use std::{
    collections::HashMap,
    io::BufRead,
    io::{self, Write},
};

use crate::{
    operation::RegisterOperation,
    parser::{parse, Instruction, Line, RegisterContents, ResultValue, Value},
    runtime_state::Register,
};

struct Debugger {
    registers: HashMap<char, Register>,
    lines: Vec<(usize, Line)>,
    found_labels: HashMap<u32, usize>,
}

fn ellipsis(source: String, len: usize) -> String {
    source
        .get(..len)
        .map(|sub| format!("{sub}..."))
        .unwrap_or(source.to_string())
}

impl Debugger {
    fn get_register(&mut self, name: char) -> Result<&mut Register, String> {
        self.registers
            .get_mut(&name)
            .ok_or(format!("Register {name} not defined"))
    }

    fn resolve(&self, value: Value) -> Result<u32, String> {
        match value {
            Value::Register(name) => self
                .registers
                .get(&name)
                .map(|reg| reg.get())
                .ok_or(format!("Register {name} not defined")),
            Value::Number(value) => Ok(value.into()),
        }
    }

    pub fn debug(mut self) -> Result<(), String> {
        let mut pc = 0;
        let mut target: Option<usize> = None;
        let mut ops_since_target_set = 0;
        let mut sorted_register_names = self
            .registers
            .iter()
            .map(|(name, _)| name.clone())
            .collect::<Vec<char>>();
        sorted_register_names.sort();

        loop {
            let mut jumped = false;
            let (line_num, line) = match self.lines.get(pc).cloned() {
                Some(val) => val,
                None => return Ok(()),
            };
            println!("{line_num}: {line}");
            match &line.instruction {
                Instruction::Register(name, op, value) => {
                    let num = self.resolve(value.clone())?;
                    let register = self.get_register(name.clone())?;
                    match op {
                        RegisterOperation::Right => register.right(num),
                        RegisterOperation::Left => register.left(num),
                        RegisterOperation::Add => register.add(num.try_into().unwrap()),
                        RegisterOperation::Subtract => register.sub(num),
                    }
                }
                Instruction::Result(value) => match value {
                    ResultValue::All => println!("="),
                    ResultValue::Register(reg) => println!("= {}", self.get_register(*reg)?.get()),
                    ResultValue::Value(val) => println!("= {}", self.resolve(*val)?),
                },
                Instruction::Jump(reg, to) => {
                    if reg
                        .map(|r| -> Result<bool, String> { Ok(self.get_register(r)?.get() > 0) })
                        .unwrap_or(Ok(true))?
                    {
                        pc = self
                            .found_labels
                            .get(to)
                            .ok_or("Label {to} not defined")?
                            .to_owned();
                        jumped = true;
                    }
                }
                Instruction::Take(to, from) => {
                    let val = self.get_register(*from)?.remove() + self.get_register(*to)?.get();
                    self.get_register(*to)?.insert(val);
                }
            }
            for name in sorted_register_names.iter() {
                println!(
                    "{name}:{}",
                    ellipsis(format!("{}", self.registers.get(name).unwrap()), 80)
                )
            }
            if let Some(to) = target {
                if line_num == to {
                    target = None
                }
            }
            if ops_since_target_set > 1000 {
                target = None
            }
            io::stdout().flush().unwrap();
            if target.is_none() {
                target = io::stdin()
                    .lock()
                    .lines()
                    .next()
                    .map(|s| s.unwrap().parse().ok())
                    .unwrap_or_default();
                ops_since_target_set = 0
            } else {
                println!("");
                ops_since_target_set += 1
            }
            if !jumped {
                pc += 1;
            }
        }
    }

    fn new(source: &str) -> Result<Self, String> {
        let (lines, register_definitions) =
            parse(source).map_err(|e| format!("{}:{}", e.line, e.message))?;
        let registers = register_definitions
            .into_iter()
            .map(|(_, def)| {
                (
                    def.name,
                    Register {
                        content: match def.contents {
                            RegisterContents::Size(size) => {
                                let mut content = Vec::new();
                                content.resize(size.into(), 0);
                                content
                            }
                            RegisterContents::Values(values) => {
                                values.into_iter().map(|i| i as u32).collect()
                            }
                        },
                        cursor: 0,
                    },
                )
            })
            .collect::<HashMap<char, Register>>();
        let found_labels = lines
            .iter()
            .enumerate()
            .filter_map(|(num, (line_num, line))| line.label.map(|name| (name, num, line_num)))
            .try_fold(
                HashMap::<u32, usize>::new(),
                |mut m, (name, offset, line_num)| {
                    if m.get(&name).is_some() {
                        Err(format!("{line_num}: Label {} already defined", name))
                    } else {
                        m.insert(name.try_into().unwrap(), offset);
                        Ok(m)
                    }
                },
            )?;

        Ok(Self {
            registers,
            lines,
            found_labels,
        })
    }
}

pub fn debug(source: &str) -> Result<(), String> {
    Debugger::new(source)?.debug()
}