use {
    crate::expr::LTExpr,
    std::{
        collections::HashMap,
        sync::{Arc, RwLock},
    },
    tisc::linker::LinkAddr,
};

#[derive(Clone, Debug)]
pub enum SymbolDef {
    FrameRef {
        typ: laddertypes::TypeTerm,
        stack_ref: tisc::VM_Word,
    },
    StaticRef {
        typ: laddertypes::TypeTerm,
        link_addr: Option<tisc::VM_Word>,
    },
    Procedure {
        in_types: Vec<laddertypes::TypeTerm>,
        out_types: Vec<laddertypes::TypeTerm>,
        link_addr: LinkAddr,
        export: bool
    },
}

impl SymbolDef {
    pub fn get_type(
        &self,
        typectx: &Arc<RwLock<laddertypes::dict::TypeDict>>,
    ) -> laddertypes::TypeTerm {
        match self {
            SymbolDef::FrameRef { typ, stack_ref: _ } => typ.clone(),
            SymbolDef::StaticRef { typ, link_addr: _ } => typ.clone(),
            SymbolDef::Procedure {
                in_types,
                out_types,
                link_addr: _,
                export: _,
            } => laddertypes::TypeTerm::App(vec![
                typectx
                    .write()
                    .unwrap()
                    .parse("Fn")
                    .expect("parse typeterm"),
                laddertypes::TypeTerm::App(in_types.clone()),
                laddertypes::TypeTerm::App(out_types.clone()),
            ]),
        }
    }
}

/* Describes a lexical scope of symbols
 */
pub struct Scope {
    /* definition of runtime symbols
     */
    symbols: HashMap<String, SymbolDef>,

    /* type symbols
     */
    pub typectx: Arc<RwLock<laddertypes::TypeDict>>,

    /* number of words required for
     * the stack frame of this scope
     */
    frame_size: usize,

    /* parent scope whose all
     * symbols are inherited
     */
    parent: Option<Arc<RwLock<Scope>>>,
}

impl Scope {
    pub fn new() -> Arc<RwLock<Self>> {
        Arc::new(RwLock::new(Scope {
            symbols: HashMap::new(),
            typectx: Arc::new(RwLock::new(laddertypes::dict::TypeDict::new())),
            frame_size: 0,
            parent: None,
        }))
    }

    pub fn with_parent(parent: &Arc<RwLock<Scope>>) -> Arc<RwLock<Self>> {
        let s = Scope {
            symbols: HashMap::new(),

            // todo: create proper child scope
            typectx: parent.read().unwrap().typectx.clone(),

            frame_size: 0,
            parent: Some(parent.clone()),
        };

        Arc::new(RwLock::new(s))
    }

    pub fn export(self) -> Vec<(String, SymbolDef)> {
        self.symbols
            .into_iter()
            .filter(|(name, def)|
                match def {
                    SymbolDef::Procedure { in_types:_, out_types:_, link_addr:_, export } => *export,
                    _ => false
                }
            )
            .collect()
    }

    pub fn import(&mut self, symbol_imports: Vec<(String, SymbolDef)>) {
        for (name, def) in symbol_imports {
            self.symbols.insert( name, def );
        }
    }

    pub fn get_frame_size(&self) -> usize {
        self.frame_size
    }

    pub fn get(&self, name: &str) -> Option<SymbolDef> {
        match self.symbols.get(name) {
            Some(def) => Some(def.clone()),
            None => {
                if let Some(parent) = self.parent.as_ref() {
                    match parent.read().unwrap().get(name) {
                        Some(SymbolDef::FrameRef { typ, stack_ref }) => Some(SymbolDef::FrameRef {
                            typ: typ.clone(),
                            stack_ref: stack_ref + self.get_frame_size() as i64,
                        }),
                        x => x.clone(),
                    }
                } else {
                    None
                }
            }
        }
    }

    /// takes the link-addresses from a Linker
    /// and updates the symbol table to relative addresses
    /// based on the next super-label
    pub fn update_link_addresses(
        &mut self,
        base_symbol: &String,
        linker: &tisc::Linker
    ) {
        for (name, def) in self.symbols.iter_mut() {
            if let Some(offset) = linker.get_link_addr( name ) {
                match def {
                    SymbolDef::Procedure {
                        in_types:_,out_types:_,
                        link_addr,
                        export:_
                    } => {
                        *link_addr = LinkAddr::Relative{
                            symbol: base_symbol.clone(),
                            offset
                        };
                    },
                    _ => {}
                }
            }
        }        
    }

    
    //<><><><><><>

    pub fn declare_proc_parse(
        &mut self,
        name: &str,
        type_vars: Vec<&str>,
        in_types: Vec<&str>,
        out_types: Vec<&str>,
    ) {
        for v in type_vars {
            self.typectx.write().unwrap().add_varname(v.into());
        }

        self.declare_proc(
            String::from(name),
            in_types
                .into_iter()
                .map(|t| {
                    self.typectx
                        .write()
                        .unwrap()
                        .parse(t)
                        .expect("parse typeterm")
                })
                .collect(),
            out_types
                .into_iter()
                .map(|t| {
                    self.typectx
                        .write()
                        .unwrap()
                        .parse(t)
                        .expect("parse typeterm")
                })
                .collect(),
            false
        );
    }

    pub fn declare_proc(
        &mut self,
        name: String,
        in_types: Vec<laddertypes::TypeTerm>,
        out_types: Vec<laddertypes::TypeTerm>,
        export: bool
    ) {
        self.symbols.insert(
            name.clone(),
            SymbolDef::Procedure {
                link_addr: LinkAddr::Relative{ symbol: name, offset: 0 },
                in_types,
                out_types,
                export
            },
        );
    }

    //<><><><><>

    pub fn declare_var_parse(&mut self, name: &str, typ: &str) {
        let typ = self
            .typectx
            .write()
            .unwrap()
            .parse(typ)
            .expect("parse typeterm");
        self.declare_var(String::from(name), typ);
    }

    pub fn declare_var(&mut self, name: String, typ: laddertypes::TypeTerm) -> tisc::VM_Word {
        let stack_ref = self.frame_size as tisc::VM_Word;
        self.frame_size += 1;

        self.symbols
            .insert(name, SymbolDef::FrameRef { typ, stack_ref });

        stack_ref
    }

    //<><><><><><>

    pub fn declare_static_parse(&mut self, name: &str, typ: &str) {
        let typ = self
            .typectx
            .write()
            .unwrap()
            .parse(typ)
            .expect("parse typeterm");
        self.declare_static(String::from(name), typ);
    }

    pub fn declare_static(&mut self, name: String, typ: laddertypes::TypeTerm) {
        self.symbols.insert(
            name,
            SymbolDef::StaticRef {
                typ,
                link_addr: None,
            },
        );
    }
}