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

use eframe::egui;
use parking_lot::{Mutex, RwLock};

use nac3core::codegen;
use nac3core::inkwell;
use nac3core::nac3parser;
use nac3core::toplevel;
use nac3core::toplevel::composer;
use nac3core::typecheck::{type_inferencer, typedef};

mod basic_symbol_resolver;
use basic_symbol_resolver::{Resolver, ResolverInternal};

fn handle_typevar_definition(
    var: &nac3parser::ast::Expr,
    resolver: &(dyn nac3core::symbol_resolver::SymbolResolver + Send + Sync),
    def_list: &[Arc<RwLock<toplevel::TopLevelDef>>],
    unifier: &mut nac3core::typecheck::typedef::Unifier,
    primitives: &type_inferencer::PrimitiveStore,
) -> Result<typedef::Type, HashSet<String>> {
    let nac3parser::ast::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 {
        nac3parser::ast::ExprKind::Name { id, .. } if id == &"TypeVar".into() => {
            let nac3parser::ast::ExprKind::Constant {
                value: nac3parser::ast::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: nac3parser::ast::StrRef = ty_name.to_string().into();

            let constraints = args
                .iter()
                .skip(1)
                .map(|x| -> Result<typedef::Type, HashSet<String>> {
                    let ty = toplevel::type_annotation::parse_ast_to_type_annotation_kinds(
                        resolver,
                        def_list,
                        unifier,
                        primitives,
                        x,
                        HashMap::new(),
                    )?;
                    toplevel::type_annotation::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)
        }

        nac3parser::ast::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 nac3parser::ast::ExprKind::Constant {
                value: nac3parser::ast::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: nac3parser::ast::StrRef = ty_name.to_string().into();

            let ty = toplevel::type_annotation::parse_ast_to_type_annotation_kinds(
                resolver,
                def_list,
                unifier,
                primitives,
                &args[1],
                HashMap::new(),
            )?;
            let constraint = toplevel::type_annotation::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: &[nac3parser::ast::Expr],
    value: &nac3parser::ast::Expr,
    resolver: &(dyn nac3core::symbol_resolver::SymbolResolver + Send + Sync),
    internal_resolver: &ResolverInternal,
    def_list: &[Arc<RwLock<toplevel::TopLevelDef>>],
    unifier: &mut nac3core::typecheck::typedef::Unifier,
    primitives: &type_inferencer::PrimitiveStore,
) -> Result<(), String> {
    if targets.len() == 1 {
        match &targets[0].node {
            nac3parser::ast::ExprKind::Name { id, .. } => {
                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) =
                    toplevel::helper::parse_parameter_default_value(value, resolver)
                {
                    internal_resolver.add_module_global(*id, val);
                    Ok(())
                } else {
                    Err(format!("fails to evaluate this expression `{:?}` as a constant or generic parameter at {}",
                        targets[0].node,
                        targets[0].location,
                    ))
                }
            }
            nac3parser::ast::ExprKind::List { elts, .. }
            | nac3parser::ast::ExprKind::Tuple { elts, .. } => {
                handle_assignment_pattern(
                    elts,
                    value,
                    resolver,
                    internal_resolver,
                    def_list,
                    unifier,
                    primitives,
                )?;
                Ok(())
            }
            _ => Err(format!(
                "assignment to {:?} is not supported at {}",
                targets[0], targets[0].location
            )),
        }
    } else {
        match &value.node {
            nac3parser::ast::ExprKind::List { elts, .. }
            | nac3parser::ast::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,
                            internal_resolver,
                            def_list,
                            unifier,
                            primitives,
                        )?;
                    }
                    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: &nac3parser::ast::Expr,
    value: Option<&nac3parser::ast::Expr>,
    resolver: &(dyn nac3core::symbol_resolver::SymbolResolver + Send + Sync),
    internal_resolver: &ResolverInternal,
) -> Result<(), String> {
    let nac3parser::ast::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) = toplevel::helper::parse_parameter_default_value(value, resolver) {
        internal_resolver.add_module_global(id, val);
        Ok(())
    } else {
        Err(format!(
            "failed to evaluate this expression `{:?}` as a constant at {}",
            target.node, target.location,
        ))
    }
}

fn register_cells_function(
    composer: &mut composer::TopLevelComposer,
    resolver: Arc<dyn nac3core::symbol_resolver::SymbolResolver + Send + Sync>,
    internal_resolver: &ResolverInternal,
    name: &str,
    signature: typedef::FunSignature,
) {
    let ty = composer.unifier.add_ty(typedef::TypeEnum::TFunc(signature));
    let name_ref = name.into();
    let mut function_def = composer::TopLevelComposer::make_top_level_function_def(
        name.to_string(),
        name_ref,
        ty,
        Some(resolver.clone()),
        None,
    );
    if let toplevel::TopLevelDef::Function {
        ref mut instance_to_symbol,
        ..
    } = function_def
    {
        instance_to_symbol.insert("".to_string(), "__nac3_cells_".to_string() + name);
    } else {
        unreachable!();
    };
    composer
        .definition_ast_list
        .push((RwLock::new(function_def).into(), None));
    internal_resolver.add_id_def(
        name_ref,
        toplevel::DefinitionId(composer.definition_ast_list.len() - 1),
    );
    internal_resolver.add_id_type(name_ref, ty);
}

fn compile(code: &String, run_symbol: &String, output_filename: &Path) -> Result<(), String> {
    let mut target_machine_options = codegen::CodeGenTargetMachineOptions::from_host();
    target_machine_options.reloc_mode = inkwell::targets::RelocMode::PIC;
    let llvm_options = codegen::CodeGenLLVMOptions {
        opt_level: inkwell::OptimizationLevel::Default,
        target: target_machine_options,
    };
    let context = inkwell::context::Context::create();
    let target_machine = llvm_options
        .target
        .create_target_machine(llvm_options.opt_level)
        .expect("couldn't create target machine");
    let size_t = context
        .ptr_sized_int_type(&target_machine.get_target_data(), None)
        .get_bit_width();
    let primitive: type_inferencer::PrimitiveStore =
        composer::TopLevelComposer::make_primitives(size_t).0;
    let (mut composer, builtins_def, builtins_ty) = composer::TopLevelComposer::new(
        vec![],
        vec![],
        composer::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 nac3core::symbol_resolver::SymbolResolver + Send + Sync>;
    let irrt = codegen::irrt::load_irrt(&context, resolver.as_ref());

    let list_tvar = if let typedef::TypeEnum::TObj { params, .. } =
        &*composer.unifier.get_ty_immutable(primitive.list)
    {
        typedef::iter_type_vars(params).nth(0).unwrap()
    } else {
        unreachable!()
    };
    let list_float = composer
        .unifier
        .subst(
            primitive.list,
            &typedef::into_var_map([typedef::TypeVar {
                id: list_tvar.id,
                ty: primitive.float,
            }]),
        )
        .unwrap();
    register_cells_function(
        &mut composer,
        resolver.clone(),
        internal_resolver.as_ref(),
        "slider",
        typedef::FunSignature {
            args: vec![typedef::FuncArg {
                name: "prev".into(),
                ty: primitive.float,
                default_value: None,
                is_vararg: false,
            }],
            ret: primitive.float,
            vars: typedef::VarMap::new(),
        },
    );
    register_cells_function(
        &mut composer,
        resolver.clone(),
        internal_resolver.as_ref(),
        "plot",
        typedef::FunSignature {
            args: vec![typedef::FuncArg {
                name: "data".into(),
                ty: list_float,
                default_value: None,
                is_vararg: false,
            }],
            ret: primitive.none,
            vars: typedef::VarMap::new(),
        },
    );

    let parser_result =
        match nac3parser::parser::parse_program(code.as_str(), String::from("cell1").into()) {
            Ok(parser_result) => parser_result,
            Err(err) => {
                return Err(format!("parse error: {}", err));
            }
        };
    for mut stmt in parser_result {
        match stmt.node {
            nac3parser::ast::StmtKind::Assign { targets, value, .. } => {
                let def_list = composer.extract_def_list();
                let unifier = &mut composer.unifier;
                let primitives = &composer.primitives_ty;
                handle_assignment_pattern(
                    &targets,
                    &value,
                    resolver.as_ref(),
                    internal_resolver.as_ref(),
                    &def_list,
                    unifier,
                    primitives,
                )?;
            }
            nac3parser::ast::StmtKind::AnnAssign {
                ref target,
                ref value,
                ..
            } => {
                handle_global_var(
                    &target,
                    value.as_ref().map(Box::as_ref),
                    resolver.as_ref(),
                    internal_resolver.as_ref(),
                )?;

                let (name, def_id, _) = composer
                    .register_top_level(stmt, Some(resolver.clone()), "__main__", true)
                    .unwrap();
                internal_resolver.add_id_def(name, def_id);
            }
            _ => {
                if let nac3parser::ast::StmtKind::FunctionDef { name, .. } = &mut stmt.node {
                    if name.to_string() == "run" {
                        *name = run_symbol.as_str().into();
                    }
                }
                match composer.register_top_level(stmt, Some(resolver.clone()), "__main__", true) {
                    Ok((name, def_id, ty)) => {
                        internal_resolver.add_id_def(name, def_id);
                        if let Some(ty) = ty {
                            internal_resolver.add_id_type(name, ty);
                        }
                    }
                    Err(err) => {
                        return Err(format!("composer error: {}", err));
                    }
                }
            }
        }
    }

    let signature = typedef::FunSignature {
        args: vec![],
        ret: primitive.none,
        vars: typedef::VarMap::new(),
    };
    let mut store = codegen::concrete_type::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();
        let mut msg = format!("{error_count} error(s) occurred during top level analysis.");

        for (error_i, error) in errors.iter().enumerate() {
            let error_num = error_i + 1;
            msg.push_str(&format!(
                "\n=========== ERROR {error_num}/{error_count} ============\n{error}"
            ));
        }
        return Err(msg);
    }

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

    let run_id_def = match resolver.get_identifier_def(run_symbol.as_str().into()) {
        Ok(run_id_def) => run_id_def,
        Err(_) => {
            return Err(format!("no run() entry point"));
        }
    };
    let instance = {
        let defs = top_level.definitions.read();
        let mut instance = defs[run_id_def.0].write();
        let toplevel::TopLevelDef::Function {
            instance_to_stmt,
            instance_to_symbol,
            ..
        } = &mut *instance
        else {
            unreachable!()
        };
        instance_to_symbol.insert(String::new(), run_symbol.clone());
        instance_to_stmt[""].clone()
    };

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

    let nthreads = if inkwell::support::is_multithreaded() {
        std::thread::available_parallelism()
            .map(NonZeroUsize::get)
            .unwrap_or(1usize)
    } else {
        1
    };

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

    let f = Arc::new(codegen::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..nthreads)
        .map(|i| {
            Box::new(codegen::DefaultCodeGenerator::new(
                format!("module{i}"),
                size_t,
            ))
        })
        .collect();
    let (registry, handles) =
        codegen::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(
            inkwell::memory_buffer::MemoryBuffer::create_from_memory_range(&buffers[0], "main"),
        )
        .unwrap();
    for buffer in buffers.iter().skip(1) {
        let other = context
            .create_module_from_ir(
                inkwell::memory_buffer::MemoryBuffer::create_from_memory_range(buffer, "main"),
            )
            .unwrap();
        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_symbol {
            func.set_linkage(inkwell::module::Linkage::Private);
        }
        function_iter = func.get_next_function();
    }

    let pass_options = inkwell::passes::PassBuilderOptions::create();
    pass_options.set_merge_functions(true);
    main.run_passes("default<O2>", &target_machine, pass_options)
        .unwrap();

    target_machine
        .write_to_file(&main, inkwell::targets::FileType::Object, output_filename)
        .unwrap();
    Ok(())
}

// The year is 2024, and compiler toolchains are still a trash fire.
fn link_with_lld(elf_filename: &Path, obj_filename: &Path) -> Result<(), String> {
    let linker_args = vec![
        "-shared".to_string(),
        "--eh-frame-hdr".to_string(),
        "-x".to_string(),
        "-o".to_string(),
        elf_filename.to_str().unwrap().to_string(),
        obj_filename.to_str().unwrap().to_string(),
    ];

    if let Ok(linker_status) = Command::new("ld.lld").args(linker_args).status() {
        if !linker_status.success() {
            return Err("failed to start linker".to_string());
        }
    } else {
        return Err("linker returned non-zero status code".to_string());
    }

    Ok(())
}

type RunFn = unsafe extern "C" fn();

struct CellBin {
    cell_id: usize,
    // note destructor order
    run_fn: Option<RunFn>,
    library: Option<libloading::Library>,
    directory: tempfile::TempDir,
}

impl CellBin {
    fn new(cell_id: usize) -> Self {
        Self {
            cell_id,
            run_fn: None,
            library: None,
            directory: tempfile::tempdir().unwrap(),
        }
    }

    fn compile_and_load(&mut self, code: &String) -> Result<(), String> {
        assert!(self.run_fn.is_none());
        assert!(self.library.is_none());
        let object = self.directory.path().join("module.o");
        let library = self.directory.path().join("module.so");
        let run_symbol = format!("__cells_run_{}", self.cell_id);
        compile(code, &run_symbol, &object)?;
        link_with_lld(&library, &object)?;
        unsafe {
            self.library = Some(libloading::Library::new(library).or_else(|e| Err(e.to_string()))?);
            let raw_fun_ptr = self
                .library
                .as_ref()
                .unwrap()
                .get::<RunFn>(run_symbol.as_bytes())
                .unwrap()
                .try_as_raw_ptr()
                .unwrap();
            self.run_fn = Some(std::mem::transmute(raw_fun_ptr));
        }
        Ok(())
    }
}

struct Cell {
    code: String,
    result: Result<CellBin, String>,
}

impl Cell {
    const DEFAULT_CODE: &'static str = "def run():\n    pass";

    fn new() -> Self {
        Self {
            code: Self::DEFAULT_CODE.to_string(),
            result: Err("".to_string()),
        }
    }

    fn is_default(&self) -> bool {
        self.code == Self::DEFAULT_CODE
    }

    fn update(&mut self) {
        let mut new_bin = CellBin::new(0usize);
        self.result = new_bin
            .compile_and_load(&self.code)
            .and_then(|_| Ok(new_bin));
    }
}

struct Cells {
    cells: Vec<Cell>,
}

static mut CELL_UI: Option<&'static mut egui::Ui> = None;

#[no_mangle]
pub extern "C" fn __nac3_cells_slider(prev: f64) -> f64 {
    let ui = unsafe { CELL_UI.as_mut().unwrap() };
    let mut value = prev;
    ui.add(egui::Slider::new(&mut value, 0.0..=100.0));
    value
}

pub struct List {
    data: *mut f64,
    length: usize,
}

#[no_mangle]
pub extern "C" fn __nac3_cells_plot(data: *const List) {
    let ui = unsafe { CELL_UI.as_mut().unwrap() };
    let data_slice = unsafe { std::slice::from_raw_parts((*data).data, (*data).length) };
    let points: Vec<[f64; 2]> = (0..data_slice.len())
        .map(|i| [i as f64, data_slice[i]])
        .collect();
    let line = egui_plot::Line::new(points);
    egui_plot::Plot::new("my_plot")
        .view_aspect(2.0)
        .show(ui, |plot_ui| plot_ui.line(line));
}

impl Cells {
    fn new() -> Self {
        Self {
            cells: vec![Cell::new()],
        }
    }

    fn update(&mut self) {
        for cell in self.cells.iter_mut() {
            cell.update()
        }
    }

    fn ensure_last(&mut self) {
        let last_cell = self.cells.last().unwrap();
        if last_cell.result.is_ok() && !last_cell.is_default() {
            self.cells.push(Cell::new());
        }
    }

    fn ui(&mut self, ui: &mut egui::Ui) {
        for (cell_i, cell) in self.cells.iter_mut().enumerate() {
            let theme = egui_extras::syntax_highlighting::CodeTheme::from_memory(ui.ctx());
            let mut layouter = |ui: &egui::Ui, string: &str, wrap_width: f32| {
                let mut layout_job =
                    egui_extras::syntax_highlighting::highlight(ui.ctx(), &theme, string, "Python");
                layout_job.wrap.max_width = wrap_width;
                layout_job.sections = layout_job
                    .sections
                    .iter()
                    .map(|layout_section| {
                        let mut section = layout_section.clone();
                        section.format.font_id = egui::FontId::monospace(16.0);
                        section
                    })
                    .collect();
                ui.fonts(|f| f.layout_job(layout_job))
            };
            ui.group(|ui| {
                ui.horizontal(|ui| {
                    ui.label(format!("[{}]", cell_i));
                    ui.add(
                        egui::TextEdit::multiline(&mut cell.code)
                            .code_editor()
                            .desired_rows(4)
                            .lock_focus(true)
                            .desired_width(f32::INFINITY)
                            .layouter(&mut layouter)
                            .font(egui::FontId::monospace(16.0)),
                    );
                });
                match &cell.result {
                    Ok(bin) => unsafe {
                        CELL_UI.replace(
                            std::mem::transmute::<&mut egui::Ui, &'static mut egui::Ui>(ui),
                        );
                        bin.run_fn.unwrap()();
                        CELL_UI.take();
                    },
                    Err(msg) => {
                        if !msg.is_empty() {
                            ui.colored_label(egui::Color32::from_rgb(255, 0, 0), msg);
                        }
                    }
                };
            });
        }
    }
}

fn main() -> eframe::Result {
    inkwell::targets::Target::initialize_native(&inkwell::targets::InitializationConfig::default())
        .unwrap();

    let options = eframe::NativeOptions {
        viewport: egui::ViewportBuilder::default().with_inner_size([1024.0, 768.0]),
        ..Default::default()
    };

    let mut cells = Cells::new();

    eframe::run_simple_native("Cells", options, move |ctx, _frame| {
        let submit_key = egui::KeyboardShortcut::new(egui::Modifiers::CTRL, egui::Key::Enter);
        if ctx.input_mut(|input| input.consume_shortcut(&submit_key)) {
            cells.update();
            cells.ensure_last();
        }

        egui::CentralPanel::default().show(ctx, |ui| {
            cells.ui(ui);
        });
    })
}

#[no_mangle]
pub extern "C" fn __nac3_personality(_state: u32, _exception_object: u32, _context: u32) -> u32 {
    unimplemented!()
}