package sandbox

import (
	"fmt"
	"runtime"
)

// ArchProfile describes a cross-compilation target. When the user passes
// `sorcery cast <spell> --target aarch64`, the matching ArchProfile is
// attached to the sandbox so the compiler can produce ARM64 binaries even
// when the host is x86_64.
type ArchProfile struct {
	Name     string   // e.g., "aarch64", "x86_64"
	Triple   string   // e.g., "aarch64-linux-gnu"
	Compiler string   // e.g., "/usr/bin/aarch64-linux-gnu-gcc"
	Flags    []string // -march, -mtune, etc.
}

// HostArch returns the profile for the current host.
func HostArch() ArchProfile {
	switch runtime.GOARCH {
	case "arm64":
		return ArchProfile{Name: "aarch64", Triple: "aarch64-linux-gnu", Compiler: "gcc"}
	default:
		return ArchProfile{Name: "x86_64", Triple: "x86_64-linux-gnu", Compiler: "gcc"}
	}
}

// SetTarget configures the sandbox for a specific target. If `arch` differs
// from the host arch, CROSS_COMPILE / CC are set so the spell's BUILD script
// transparently invokes the cross-toolchain.
func (b *Box) SetTarget(arch string) error {
	if arch == "" {
		return nil
	}
	if arch == HostArch().Name {
		return nil
	}
	profile, ok := knownProfiles[arch]
	if !ok {
		return fmt.Errorf("sandbox: no toolchain profile for arch %q", arch)
	}
	b.Env["ARCH"] = arch
	b.Env["CROSS_COMPILE"] = profile.Triple + "-"
	b.Env["CC"] = profile.Compiler
	b.Env["HOST"] = profile.Triple
	return nil
}

var knownProfiles = map[string]ArchProfile{
	"aarch64": {
		Name:     "aarch64",
		Triple:   "aarch64-linux-gnu",
		Compiler: "aarch64-linux-gnu-gcc",
		Flags:    []string{"-march=armv8-a", "-O2"},
	},
	"x86_64": {
		Name:     "x86_64",
		Triple:   "x86_64-linux-gnu",
		Compiler: "gcc",
		Flags:    []string{"-march=x86-64", "-O2"},
	},
}