use crate::ast::*;
use crate::interp::*;

use anyhow::{bail, Error};

/// The list of builtins provided at startup.
pub fn builtins() -> Vec<BuiltinFunc> {
    vec![
        BuiltinFunc {
            name: "rep",
            callback: Box::new(|state: &State, exprs: &[ExprRef], env: &Env| -> Result<Value, Error> {
                if let [rep, expr] = exprs {
                    let mut buf = String::new();
                    let num = state.eval(*rep, env)?.as_num(&state.ast.borrow())?;
                    for _ in 0..num {
                        buf.push_str(
                            &state
                                .eval(*expr, env)?
                                .as_str(&state.ast.borrow())?
                                .to_string(),
                        );
                    }
                    Ok(Value::Lit(Literal::Str(buf)))
                } else {
                    bail!("`rep`: expected two arguments, got {}", exprs.len())
                }
            }),
        },

        BuiltinFunc {
            name: "str/upper",
            callback: Box::new(|state: &State, exprs: &[ExprRef], env: &Env| -> Result<Value, Error> {
                if let [expr] = exprs {
                    let s = state.eval(*expr, env)?;
                    Ok(Value::Lit(Literal::Str(
                        s.as_str(&state.ast.borrow())?.to_uppercase(),
                    )))
                } else {
                    bail!("`str/capitalize`: expected 1 argument1, got {}", exprs.len());
                }
            }),
        },

        BuiltinFunc {
            name: "str/capitalize",
            callback: Box::new(|state: &State, exprs: &[ExprRef], env: &Env| -> Result<Value, Error> {
                if let [expr] = exprs {
                    let s = state.eval(*expr, env)?;
                    Ok(Value::Lit(Literal::Str(titlecase::titlecase(
                        s.as_str(&state.ast.borrow())?,
                    ))))
                } else {
                    bail!("`str/capitalize`: expected 1 argument1, got {}", exprs.len());
                }
            }),
        },

        BuiltinFunc {
            name: "str/lower",
            callback: Box::new(|state: &State, exprs: &[ExprRef], env: &Env| -> Result<Value, Error> {
                if let [expr] = exprs {
                    let s = state.eval(*expr, env)?;
                    Ok(Value::Lit(Literal::Str(
                        s.as_str(&state.ast.borrow())?.to_lowercase(),
                    )))
                } else {
                    bail!("`str/lower`: expected 1 argument1, got {}", exprs.len());
                }
            }),
        },

        BuiltinFunc {
            name: "add",
            callback: Box::new(|state: &State, exprs: &[ExprRef], env: &Env| -> Result<Value, Error> {
                if let [x, y] = exprs {
                    let x = state.eval(*x, env)?.as_num(&state.ast.borrow())?;
                    let y = state.eval(*y, env)?.as_num(&state.ast.borrow())?;
                    Ok(Value::Lit(Literal::Num(x + y)))
                } else {
                    bail!("`add`: expected 2 arguments, got {}", exprs.len());
                }
            }),
        },

        BuiltinFunc {
            name: "sub",
            callback: Box::new(|state: &State, exprs: &[ExprRef], env: &Env| -> Result<Value, Error> {
                if let [x, y] = exprs {
                    let x = state.eval(*x, env)?.as_num(&state.ast.borrow())?;
                    let y = state.eval(*y, env)?.as_num(&state.ast.borrow())?;
                    Ok(Value::Lit(Literal::Num(x - y)))
                } else {
                    bail!("`sub`: expected 2 arguments, got {}", exprs.len());
                }
            }),
        },

        BuiltinFunc {
            name: "mul",
            callback: Box::new(|state: &State, exprs: &[ExprRef], env: &Env| -> Result<Value, Error> {
                if let [x, y] = exprs {
                    let x = state.eval(*x, env)?.as_num(&state.ast.borrow())?;
                    let y = state.eval(*y, env)?.as_num(&state.ast.borrow())?;
                    Ok(Value::Lit(Literal::Num(x * y)))
                } else {
                    bail!("`mul`: expected 2 arguments, got {}", exprs.len());
                }
            }),
        },

        BuiltinFunc {
            name: "tuple/len",
            callback: Box::new(|state: &State, exprs: &[ExprRef], env: &Env| -> Result<Value, Error> {
                if let [expr] = exprs {
                    let tup = state.eval(*expr, env)?;
                    Ok(Value::Lit(Literal::Num(tup.as_tup(&state.ast.borrow())?.len() as i64)))
                } else {
                    bail!("`tuple/len`: expected 1 argument, got {}", exprs.len())
                }
            }),
        },

        BuiltinFunc {
            name: "tuple/concat",
            callback: Box::new(|state: &State, exprs: &[ExprRef], env: &Env| -> Result<Value, Error> {
                if let [expr] = exprs {
                    let val = state.eval(*expr, env)?;
                    let tup = val.as_tup(&state.ast.borrow())?;
                    let mut contents = Vec::new();
                    for elem in tup {
                        for th in state.hnf(elem)?.as_tup(&state.ast.borrow())? {
                            contents.push(th.clone());
                        }
                    }
                    Ok(Value::Tup(contents))
                } else {
                    bail!("tuple/concat: expected 1 argument, got {}", exprs.len());
                }
            }),
        },

        BuiltinFunc {
            name: "tuple/index",
            callback: Box::new(|state: &State, exprs: &[ExprRef], env: &Env| -> Result<Value, Error> {
                if let [tup, idx] = exprs {
                    let tup = state.eval(*tup, env)?;
                    let idx = state.eval(*idx, env)?;
                    state.hnf(
                        &tup.as_tup(&state.ast.borrow())?
                            [idx.as_num(&state.ast.borrow())? as usize],
                    )
                } else {
                    bail!("`tuple/index`: expected 2 arguments, got {}", exprs.len());
                }
            }),
        },

        BuiltinFunc {
            name: "tuple/replace",
            callback: Box::new(|state: &State, exprs: &[ExprRef], env: &Env| -> Result<Value, Error> {
                if let [tup, idx, new] = exprs {
                    let tup_val = state.eval(*tup, env)?;
                    let tup = tup_val.as_tup(&state.ast.borrow())?;
                    let idx = state.eval(*idx, env)?.as_num(&state.ast.borrow())?;

                    let mut modified = Vec::with_capacity(tup.len());
                    for i in 0..idx {
                        modified.push(tup[i as usize].clone());
                    }
                    modified.push(Thunk::Expr(*new, env.clone()));
                    for i in (idx + 1)..(tup.len() as i64) {
                        modified.push(tup[i as usize].clone());
                    }
                    Ok(Value::Tup(modified))
                } else {
                    bail!("`tuple/replace`: expected 3 arguments, got {}", exprs.len());
                }
            }),
        },

        BuiltinFunc {
            name: "tuple/fold",
            callback: Box::new(|state: &State, exprs: &[ExprRef], env: &Env| -> Result<Value, Error> {
                if let [func, init, tup] = exprs {
                    let func = state.eval(*func, env)?;
                    let tup = state.eval(*tup, env)?;

                    let mut result = Thunk::Expr(*init, env.clone());
                    for t in tup.as_tup(&state.ast.borrow())? {
                        result = Thunk::Value(
                            state.eval_closure(
                                func.as_closure(&state.ast.borrow())?,
                                vec![result, t.clone()],
                            )?);
                    }

                    state.hnf(&result)
                } else {
                    bail!("`tuple/fold`: expected 3 arguments, got {}", exprs.len());
                }
            }),
        },
    ]
}