/* relish: versatile lisp shell
 * Copyright (C) 2021 Aidan Hahn
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

use crate::segment::{Ctr, Seg, Type};
use crate::sym::{SymTable, Symbol, ValueType, Args};
use crate::error::{Traceback, start_trace};
use std::io::Write;
use std::io;
use std::rc::Rc;

const ECHO_DOCSTRING: &str =
    "traverses any number of arguments. Prints their evaluated values on a new line for each.";
fn echo_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, Traceback> {
    ast.circuit(&mut |arg: &Ctr| match arg {
        Ctr::String(s) => print!("{}", s) == (),
        _ => print!("{}", arg) == (),
    });
    println!();
    Ok(Ctr::None)
}

const CONCAT_DOCSTRING: &str = "Iterates over N args of any type other than SYMBOL.
converts each argument to a string. Combines all strings.
Returns final (combined) string.";
fn concat_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, Traceback> {
    let mut string = String::from("");
    if !ast.circuit(&mut |arg: &Ctr| {
        match arg {
            // should be a thing here
            Ctr::Symbol(_) => return false,
            Ctr::String(s) => string.push_str(&s),
            Ctr::Integer(i) => string.push_str(&i.to_string()),
            Ctr::Float(f) => string.push_str(&f.to_string()),
            Ctr::Bool(b) => string.push_str(&b.to_string()),
            Ctr::Seg(c) => string.push_str(&c.to_string()),
            Ctr::Lambda(l) => string.push_str(&l.to_string()),
            Ctr::None => (),
        }
        true
    }) {
        return Err(start_trace(
            ("concat", "highly suspicious that an input was an unevaluated symbol")
                .into()))
    }
    return Ok(Ctr::String(string));
}

const STRLEN_DOCSTRING: &str = "Takes a single arg of any type.
Arg is converted to a string if not already a string.
Returns string length of arg.";
fn strlen_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, Traceback> {
    match &*ast.car {
        Ctr::Symbol(s) => Ok(Ctr::Integer(s.len() as i128)),
        Ctr::String(s) => Ok(Ctr::Integer(s.len() as i128)),
        Ctr::Integer(i) => Ok(Ctr::Integer(i.to_string().len() as i128)),
        Ctr::Float(f) => Ok(Ctr::Integer(f.to_string().len() as i128)),
        Ctr::Bool(b) => Ok(Ctr::Integer(b.to_string().len() as i128)),
        Ctr::Seg(c) => Ok(Ctr::Integer(c.to_string().len() as i128)),
        Ctr::Lambda(l) => Ok(Ctr::Integer(l.to_string().len() as i128)),
        // highly suspicious case below
        Ctr::None => Ok(Ctr::Integer(0)),
    }
}

const STRCAST_DOCSTRING: &str = "Takes a single arg of any type.
Arg is converted to a string and returned.";
fn strcast_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, Traceback> {
    match &*ast.car {
        Ctr::Symbol(s) => Ok(Ctr::String(s.clone())),
        Ctr::String(_) => Ok(*ast.car.clone()),
        Ctr::Integer(i) => Ok(Ctr::String(i.to_string())),
        Ctr::Float(f) => Ok(Ctr::String(f.to_string())),
        Ctr::Bool(b) => Ok(Ctr::String(b.to_string())),
        Ctr::Seg(c) => Ok(Ctr::String(c.to_string())),
        Ctr::Lambda(l) => Ok(Ctr::String(l.to_string())),
        // highly suspicious case below
        Ctr::None => Ok(Ctr::String(String::new())),
    }
}

const SUBSTR_DOCSTRING: &str =
    "Takes two strings. Returns true if string1 contains at least one instance of string2";
fn substr_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, Traceback> {
    let parent_str: String;
    if let Ctr::String(ref s) = *ast.car {
        parent_str = s.to_string();
    } else {
        return Err(start_trace(
            ("substr", "expected first input to be a string")
                .into()))
    }

    let second_arg_obj: &Ctr;
    let child_str: String;
    if let Ctr::Seg(ref s) = *ast.cdr {
        second_arg_obj = &*s.car;
    } else {
        return Err(start_trace(
            ("substr", "expected two inputs")
                .into()))
    }

    if let Ctr::String(ref s) = &*second_arg_obj {
        child_str = s.clone();
    } else {
        return Err(start_trace(
            ("substr", "expected second input to be a string")
                .into()))
    }

    Ok(Ctr::Bool(parent_str.contains(&child_str)))
}

const SPLIT_DOCSTRING: &str = "Takes two strings. String 1 is a source string and string 2 is a delimiter.
Returns a list of substrings from string 1 that were found delimited by string 2.";
fn split_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, Traceback> {
    let parent_str: String;
    if let Ctr::String(ref s) = *ast.car {
        parent_str = s.to_string();
    } else {
        return Err(start_trace(
            ("split", "expected first input to be a string")
                .into()))
    }

    let second_arg_obj: &Ctr;
    let delim_str: String;
    if let Ctr::Seg(ref s) = *ast.cdr {
        second_arg_obj = &*s.car;
    } else {
        return Err(start_trace(
            ("split", "expected two inputs")
                .into()))
    }

    if let Ctr::String(ref s) = &*second_arg_obj {
        delim_str = s.clone();
    } else {
        return Err(start_trace(
            ("split", "expected second input to be a string")
                .into()))
    }

    let mut ret = Seg::new();
    for substr in parent_str.split(&delim_str) {
        ret.append(Box::new(Ctr::String(substr.to_string())));
    }

    Ok(Ctr::Seg(ret))
}

const INPUT_DOCSTRING: &str = "Takes one argument (string) and prints it.
Then prompts for user input.
User input is returned as a string";
fn input_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, Traceback> {
    if let Ctr::String(ref s) = *ast.car {
        print!("{}", s);
        let _= io::stdout().flush();
        let mut input = String::new();
        io::stdin().read_line(&mut input).expect("couldnt read user input");
        Ok(Ctr::String(input.trim().to_string()))
    } else {
        return Err(start_trace(
            ("input", "expected a string input to prompt user with")
                .into()))
    }
}

pub fn add_string_lib(syms: &mut SymTable) {
    syms.insert(
        "echo".to_string(),
        Symbol {
            name: String::from("echo"),
            args: Args::Infinite,
            conditional_branches: false,
            docs: ECHO_DOCSTRING.to_string(),
            value: ValueType::Internal(Rc::new(echo_callback)),
            ..Default::default()
        },
    );

    syms.insert(
        "concat".to_string(),
        Symbol {
            name: String::from("concat"),
            args: Args::Infinite,
            conditional_branches: false,
            docs: CONCAT_DOCSTRING.to_string(),
            value: ValueType::Internal(Rc::new(concat_callback)),
            ..Default::default()
        },
    );

    syms.insert(
        "substr?".to_string(),
        Symbol {
            name: String::from("substr?"),
            args: Args::Strict(vec![Type::String, Type::String]),
            conditional_branches: false,
            docs: SUBSTR_DOCSTRING.to_string(),
            value: ValueType::Internal(Rc::new(substr_callback)),
            ..Default::default()
        },
    );

    syms.insert(
        "split".to_string(),
        Symbol {
            name: String::from("split"),
            args: Args::Strict(vec![Type::String, Type::String]),
            conditional_branches: false,
            docs: SPLIT_DOCSTRING.to_string(),
            value: ValueType::Internal(Rc::new(split_callback)),
            ..Default::default()
        },
    );

    syms.insert(
        "strlen".to_string(),
        Symbol {
            name: String::from("strlen"),
            args: Args::Lazy(1),
            conditional_branches: false,
            docs: STRLEN_DOCSTRING.to_string(),
            value: ValueType::Internal(Rc::new(strlen_callback)),
            ..Default::default()
        },
    );

    syms.insert(
        "string".to_string(),
        Symbol {
            name: String::from("string"),
            args: Args::Lazy(1),
            conditional_branches: false,
            docs: STRCAST_DOCSTRING.to_string(),
            value: ValueType::Internal(Rc::new(strcast_callback)),
            ..Default::default()
        },
    );

    syms.insert(
        "input".to_string(),
        Symbol {
            name: String::from("input"),
            args: Args::Strict(vec![Type::String]),
            conditional_branches: false,
            docs: INPUT_DOCSTRING.to_string(),
            value: ValueType::Internal(Rc::new(input_callback)),
            ..Default::default()
        }
    );
}