#![deny(future_incompatible, let_underscore, nonstandard_style, clippy::all)]
#![warn(clippy::pedantic)]
#![allow(clippy::too_many_lines, clippy::wildcard_imports)]

use std::{
    collections::{HashMap, HashSet},
    fs,
    num::NonZeroUsize,
    path::Path,
    sync::Arc,
};

use clap::Parser;
use parking_lot::{Mutex, RwLock};

use nac3core::{
    codegen::{
        concrete_type::ConcreteTypeStore, irrt::load_irrt, CodeGenLLVMOptions,
        CodeGenTargetMachineOptions, CodeGenTask, DefaultCodeGenerator, WithCall, WorkerRegistry,
    },
    inkwell::{
        memory_buffer::MemoryBuffer, module::Linkage, passes::PassBuilderOptions,
        support::is_multithreaded, targets::*, OptimizationLevel,
    },
    nac3parser::{
        ast::{Constant, Expr, ExprKind, StmtKind, StrRef},
        parser,
    },
    symbol_resolver::SymbolResolver,
    toplevel::{
        composer::{ComposerConfig, TopLevelComposer},
        helper::parse_parameter_default_value,
        type_annotation::*,
        TopLevelDef,
    },
    typecheck::{
        type_inferencer::PrimitiveStore,
        typedef::{FunSignature, Type, Unifier, VarMap},
    },
};

use basic_symbol_resolver::*;

mod basic_symbol_resolver;

/// Command-line argument parser definition.
#[derive(Parser)]
#[command(author, version, about, long_about = None)]
struct CommandLineArgs {
    /// The name of the input file.
    file_name: String,

    /// The number of threads allocated to processing the source file. If 0 is passed to this
    /// parameter, all available threads will be used for compilation.
    #[arg(short = 'T', default_value_t = 1)]
    threads: u32,

    /// The level to optimize the LLVM IR.
    #[arg(short = 'O', default_value_t = 2, value_parser = clap::value_parser!(u32).range(0..=3))]
    opt_level: u32,

    /// Whether to emit LLVM IR at the end of every module.
    ///
    /// If multithreaded compilation is also enabled, each thread will emit its own module.
    #[arg(long, default_value_t = false)]
    emit_llvm: bool,

    /// The target triple to compile for.
    #[arg(long)]
    triple: Option<String>,

    /// The target CPU to compile for.
    #[arg(long)]
    mcpu: Option<String>,

    /// Additional target features to enable/disable, specified using the `+`/`-` prefixes.
    #[arg(long)]
    target_features: Option<String>,
}

fn handle_typevar_definition(
    var: &Expr,
    resolver: &(dyn SymbolResolver + Send + Sync),
    def_list: &[Arc<RwLock<TopLevelDef>>],
    unifier: &mut Unifier,
    primitives: &PrimitiveStore,
) -> Result<Type, HashSet<String>> {
    let ExprKind::Call { func, args, .. } = &var.node else {
        return Err(HashSet::from([format!(
            "expression {var:?} cannot be handled as a generic parameter in global scope"
        )]));
    };

    match &func.node {
        ExprKind::Name { id, .. } if id == &"TypeVar".into() => {
            let ExprKind::Constant { value: Constant::Str(ty_name), .. } = &args[0].node else {
                return Err(HashSet::from([format!(
                    "Expected string constant for first parameter of `TypeVar`, got {:?}",
                    &args[0].node
                )]));
            };
            let generic_name: StrRef = ty_name.to_string().into();

            let constraints = args
                .iter()
                .skip(1)
                .map(|x| -> Result<Type, HashSet<String>> {
                    let ty = parse_ast_to_type_annotation_kinds(
                        resolver,
                        def_list,
                        unifier,
                        primitives,
                        x,
                        HashMap::new(),
                    )?;
                    get_type_from_type_annotation_kinds(
                        def_list, unifier, primitives, &ty, &mut None,
                    )
                })
                .collect::<Result<Vec<_>, _>>()?;
            let loc = func.location;

            if constraints.len() == 1 {
                return Err(HashSet::from([format!(
                    "A single constraint is not allowed (at {loc})"
                )]));
            }

            Ok(unifier.get_fresh_var_with_range(&constraints, Some(generic_name), Some(loc)).ty)
        }

        ExprKind::Name { id, .. } if id == &"ConstGeneric".into() => {
            if args.len() != 2 {
                return Err(HashSet::from([format!(
                    "Expected 2 arguments for `ConstGeneric`, got {}",
                    args.len()
                )]));
            }

            let ExprKind::Constant { value: Constant::Str(ty_name), .. } = &args[0].node else {
                return Err(HashSet::from([format!(
                    "Expected string constant for first parameter of `ConstGeneric`, got {:?}",
                    &args[0].node
                )]));
            };
            let generic_name: StrRef = ty_name.to_string().into();

            let ty = parse_ast_to_type_annotation_kinds(
                resolver,
                def_list,
                unifier,
                primitives,
                &args[1],
                HashMap::new(),
            )?;
            let constraint =
                get_type_from_type_annotation_kinds(def_list, unifier, primitives, &ty, &mut None)?;
            let loc = func.location;

            Ok(unifier.get_fresh_const_generic_var(constraint, Some(generic_name), Some(loc)).ty)
        }

        _ => Err(HashSet::from([format!(
            "expression {var:?} cannot be handled as a generic parameter in global scope"
        )])),
    }
}

fn handle_assignment_pattern(
    targets: &[Expr],
    value: &Expr,
    resolver: Arc<dyn SymbolResolver + Send + Sync>,
    internal_resolver: &ResolverInternal,
    composer: &mut TopLevelComposer,
) -> Result<(), String> {
    if targets.len() == 1 {
        let target = &targets[0];

        match &target.node {
            ExprKind::Name { id, .. } => {
                let def_list = composer.extract_def_list();
                let unifier = &mut composer.unifier;
                let primitives = &composer.primitives_ty;

                if let Ok(var) =
                    handle_typevar_definition(value, &*resolver, &def_list, unifier, primitives)
                {
                    internal_resolver.add_id_type(*id, var);
                    Ok(())
                } else if let Ok(val) = parse_parameter_default_value(value, &*resolver) {
                    internal_resolver.add_module_global(*id, val);
                    let (name, def_id, _) = composer
                        .register_top_level_var(
                            *id,
                            None,
                            Some(resolver.clone()),
                            "__main__",
                            target.location,
                        )
                        .unwrap();
                    internal_resolver.add_id_def(name, def_id);
                    Ok(())
                } else {
                    Err(format!("fails to evaluate this expression `{:?}` as a constant or generic parameter at {}",
                        target.node,
                        target.location,
                    ))
                }
            }
            ExprKind::List { elts, .. } | ExprKind::Tuple { elts, .. } => {
                handle_assignment_pattern(elts, value, resolver, internal_resolver, composer)?;
                Ok(())
            }
            _ => Err(format!("assignment to {target:?} is not supported at {}", target.location)),
        }
    } else {
        match &value.node {
            ExprKind::List { elts, .. } | ExprKind::Tuple { elts, .. } => {
                if elts.len() == targets.len() {
                    for (tar, val) in targets.iter().zip(elts) {
                        handle_assignment_pattern(
                            std::slice::from_ref(tar),
                            val,
                            resolver.clone(),
                            internal_resolver,
                            composer,
                        )?;
                    }
                    Ok(())
                } else {
                    Err(format!(
                        "number of elements to unpack does not match (expect {}, found {}) at {}",
                        targets.len(),
                        elts.len(),
                        value.location
                    ))
                }
            }
            _ => Err(format!("unpack of this expression is not supported at {}", value.location)),
        }
    }
}

fn handle_global_var(
    target: &Expr,
    value: Option<&Expr>,
    resolver: &Arc<dyn SymbolResolver + Send + Sync>,
    internal_resolver: &ResolverInternal,
    composer: &mut TopLevelComposer,
) -> Result<(), String> {
    let ExprKind::Name { id, .. } = target.node else {
        return Err(format!(
            "global variable declaration must be an identifier (at {})",
            target.location,
        ));
    };

    let Some(value) = value else {
        return Err(format!("global variable `{id}` must be initialized in its definition"));
    };

    if let Ok(val) = parse_parameter_default_value(value, &**resolver) {
        internal_resolver.add_module_global(id, val);
        let (name, def_id, _) = composer
            .register_top_level_var(id, None, Some(resolver.clone()), "__main__", target.location)
            .unwrap();
        internal_resolver.add_id_def(name, def_id);
        Ok(())
    } else {
        Err(format!(
            "failed to evaluate this expression `{:?}` as a constant at {}",
            target.node, target.location,
        ))
    }
}

fn main() {
    let cli = CommandLineArgs::parse();
    let CommandLineArgs { file_name, threads, opt_level, emit_llvm, triple, mcpu, target_features } =
        cli;

    Target::initialize_all(&InitializationConfig::default());

    let host_target_machine = CodeGenTargetMachineOptions::from_host();
    let triple = triple.unwrap_or(host_target_machine.triple.clone());
    let mcpu = mcpu
        .map(|arg| if arg == "native" { host_target_machine.cpu.clone() } else { arg })
        .unwrap_or_default();
    let target_features = target_features.unwrap_or_default();
    let threads = if is_multithreaded() {
        if threads == 0 {
            std::thread::available_parallelism().map(NonZeroUsize::get).unwrap_or(1usize)
        } else {
            threads as usize
        }
    } else {
        if threads != 1 {
            println!("Warning: Number of threads specified in command-line but multithreading is disabled in LLVM at build time! Defaulting to single-threaded compilation");
        }
        1
    };
    let opt_level = match opt_level {
        0 => OptimizationLevel::None,
        1 => OptimizationLevel::Less,
        2 => OptimizationLevel::Default,
        // The default behavior for -O<n> where n>3 defaults to O3 for both Clang and GCC
        _ => OptimizationLevel::Aggressive,
    };

    let target_machine_options = CodeGenTargetMachineOptions {
        triple,
        cpu: mcpu,
        features: target_features,
        reloc_mode: RelocMode::PIC,
        ..host_target_machine
    };
    let target_machine = target_machine_options
        .create_target_machine(opt_level)
        .expect("couldn't create target machine");

    let context = nac3core::inkwell::context::Context::create();

    let size_t =
        context.ptr_sized_int_type(&target_machine.get_target_data(), None).get_bit_width();

    let program = match fs::read_to_string(file_name.clone()) {
        Ok(program) => program,
        Err(err) => {
            panic!("Cannot open input file: {err}");
        }
    };

    let primitive: PrimitiveStore = TopLevelComposer::make_primitives(size_t).0;
    let (mut composer, builtins_def, builtins_ty) =
        TopLevelComposer::new(vec![], vec![], ComposerConfig::default(), size_t);

    let internal_resolver: Arc<ResolverInternal> = ResolverInternal {
        id_to_type: builtins_ty.into(),
        id_to_def: builtins_def.into(),
        module_globals: Mutex::default(),
        str_store: Mutex::default(),
    }
    .into();
    let resolver =
        Arc::new(Resolver(internal_resolver.clone())) as Arc<dyn SymbolResolver + Send + Sync>;

    // Process IRRT
    let irrt = load_irrt(&context, resolver.as_ref());
    if emit_llvm {
        irrt.write_bitcode_to_path(Path::new("irrt.bc"));
    }

    // Process the Python script
    let parser_result = parser::parse_program(&program, file_name.into()).unwrap();

    for stmt in parser_result {
        match &stmt.node {
            StmtKind::Assign { targets, value, .. } => {
                if let Err(err) = handle_assignment_pattern(
                    targets,
                    value,
                    resolver.clone(),
                    internal_resolver.as_ref(),
                    &mut composer,
                ) {
                    panic!("{err}");
                }
            }

            StmtKind::AnnAssign { target, value, .. } => {
                if let Err(err) = handle_global_var(
                    target,
                    value.as_ref().map(Box::as_ref),
                    &resolver,
                    internal_resolver.as_ref(),
                    &mut composer,
                ) {
                    panic!("{err}");
                }
            }

            // allow (and ignore) "from __future__ import annotations"
            StmtKind::ImportFrom { module, names, .. }
                if module == &Some("__future__".into())
                    && names.len() == 1
                    && names[0].name == "annotations".into() => {}
            _ => {
                let (name, def_id, ty) = composer
                    .register_top_level(stmt, Some(resolver.clone()), "__main__", true)
                    .unwrap();
                internal_resolver.add_id_def(name, def_id);
                if let Some(ty) = ty {
                    internal_resolver.add_id_type(name, ty);
                }
            }
        }
    }

    let signature = FunSignature { args: vec![], ret: primitive.int32, vars: VarMap::new() };
    let mut store = ConcreteTypeStore::new();
    let mut cache = HashMap::new();
    let signature = store.from_signature(&mut composer.unifier, &primitive, &signature, &mut cache);
    let signature = store.add_cty(signature);

    if let Err(errors) = composer.start_analysis(true) {
        let error_count = errors.len();
        eprintln!("{error_count} error(s) occurred during top level analysis.");

        for (error_i, error) in errors.iter().enumerate() {
            let error_num = error_i + 1;
            eprintln!("=========== ERROR {error_num}/{error_count} ============");
            eprintln!("{error}");
        }
        eprintln!("==================================");

        panic!("top level analysis failed");
    }

    let top_level = Arc::new(composer.make_top_level_context());

    let instance = {
        let defs = top_level.definitions.read();
        let mut instance = defs[resolver
            .get_identifier_def("run".into())
            .unwrap_or_else(|_| panic!("cannot find run() entry point"))
            .0]
            .write();
        let TopLevelDef::Function { instance_to_stmt, instance_to_symbol, .. } = &mut *instance
        else {
            unreachable!()
        };
        instance_to_symbol.insert(String::new(), "run".to_string());
        instance_to_stmt[""].clone()
    };

    let llvm_options = CodeGenLLVMOptions { opt_level, target: target_machine_options };

    let task = CodeGenTask {
        subst: Vec::default(),
        symbol_name: "run".to_string(),
        body: instance.body,
        signature,
        resolver,
        store,
        unifier_index: instance.unifier_id,
        calls: instance.calls,
        id: 0,
    };

    let membuffers: Arc<Mutex<Vec<Vec<u8>>>> = Arc::default();
    let membuffer = membuffers.clone();

    let f = Arc::new(WithCall::new(Box::new(move |module| {
        let buffer = module.write_bitcode_to_memory();
        let buffer = buffer.as_slice().into();
        membuffer.lock().push(buffer);
    })));
    let threads = (0..threads)
        .map(|i| Box::new(DefaultCodeGenerator::new(format!("module{i}"), size_t)))
        .collect();
    let (registry, handles) = WorkerRegistry::create_workers(threads, top_level, &llvm_options, &f);
    registry.add_task(task);
    registry.wait_tasks_complete(handles);

    // Link all modules together into `main`
    let buffers = membuffers.lock();
    let main = context
        .create_module_from_ir(MemoryBuffer::create_from_memory_range(&buffers[0], "main"))
        .unwrap();
    if emit_llvm {
        main.write_bitcode_to_path(Path::new("main.bc"));
    }

    for (idx, buffer) in buffers.iter().skip(1).enumerate() {
        let other = context
            .create_module_from_ir(MemoryBuffer::create_from_memory_range(buffer, "main"))
            .unwrap();

        if emit_llvm {
            other.write_bitcode_to_path(Path::new(&format!("module{idx}.bc")));
        }

        main.link_in_module(other).unwrap();
    }

    main.link_in_module(irrt).unwrap();

    // Private all functions except "run"
    let mut function_iter = main.get_first_function();
    while let Some(func) = function_iter {
        if func.count_basic_blocks() > 0 && func.get_name().to_str().unwrap() != "run" {
            func.set_linkage(Linkage::Private);
        }
        function_iter = func.get_next_function();
    }

    // Optimize `main`
    let pass_options = PassBuilderOptions::create();
    pass_options.set_merge_functions(true);
    let passes = format!("default<O{}>", opt_level as u32);
    let result = main.run_passes(passes.as_str(), &target_machine, pass_options);
    if let Err(err) = result {
        panic!("Failed to run optimization for module `main`: {}", err.to_string());
    }

    // Write output
    target_machine
        .write_to_file(&main, FileType::Object, Path::new("module.o"))
        .expect("couldn't write module to file");
}