using System;
using System.Collections.Generic;
using System.Linq;

namespace ABT {
    //public enum StmtKind {
    //    GOTO,
    //    LABELED,
    //    CONT,
    //    BREAK,
    //    EXPR,
    //    COMPOUND,
    //    RETURN,
    //    WHILE,
    //    DO,
    //    FOR,
    //    SWITCH,
    //    CASE,
    //    DEFAULT,
    //    IF,
    //    IF_ELSE
    //}

    public abstract partial class Stmt {
        public Env Env { get; }

        public abstract void Accept(StmtVisitor visitor);

        public virtual bool IsJump { get => false; }
    }

    /// <summary>
    /// Goto Statement
    /// </summary>
    public sealed partial class GotoStmt : Stmt {
        public GotoStmt(String label) {
            this.Label = label;
        }

        public String Label { get; }

        public override void Accept(StmtVisitor visitor) {
            visitor.Visit(this);
        }

        public override bool IsJump => true;
    }

    /// <summary>
    /// Labeled Statement
    /// </summary>
    public sealed partial class LabeledStmt : Stmt {
        public LabeledStmt(String label, Stmt stmt) {
            this.Label = label;
            this.Stmt = stmt;
        }

        public String Label { get; }

        public Stmt Stmt { get; }

        public override void Accept(StmtVisitor visitor) {
            visitor.Visit(this);
        }

        public override bool IsJump => Stmt.IsJump;
    }

    /// <summary>
    /// Continue Statement
    /// </summary>
    public sealed partial class ContStmt : Stmt {
        public override void Accept(StmtVisitor visitor) {
            visitor.Visit(this);
        }

        public override bool IsJump => true;
    }

    /// <summary>
    /// Break Statement
    /// </summary>
    public sealed partial class BreakStmt : Stmt {
        public override void Accept(StmtVisitor visitor) {
            visitor.Visit(this);
        }

        public override bool IsJump => true;
    }

    /// <summary>
    /// Expression Statement
    /// </summary>
    public sealed partial class ExprStmt : Stmt {
        public ExprStmt(Option<Expr> exprOpt) {
            this.ExprOpt = exprOpt;
        }

        public Option<Expr> ExprOpt { get; }

        public override void Accept(StmtVisitor visitor) {
            visitor.Visit(this);
        }

        public override bool IsJump => false;
    }

    public sealed partial class CompoundStmt : Stmt {
        public CompoundStmt(List<Tuple<Env, Decln>> declns, List<Tuple<Env, Stmt>> stmts) {
            this.Declns = declns;
            this.Stmts = stmts;
        }

        public List<Tuple<Env, Decln>> Declns { get; }

        public List<Tuple<Env, Stmt>> Stmts { get; }

        public override void Accept(StmtVisitor visitor) {
            visitor.Visit(this);
        }

        public override bool IsJump => Declns.Count == 0 && Stmts.Count >= 1 && Stmts.First().Item2.IsJump;
    }

    public sealed partial class ReturnStmt : Stmt {
        public ReturnStmt(Option<Expr> exprOpt) {
            this.ExprOpt = exprOpt;
        }

        public Option<Expr> ExprOpt { get; }

        public override void Accept(StmtVisitor visitor) {
            visitor.Visit(this);
        }
    }

    /// <summary>
    /// While Statement
    /// 
    /// while (Cond) {
    ///     Body
    /// }
    /// 
    /// Cond must be of scalar Type
    /// </summary>
    // +--> start: continue:
    // |        test Cond
    // |        jz finish --+
    // |        Body        |
    // +------- jmp start   |
    //      finish: <-------+
    // 
    public sealed partial class WhileStmt : Stmt {
        public WhileStmt(Expr cond, Stmt body) {
            if (!cond.Type.IsScalar) {
                throw new InvalidProgramException().Attach(cond);
            }
            this.Cond = cond;
            this.Body = body;
        }

        public Expr Cond { get; }

        public Stmt Body { get; }

        public override void Accept(StmtVisitor visitor) {
            visitor.Visit(this);
        }
    }

    /// <summary>
    /// Do-while Stmt
    /// 
    /// do {
    ///     Body
    /// } while (Cond);
    /// 
    /// Cond must be of scalar Type
    /// </summary>
    // +--> start:
    // |        Body
    // |    continue:
    // |        test Cond
    // +------- jnz start
    //      finish:
    public sealed partial class DoWhileStmt : Stmt {
        public DoWhileStmt(Stmt body, Expr cond) {
            this.Body = body;
            this.Cond = cond;
        }

        public Stmt Body { get; }

        public Expr Cond { get; }

        public override void Accept(StmtVisitor visitor) {
            visitor.Visit(this);
        }

        public override bool IsJump => Body.IsJump;
    }

    /// <summary>
    /// for (Init; Cond; Loop) {
    ///     Body
    /// }
    /// 
    /// Cond must be scalar
    /// </summary>
    // 
    //          Init
    // +--> start:
    // |        test Cond
    // |        jz finish --+
    // |        Body        |
    // |    continue:       |
    // |        Loop        |
    // +------- jmp start   |
    //      finish: <-------+
    // 
    public sealed partial class ForStmt : Stmt {
        public ForStmt(Option<Expr> init, Option<Expr> cond, Option<Expr> loop, Stmt body) {
            this.Init = init;
            this.Cond = cond;
            this.Loop = loop;
            this.Body = body;
        }

        public Option<Expr> Init { get; }

        public Option<Expr> Cond { get; }

        public Option<Expr> Loop { get; }

        public Stmt Body { get; }

        public override void Accept(StmtVisitor visitor) {
            visitor.Visit(this);
        }
    }

    /// <summary>
    /// Switch Statement
    /// </summary>
    //
    //     cmp Cond, value1
    //     je case1
    //     cmp Cond, value2
    //     je case2
    //     ...
    //     cmp Cond, value_n
    //     je case_n
    //     jmp default # if no default, then default = finish
    //     
    // case1:
    //     stmt
    // case2:
    //     stmt
    // ...
    // case_n:
    //     stmt
    // finish:
    public sealed partial class SwitchStmt : Stmt {
        public SwitchStmt(Expr expr, Stmt stmt) {
            this.Expr = expr;
            this.Stmt = stmt;
        }

        public Expr Expr { get; }

        public Stmt Stmt { get; }

        public override void Accept(StmtVisitor visitor) {
            visitor.Visit(this);
        }
    }

    /// <summary>
    /// Case Statement
    /// </summary>
    public sealed partial class CaseStmt : Stmt {
        public CaseStmt(Int32 value, Stmt stmt) {
            this.Value = value;
            this.Stmt = stmt;
        }

        public Int32 Value { get; }

        public Stmt Stmt { get; }

        public override void Accept(StmtVisitor visitor) {
            visitor.Visit(this);
        }

        public override bool IsJump => Stmt.IsJump;
    }

    public sealed partial class DefaultStmt : Stmt {
        public DefaultStmt(Stmt stmt) {
            this.Stmt = stmt;
        }

        public Stmt Stmt { get; }

        public override void Accept(StmtVisitor visitor) {
            visitor.Visit(this);
        }

        public override bool IsJump => Stmt.IsJump;
    }

    /// <summary>
    /// If Statement: if (Cond) stmt;
    /// If Cond is non-zero, stmt is executed.
    /// 
    /// Cond must be arithmetic or pointer Type.
    /// </summary>
    //          test Cond
    // +------- jz finish
    // |        Body
    // +--> finish:
    public sealed partial class IfStmt : Stmt {
        public IfStmt(Expr cond, Stmt stmt) {
            this.Cond = cond;
            this.Stmt = stmt;
        }

        public Expr Cond { get; }

        public Stmt Stmt { get; }

        public override void Accept(StmtVisitor visitor) {
            visitor.Visit(this);
        }
    }

    /// <summary>
    /// If-else Statement
    /// if (Cond) {
    ///     true_stmt
    /// } else {
    ///     false_stmt
    /// }
    /// </summary>
    ///
    //          test Cond
    // +------- jz false
    // |        true_stmt
    // |        jmp finish --+
    // +--> false:           |
    //          false_stmt   |
    //      finish: <--------+
    // 
    public sealed partial class IfElseStmt : Stmt {
        public IfElseStmt(Expr cond, Stmt trueStmt, Stmt falseStmt) {
            this.Cond = cond;
            this.TrueStmt = trueStmt;
            this.FalseStmt = falseStmt;
        }

        public Expr Cond { get; }

        public Stmt TrueStmt { get; }

        public Stmt FalseStmt { get; }

        public override void Accept(StmtVisitor visitor) {
            visitor.Visit(this);
        }
    }
}