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use std::collections::HashMap;
use base::symbol::Symbol;
use base::types;
use base::types::{Alias, KindEnv, TypeEnv, TcType, Type};

pub use self::Instruction::*;

pub type VMIndex = u32;
pub type VMTag = u32;
pub type VMInt = isize;

#[derive(Copy, Clone, Debug)]
pub enum Instruction {
    PushInt(isize),
    PushByte(u8),
    PushFloat(f64),
    PushString(VMIndex),
    Push(VMIndex),
    PushGlobal(VMIndex),
    Call(VMIndex),
    TailCall(VMIndex),
    Construct(VMIndex, VMIndex),
    ConstructArray(VMIndex),
    GetField(VMIndex),
    Split,
    TestTag(VMTag),
    Jump(VMIndex),
    CJump(VMIndex),
    Pop(VMIndex),
    Slide(VMIndex),

    // Creates a closure with 'n' upvariables
    // Pops the 'n' values on top of the stack and creates a closure
    MakeClosure(VMIndex, VMIndex),
    // Creates a closure but does not fill its environment
    NewClosure(VMIndex, VMIndex),
    // Fills the previously allocated closure with `n` upvariables
    CloseClosure(VMIndex),
    PushUpVar(VMIndex),

    GetIndex,

    AddInt,
    SubtractInt,
    MultiplyInt,
    DivideInt,
    IntLT,
    IntEQ,

    AddByte,
    SubtractByte,
    MultiplyByte,
    DivideByte,
    ByteLT,
    ByteEQ,

    AddFloat,
    SubtractFloat,
    MultiplyFloat,
    DivideFloat,
    FloatLT,
    FloatEQ,
}


impl Instruction {
    pub fn adjust(&self) -> i32 {
        match *self {
            PushInt(_) | PushByte(_) | PushFloat(_) | PushString(_) | Push(_) | PushGlobal(_) => 1,
            Call(n) => -(n as i32),
            TailCall(n) => -(n as i32),
            Construct(_, n) |
            ConstructArray(n) => 1 - n as i32,
            GetField(_) => 0,
            // The number of added stack slots are handled separately as the type is needed to
            // calculate the number of slots needed
            Split => -1,
            TestTag(_) => 1,
            Jump(_) => 0,
            CJump(_) => -1,
            Pop(n) => -(n as i32),
            Slide(n) => -(n as i32),
            MakeClosure(_, _) => 1,
            NewClosure(_, _) => 1,
            CloseClosure(_) => -1,
            PushUpVar(_) => 1,
            GetIndex => 0,
            AddInt | SubtractInt | MultiplyInt | DivideInt | IntLT | IntEQ | AddFloat |
            AddByte | SubtractByte | MultiplyByte | DivideByte | ByteLT | ByteEQ |
            SubtractFloat | MultiplyFloat | DivideFloat | FloatLT | FloatEQ => -1,
        }
    }
}

#[derive(Debug)]
pub struct TypeInfos {
    pub id_to_type: HashMap<String, Alias<Symbol, TcType>>,
    pub type_to_id: HashMap<TcType, TcType>,
}

impl KindEnv for TypeInfos {
    fn find_kind(&self, type_name: &Symbol) -> Option<types::RcKind> {
        let type_name = AsRef::<str>::as_ref(type_name);
        self.id_to_type
            .get(type_name)
            .map(|alias| {
                alias.args.iter().rev().fold(types::Kind::star(), |acc, arg| {
                    types::Kind::function(arg.kind.clone(), acc)
                })
            })
    }
}

impl TypeEnv for TypeInfos {
    fn find_type(&self, id: &Symbol) -> Option<&TcType> {
        let id = AsRef::<str>::as_ref(id);
        self.id_to_type
            .iter()
            .filter_map(|(_, ref alias)| {
                alias.typ.as_ref().and_then(|typ| {
                    match **typ {
                        Type::Variants(ref variants) => {
                            variants.iter().find(|v| v.0.as_ref() == id)
                        }
                        _ => None,
                    }
                })
            })
            .next()
            .map(|x| &x.1)
    }

    fn find_type_info(&self, id: &Symbol) -> Option<&Alias<Symbol, TcType>> {
        let id = AsRef::<str>::as_ref(id);
        self.id_to_type
            .get(id)
    }

    fn find_record(&self, fields: &[Symbol]) -> Option<(&TcType, &TcType)> {
        self.id_to_type
            .iter()
            .find(|&(_, alias)| {
                alias.typ
                     .as_ref()
                     .map(|typ| {
                         match **typ {
                             Type::Record { fields: ref record_fields, .. } => {
                                 fields.iter().all(|name| {
                                     record_fields.iter().any(|f| f.name.as_ref() == name.as_ref())
                                 })
                             }
                             _ => false,
                         }
                     })
                     .unwrap_or(false)
            })
            .and_then(|t| {
                let typ = t.1.typ.as_ref().unwrap();
                self.type_to_id.get(typ).map(|id_type| (id_type, typ))
            })
    }
}

impl TypeInfos {
    pub fn new() -> TypeInfos {
        TypeInfos {
            id_to_type: HashMap::new(),
            type_to_id: HashMap::new(),
        }
    }

    pub fn extend(&mut self, other: TypeInfos) {
        let TypeInfos { id_to_type, type_to_id } = other;
        self.id_to_type.extend(id_to_type);
        self.type_to_id.extend(type_to_id);
    }
}