLibunwind:
		return "libunwind"
	case llvmRuntimeLibc:
		return "libc"
	case llvmRuntimeLibcxx:
		return "libcxx"
	case llvmRuntimeLibcxxABI:
		return "libcxxabi"

	default:
		panic("invalid flag " + strconv.Itoa(flag))
	}
}

// newLLVM returns a [pkg.Artifact] containing a LLVM variant.
func (t Toolchain) newLLVM(variant string, attr *llvmAttr) pkg.Artifact {
	const (
		version  = "21.1.8"
		checksum = "8SUpqDkcgwOPsqHVtmf9kXfFeVmjVxl4LMn-qSE1AI_Xoeju-9HaoPNGtidyxyka"
	)
	if attr == nil {
		panic("LLVM attr must be non-nil")
	}

	var projects, runtimes []string
	for i := 1; i < llvmProjectAll; i <<= 1 {
		if attr.flags&i != 0 {
			projects = append(projects, llvmFlagName(i))
		}
	}
	for i := (llvmProjectAll + 1) << 1; i < llvmRuntimeAll; i <<= 1 {
		if attr.flags&i != 0 {
			runtimes = append(runtimes, llvmFlagName(i))
		}
	}

	var script, scriptEarly string

	cache := [][2]string{
		{"CMAKE_BUILD_TYPE", "Release"},

		{"LLVM_HOST_TRIPLE", `"${ROSA_TRIPLE}"`},
		{"LLVM_DEFAULT_TARGET_TRIPLE", `"${ROSA_TRIPLE}"`},
	}
	if len(projects) > 0 {
		cache = append(cache,
			[2]string{"LLVM_ENABLE_PROJECTS", `"${ROSA_LLVM_PROJECTS}"`})
	}
	if len(runtimes) > 0 {
		cache = append(cache,
			[2]string{"LLVM_ENABLE_RUNTIMES", `"${ROSA_LLVM_RUNTIMES}"`})
	}

	cmakeAppend := []string{"llvm"}
	if attr.append != nil {
		cmakeAppend = attr.append
	} else {
		cache = append(cache,
			[2]string{"LLVM_ENABLE_LIBCXX", "ON"},
			[2]string{"LLVM_USE_LINKER", "lld"},

			[2]string{"LLVM_INSTALL_BINUTILS_SYMLINKS", "ON"},
			[2]string{"LLVM_INSTALL_CCTOOLS_SYMLINKS", "ON"},
		)
	}

	extra := []pkg.Artifact{
		t.NewPython(),
		t.NewKernelHeaders(),
	}
	if t == toolchainStage3 {
		extra = nil
	}

	if attr.flags&llvmProjectClang != 0 {
		cache = append(cache,
			[2]string{"CLANG_DEFAULT_CXX_STDLIB", "libc++"},
			[2]string{"CLANG_DEFAULT_RTLIB", "compiler-rt"},
		)
	}
	if attr.flags&llvmProjectLld != 0 {
		script += `
ln -s ld.lld /work/system/bin/ld
`
	}
	if attr.flags&llvmRuntimeCompilerRT != 0 {
		if attr.append == nil {
			cache = append(cache,
				[2]string{"COMPILER_RT_USE_LLVM_UNWINDER", "ON"})
		}
	}
	if attr.flags&llvmRuntimeLibunwind != 0 {
		cache = append(cache,
			[2]string{"LIBUNWIND_USE_COMPILER_RT", "ON"})
	}
	if attr.flags&llvmRuntimeLibcxx != 0 {
		cache = append(cache,
			[2]string{"LIBCXX_HAS_MUSL_LIBC", "ON"},
			[2]string{"LIBCXX_USE_COMPILER_RT", "ON"},
		)

		if t > toolchainStage3 {
			// libcxxabi fails to compile if c++ headers not prefixed in /usr
			// is found by the compiler, and doing this is easier than
			// overriding CXXFLAGS; not using mv here to avoid chown failures
			scriptEarly += `
cp -r /system/include /usr/include && rm -rf /system/include
`
		}
	}
	if attr.flags&llvmRuntimeLibcxxABI != 0 {
		cache = append(cache,
			[2]string{"LIBCXXABI_USE_COMPILER_RT", "ON"},
			[2]string{"LIBCXXABI_USE_LLVM_UNWINDER", "ON"},
		)
	}

	return t.NewViaCMake("llvm", version, variant, pkg.NewHTTPGetTar(
		nil, "https://github.com/llvm/llvm-project/archive/refs/tags/"+
			"llvmorg-"+version+".tar.gz",
		mustDecode(checksum),
		pkg.TarGzip,
	), &CMakeAttr{
		Cache:  slices.Concat(cache, attr.cmake),
		Append: cmakeAppend,
		Extra:  slices.Concat(attr.extra, extra),
		Prefix: attr.prefix,

		Env: slices.Concat([]string{
			"ROSA_LLVM_PROJECTS=" + strings.Join(projects, ";"),
			"ROSA_LLVM_RUNTIMES=" + strings.Join(runtimes, ";"),
		}, attr.env),
		ScriptEarly: scriptEarly, Script: script + attr.script,
	})
}