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use rspirv::spirv::MemoryModel;
use rustc_target::spec::{Cc, LinkerFlavor, PanicStrategy, Target, TargetOptions};
use spirv_tools::TargetEnv;

const ARCH: &str = "spirv";

pub struct SpirvTarget {
    env: TargetEnv,
    vendor: String,
}

impl SpirvTarget {
    pub fn memory_model(&self) -> MemoryModel {
        match self.env {
            TargetEnv::Universal_1_0
            | TargetEnv::Universal_1_1
            | TargetEnv::Universal_1_2
            | TargetEnv::Universal_1_3
            | TargetEnv::Universal_1_4
            | TargetEnv::Universal_1_5 => MemoryModel::Simple,

            TargetEnv::OpenGL_4_0
            | TargetEnv::OpenGL_4_1
            | TargetEnv::OpenGL_4_2
            | TargetEnv::OpenGL_4_3
            | TargetEnv::OpenGL_4_5 => MemoryModel::GLSL450,

            TargetEnv::OpenCL_2_1
            | TargetEnv::OpenCL_2_2
            | TargetEnv::OpenCL_1_2
            | TargetEnv::OpenCLEmbedded_1_2
            | TargetEnv::OpenCL_2_0
            | TargetEnv::OpenCLEmbedded_2_0
            | TargetEnv::OpenCLEmbedded_2_1
            | TargetEnv::OpenCLEmbedded_2_2 => MemoryModel::OpenCL,

            TargetEnv::Vulkan_1_0
            | TargetEnv::Vulkan_1_1
            | TargetEnv::WebGPU_0
            | TargetEnv::Vulkan_1_1_Spirv_1_4
            | TargetEnv::Vulkan_1_2 => MemoryModel::Vulkan,
        }
    }

    pub fn spirv_version(&self) -> (u8, u8) {
        #[allow(clippy::match_same_arms)]
        match self.env {
            TargetEnv::Universal_1_0 => (1, 0),
            TargetEnv::Universal_1_1 => (1, 1),
            TargetEnv::Universal_1_2 => (1, 2),
            TargetEnv::Universal_1_3 => (1, 3),
            TargetEnv::Universal_1_4 => (1, 4),
            TargetEnv::Universal_1_5 => (1, 5),

            TargetEnv::OpenGL_4_0 => (1, 0),
            TargetEnv::OpenGL_4_1 => (1, 0),
            TargetEnv::OpenGL_4_2 => (1, 0),
            TargetEnv::OpenGL_4_3 => (1, 0),
            TargetEnv::OpenGL_4_5 => (1, 0),

            TargetEnv::OpenCL_1_2 => (1, 0),
            TargetEnv::OpenCL_2_0 => (1, 0),
            TargetEnv::OpenCL_2_1 => (1, 0),
            TargetEnv::OpenCL_2_2 => (1, 2),
            TargetEnv::OpenCLEmbedded_1_2 => (1, 0),
            TargetEnv::OpenCLEmbedded_2_0 => (1, 0),
            TargetEnv::OpenCLEmbedded_2_1 => (1, 0),
            TargetEnv::OpenCLEmbedded_2_2 => (1, 2),

            TargetEnv::Vulkan_1_0 => (1, 0),
            TargetEnv::Vulkan_1_1 => (1, 3),
            TargetEnv::WebGPU_0 => (1, 3),
            TargetEnv::Vulkan_1_1_Spirv_1_4 => (1, 4),
            TargetEnv::Vulkan_1_2 => (1, 5),
        }
    }

    fn init_target_opts(&self) -> TargetOptions {
        let mut o = TargetOptions::default();
        o.simd_types_indirect = false;
        o.allows_weak_linkage = false;
        o.crt_static_allows_dylibs = true;
        o.dll_prefix = "".into();
        o.dll_suffix = ".spv.json".into();
        o.dynamic_linking = true;
        o.emit_debug_gdb_scripts = false;
        o.linker_flavor = LinkerFlavor::Unix(Cc::No);
        o.panic_strategy = PanicStrategy::Abort;
        o.os = "unknown".into();
        o.env = self.env.to_string().into();
        o.vendor = self.vendor.clone().into();
        // TODO: Investigate if main_needs_argc_argv is useful (for building exes)
        o.main_needs_argc_argv = false;
        o
    }

    pub fn rustc_target(&self) -> Target {
        Target {
            llvm_target: self.to_string().into(),
            pointer_width: 32,
            data_layout: "e-m:e-p:32:32:32-i64:64-n8:16:32:64".into(),
            arch: ARCH.into(),
            options: self.init_target_opts(),
        }
    }
}

impl std::str::FromStr for SpirvTarget {
    type Err = InvalidTarget;

    fn from_str(target: &str) -> Result<Self, Self::Err> {
        let mut iter = target.split('-');
        let error = || InvalidTarget(target.into());

        if iter.next().map_or(true, |arch| arch != ARCH) {
            return Err(error());
        }

        let vendor = iter.next().map(From::from).ok_or_else(error)?;

        let env = iter
            .next()
            .and_then(|env| env.parse().ok())
            .ok_or_else(error)?;

        if iter.next().is_some() {
            return Err(error());
        }

        let result = Self { env, vendor };

        if result.memory_model() == MemoryModel::OpenCL {
            return Err(error());
        }

        Ok(result)
    }
}

impl std::fmt::Display for SpirvTarget {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "{}-{}-{}", ARCH, self.vendor, self.env)
    }
}

#[derive(Debug)]
pub struct InvalidTarget(String);

impl std::error::Error for InvalidTarget {}
impl std::fmt::Display for InvalidTarget {
    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
        write!(f, "Invalid target `{}`.", self.0)
    }
}