use std::borrow::Borrow;
use std::fmt;
use std::hash::Hash;

use erg_common::config::ErgConfig;
use erg_common::dict::Dict;
use erg_common::levenshtein::get_similar_name;
use erg_common::pathutil::NormalizedPathBuf;
use erg_common::shared::{
    MappedRwLockReadGuard, MappedRwLockWriteGuard, RwLockReadGuard, RwLockWriteGuard, Shared,
};
use erg_common::spawn::safe_yield;
use erg_common::Str;
use erg_parser::ast::Module;

use crate::build_package::CheckStatus;
use crate::context::ModuleContext;
use crate::hir::HIR;
use crate::ty::free::FreeTyVar;

#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
pub struct ModId(usize);

impl ModId {
    pub const fn new(id: usize) -> Self {
        Self(id)
    }
    pub const fn builtin() -> Self {
        Self(0)
    }
    pub const fn main() -> Self {
        Self(1)
    }
}

#[derive(Debug, Clone)]
pub struct ModuleEntry {
    pub id: ModId, // builtin == 0, __main__ == 1
    /// mainly for ELS
    pub ast: Option<Module>,
    pub hir: Option<HIR>,
    pub module: ModuleContext,
    pub status: CheckStatus,
}

impl fmt::Display for ModuleEntry {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(
            f,
            "ModuleEntry(id = {}, name = {})",
            self.id.0, self.module.context.name
        )
    }
}

impl ModuleEntry {
    pub const fn new(
        id: ModId,
        ast: Option<Module>,
        hir: Option<HIR>,
        ctx: ModuleContext,
        status: CheckStatus,
    ) -> Self {
        Self {
            id,
            ast,
            hir,
            module: ctx,
            status,
        }
    }

    pub fn builtin(ctx: ModuleContext) -> Self {
        Self {
            id: ModId::builtin(),
            ast: None,
            hir: None,
            module: ctx,
            status: CheckStatus::Succeed,
        }
    }

    pub const fn cfg(&self) -> &ErgConfig {
        &self.module.context.cfg
    }

    pub const fn is_complete(&self) -> bool {
        self.status.is_succeed() && self.ast.is_some() && self.hir.is_some()
    }
}

/// `IRs = ModuleEntry - ModuleContext`
pub struct IRs {
    pub id: ModId,
    pub ast: Option<Module>,
    pub hir: Option<HIR>,
    pub status: CheckStatus,
}

impl IRs {
    pub const fn new(
        id: ModId,
        ast: Option<Module>,
        hir: Option<HIR>,
        status: CheckStatus,
    ) -> Self {
        Self {
            id,
            ast,
            hir,
            status,
        }
    }
}

/// Caches checked modules.
/// In addition to being queried here when re-imported, it is also used when linking
/// (Erg links all scripts defined in erg and outputs them to a single pyc file).
#[derive(Debug, Default)]
pub struct ModuleCache {
    cache: Dict<NormalizedPathBuf, ModuleEntry>,
    last_id: usize,
}

impl fmt::Display for ModuleCache {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        writeln!(f, "ModuleCache {{")?;
        for (path, entry) in self.cache.iter() {
            writeln!(f, "{}: {}, ", path.display(), entry)?;
        }
        write!(f, "}}")
    }
}

impl ModuleCache {
    pub fn new() -> Self {
        Self {
            cache: Dict::new(),
            last_id: 0,
        }
    }

    pub fn get<P: Eq + Hash + ?Sized>(&self, path: &P) -> Option<&ModuleEntry>
    where
        NormalizedPathBuf: Borrow<P>,
    {
        self.cache.get(path)
    }

    pub fn get_mut<Q: Eq + Hash + ?Sized>(&mut self, path: &Q) -> Option<&mut ModuleEntry>
    where
        NormalizedPathBuf: Borrow<Q>,
    {
        self.cache.get_mut(path)
    }

    pub fn register(
        &mut self,
        path: NormalizedPathBuf,
        ast: Option<Module>,
        hir: Option<HIR>,
        ctx: ModuleContext,
        status: CheckStatus,
    ) {
        self.last_id += 1;
        let id = ModId::new(self.last_id);
        let entry = ModuleEntry::new(id, ast, hir, ctx, status);
        self.cache.insert(path, entry);
    }

    pub fn remove<Q: Eq + Hash + ?Sized>(&mut self, path: &Q) -> Option<ModuleEntry>
    where
        NormalizedPathBuf: Borrow<Q>,
    {
        self.cache.remove(path)
    }

    pub fn remove_by_id(&mut self, id: ModId) -> Option<ModuleEntry> {
        if let Some(name) = self.cache.iter().find_map(|(name, ent)| {
            if ent.id == id {
                Some(name.clone())
            } else {
                None
            }
        }) {
            self.remove(&name)
        } else {
            None
        }
    }

    pub fn get_similar_name(&self, name: &str) -> Option<Str> {
        get_similar_name(
            self.cache
                .iter()
                .map(|(v, _)| v.to_str().unwrap_or_default()),
            name,
        )
        .map(Str::rc)
    }

    pub fn rename_path(&mut self, old: &NormalizedPathBuf, new: NormalizedPathBuf) {
        if let Some(entry) = self.cache.remove(old) {
            self.cache.insert(new, entry);
        }
    }

    pub fn iter(&self) -> impl Iterator<Item = (&NormalizedPathBuf, &ModuleEntry)> {
        self.cache.iter()
    }

    pub fn values(&self) -> impl Iterator<Item = &ModuleEntry> {
        self.cache.values()
    }

    pub fn clear(&mut self) {
        self.cache.clear();
    }
}

#[derive(Debug, Clone, Default)]
pub struct SharedModuleCache(Shared<ModuleCache>);

impl fmt::Display for SharedModuleCache {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        write!(f, "Shared{}", self.0)
    }
}

impl SharedModuleCache {
    pub fn new() -> Self {
        Self(Shared::new(ModuleCache::new()))
    }

    pub fn is_empty(&self) -> bool {
        self.0.borrow().cache.is_empty()
    }

    pub fn len(&self) -> usize {
        self.0.borrow().cache.len()
    }

    pub fn get<Q: Eq + Hash + ?Sized>(&self, path: &Q) -> Option<MappedRwLockReadGuard<ModuleEntry>>
    where
        NormalizedPathBuf: Borrow<Q>,
    {
        if self.0.borrow().get(path).is_some() {
            Some(RwLockReadGuard::map(self.0.borrow(), |cache| {
                cache.get(path).unwrap()
            }))
        } else {
            None
        }
    }

    pub fn get_mut<Q: Eq + Hash + ?Sized>(
        &self,
        path: &Q,
    ) -> Option<MappedRwLockWriteGuard<ModuleEntry>>
    where
        NormalizedPathBuf: Borrow<Q>,
    {
        if self.0.borrow().get(path).is_some() {
            Some(RwLockWriteGuard::map(self.0.borrow_mut(), |cache| {
                cache.get_mut(path).unwrap()
            }))
        } else {
            None
        }
    }

    pub fn ref_ctx<Q: Eq + Hash + ?Sized>(
        &self,
        path: &Q,
    ) -> Option<MappedRwLockReadGuard<ModuleContext>>
    where
        NormalizedPathBuf: Borrow<Q>,
    {
        if self.0.borrow().get(path).is_some() {
            Some(RwLockReadGuard::map(self.0.borrow(), |cache| {
                &cache.get(path).unwrap().module
            }))
        } else {
            None
        }
    }

    /// FIXME: see the comment in this function
    pub fn raw_ref_ctx<Q: Eq + Hash + ?Sized>(&self, path: &Q) -> Option<&ModuleContext>
    where
        NormalizedPathBuf: Borrow<Q>,
    {
        // Check if the module can be borrowed
        // If you delete `_ref`, this function returns `None` even if the key exists in rare cases
        let _ref = self.0.borrow();
        let ref_ = unsafe { self.0.as_ptr().as_ref().unwrap() };
        ref_.get(path).map(|entry| &entry.module)
    }

    pub fn raw_ref_ctx_with_timeout<Q: Eq + Hash + ?Sized>(
        &self,
        path: &Q,
        timeout: std::time::Duration,
    ) -> Option<&ModuleContext>
    where
        NormalizedPathBuf: Borrow<Q>,
    {
        let _ref = self.0.try_borrow_for(timeout)?;
        let ref_ = unsafe { self.0.as_ptr().as_ref().unwrap() };
        ref_.get(path).map(|entry| &entry.module)
    }

    // HACK: <builtins> is referenced very frequently and mutable references are not taken,
    // so it can be take without lock.
    pub fn raw_ref_builtins_ctx(&self) -> Option<&ModuleContext> {
        let ref_ = unsafe { self.0.as_ptr().as_ref().unwrap() };
        ref_.get(std::path::Path::new("<builtins>"))
            .map(|entry| &entry.module)
    }

    pub fn register<P: Into<NormalizedPathBuf>>(
        &self,
        path: P,
        ast: Option<Module>,
        hir: Option<HIR>,
        ctx: ModuleContext,
        status: CheckStatus,
    ) {
        self.0
            .borrow_mut()
            .register(path.into(), ast, hir, ctx, status);
    }

    pub fn insert(&self, path: NormalizedPathBuf, entry: ModuleEntry) {
        self.0.borrow_mut().cache.insert(path, entry);
    }

    pub fn remove<Q: Eq + Hash + ?Sized>(&self, path: &Q) -> Option<ModuleEntry>
    where
        NormalizedPathBuf: Borrow<Q>,
    {
        let mut cache = loop {
            if let Some(cache) = self.0.try_borrow_mut() {
                break cache;
            }
            safe_yield();
        };
        cache.remove(path)
    }

    #[allow(clippy::result_unit_err)]
    pub fn try_remove<Q: Eq + Hash + ?Sized>(&self, path: &Q) -> Result<Option<ModuleEntry>, ()>
    where
        NormalizedPathBuf: Borrow<Q>,
    {
        if let Some(mut lock) = self.0.try_borrow_mut() {
            Ok(lock.remove(path))
        } else {
            Err(())
        }
    }

    pub fn remove_by_id(&self, id: ModId) -> Option<ModuleEntry> {
        self.0.borrow_mut().remove_by_id(id)
    }

    pub fn get_similar_name(&self, name: &str) -> Option<Str> {
        self.0.borrow().get_similar_name(name)
    }

    pub fn initialize(&self) {
        let builtin_path = NormalizedPathBuf::from("<builtins>");
        let Some(builtin) = self.remove(&builtin_path) else {
            return;
        };
        self.0.borrow_mut().clear();
        self.register(
            builtin_path,
            None,
            None,
            builtin.module,
            CheckStatus::Succeed,
        );
    }

    pub fn rename_path<P: Into<NormalizedPathBuf>>(&self, path: &NormalizedPathBuf, new: P) {
        self.0.borrow_mut().rename_path(path, new.into());
    }

    pub fn ref_inner(&self) -> MappedRwLockReadGuard<Dict<NormalizedPathBuf, ModuleEntry>> {
        RwLockReadGuard::map(self.0.borrow(), |mc| &mc.cache)
    }

    pub fn raw_values(&self) -> impl Iterator<Item = &ModuleEntry> {
        let _ref = self.0.borrow();
        let ref_ = unsafe { self.0.as_ptr().as_ref().unwrap() };
        ref_.values()
    }

    pub fn raw_iter(&self) -> impl Iterator<Item = (&NormalizedPathBuf, &ModuleEntry)> {
        let _ref = self.0.borrow();
        let ref_ = unsafe { self.0.as_ptr().as_ref().unwrap() };
        ref_.iter()
    }
}

#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub struct GeneralizationResult {
    pub impl_trait: bool,
    pub is_subtype: bool,
}

#[derive(Debug, Clone, Default)]
pub struct SharedGeneralizationCache(Shared<Dict<FreeTyVar, GeneralizationResult>>);

impl SharedGeneralizationCache {
    pub fn new() -> Self {
        Self(Shared::new(Dict::new()))
    }

    pub fn insert(&self, key: FreeTyVar, res: GeneralizationResult) {
        self.0.borrow_mut().insert(key, res);
    }

    pub fn get(&self, key: &FreeTyVar) -> Option<GeneralizationResult> {
        self.0.borrow().get(key).cloned()
    }
}