commit 250e878c0e8327873bccd727797cfeddf7527daa
Author: rowan <rowan@kitsu.cafe>
Date:   Sat Jan 4 15:00:18 2025 -0600

    initial commit

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ea8c4bf
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/target
diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..2f62f9d
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "dolllang"
+version = "0.1.0"
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..7165007
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "dolllang"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..e55614b
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,324 @@
+use core::{fmt, slice};
+use std::error::Error;
+use std::fmt::Debug;
+use std::fs::File;
+use std::io::{BufRead, BufReader, Read};
+use std::num::TryFromIntError;
+use std::result::Result as StdResult;
+use std::{env, fs, io};
+
+enum Input {
+    File(fs::File),
+    Stdin(io::Stdin),
+}
+
+impl Input {
+    fn into_reader(self) -> Box<dyn BufRead> {
+        match self {
+            Input::File(file) => Box::new(BufReader::new(file)),
+            Input::Stdin(stdin) => Box::new(stdin.lock()),
+        }
+    }
+}
+
+impl TryFrom<&str> for Input {
+    type Error = io::Error;
+
+    fn try_from(value: &str) -> StdResult<Self, Self::Error> {
+        match value {
+            "-" => Ok(Self::Stdin(io::stdin())),
+            path => File::open(path).map(Self::File),
+        }
+    }
+}
+
+impl TryFrom<String> for Input {
+    type Error = io::Error;
+
+    fn try_from(value: String) -> StdResult<Self, Self::Error> {
+        value.as_str().try_into()
+    }
+}
+
+#[derive(Debug)]
+struct Tape<T>(T);
+
+impl<T: Read> Tape<T> {
+    pub fn new(value: T) -> Self {
+        Self(value)
+    }
+}
+
+impl<T: Read> Iterator for Tape<T> {
+    type Item = u8;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let mut byte = 0u8;
+        match self.0.read(slice::from_mut(&mut byte)) {
+            Ok(0usize) => None,
+            Ok(_) => Some(byte),
+            Err(_) => None,
+        }
+    }
+}
+
+#[derive(Debug)]
+enum ProgramErrorKind {
+    InvalidSyntax,
+    IllegalMemoryAccess(isize),
+    ConversionError,
+    EndOfFile,
+}
+
+impl fmt::Display for ProgramErrorKind {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            Self::InvalidSyntax => write!(f, "invalid syntax"),
+            Self::EndOfFile => write!(f, "end of file"),
+            Self::IllegalMemoryAccess(loc) => write!(f, "illegal memory access @ {loc}"),
+            Self::ConversionError => todo!(),
+        }
+    }
+}
+
+#[derive(Debug)]
+struct ProgramError {
+    kind: ProgramErrorKind,
+    source: Option<Box<dyn Error>>,
+}
+
+impl ProgramError {
+    pub fn new(kind: ProgramErrorKind, source: impl Into<Box<dyn Error>>) -> Self {
+        Self {
+            kind,
+            source: Some(source.into()),
+        }
+    }
+}
+
+impl From<ProgramErrorKind> for ProgramError {
+    fn from(kind: ProgramErrorKind) -> Self {
+        Self { kind, source: None }
+    }
+}
+
+impl From<TryFromIntError> for ProgramError {
+    fn from(value: TryFromIntError) -> Self {
+        Self::new(ProgramErrorKind::ConversionError, value)
+    }
+}
+
+impl fmt::Display for ProgramError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{} ({:?})", self.kind, self.source)
+    }
+}
+
+impl Error for ProgramError {}
+
+type Result<T> = std::result::Result<T, ProgramError>;
+
+#[derive(PartialEq)]
+enum State {
+    Continue(usize),
+    Halt,
+}
+
+#[derive(Debug)]
+struct Program {
+    memory: Vec<isize>,
+    index: usize,
+}
+
+impl Program {
+    fn word_length(mut word: impl Iterator<Item = u8>) -> Result<isize> {
+        let result = word.try_fold((0isize, true, true), |(count, was_w, pos), byte| {
+            match (byte, was_w, pos) {
+                (b'a', true, true) => Some((count, false, true)),
+                (b'w', false, true) => Some((count + 1, true, true)),
+                (b'!', false, true) => Some((count, false, false)),
+                _ => None,
+            }
+        });
+
+        let sign = match result {
+            Some((_, _, false)) => -1,
+            _ => 1,
+        };
+
+        match result {
+            Some((count, false, _)) => Ok(count * sign),
+            _ => Err(ProgramError::from(ProgramErrorKind::InvalidSyntax)),
+        }
+    }
+
+    fn next_word(program: impl Iterator<Item = u8>) -> Result<isize> {
+        let mut word = program
+            .skip_while(|ch| *ch != b'a' && *ch != b'w' && *ch != b'!')
+            .take_while(|ch| *ch == b'a' || *ch == b'w' || *ch == b'!')
+            .peekable();
+
+        if word.peek().is_none() {
+            Err(ProgramError::from(ProgramErrorKind::EndOfFile))
+        } else {
+            Self::word_length(word)
+        }
+    }
+
+    fn parse(mut program: impl Iterator<Item = u8>) -> Result<Vec<isize>> {
+        let mut memory = Vec::new();
+
+        loop {
+            match Self::next_word(&mut program) {
+                Ok(word) => memory.push(word),
+                Err(ProgramError {
+                    kind: ProgramErrorKind::EndOfFile,
+                    ..
+                }) => break,
+                Err(e) => return Err(e),
+            }
+        }
+
+        Ok(memory)
+    }
+
+    pub fn from_program(program: impl Iterator<Item = u8>) -> Result<Self> {
+        Ok(Self {
+            memory: Self::parse(program)?,
+            index: 0,
+        })
+    }
+
+    fn next_instruction(&self) -> Option<(isize, isize, isize)> {
+        let [a, b, c] = self.memory.get(self.index..=self.index + 2)? else {
+            return None;
+        };
+
+        Some((*a, *b, *c))
+    }
+
+    fn set(&mut self, addr: usize, value: isize) -> Result<()> {
+        if addr > self.memory.len() {
+            Err(ProgramErrorKind::IllegalMemoryAccess(addr as isize).into())
+        } else {
+            self.memory[addr] = value;
+            Ok(())
+        }
+    }
+
+    fn set_isize(&mut self, addr: isize, value: isize) -> Result<()> {
+        if addr < 0 {
+            Err(ProgramErrorKind::IllegalMemoryAccess(addr).into())
+        } else {
+            match usize::try_from(addr) {
+                Ok(addr) => self.set(addr, value),
+                Err(e) => Err(ProgramError::new(ProgramErrorKind::ConversionError, e)),
+            }
+        }
+    }
+
+    fn set_index(&mut self, value: isize) -> Result<()> {
+        if value < 0 {
+            Err(ProgramErrorKind::IllegalMemoryAccess(value).into())
+        } else {
+            match usize::try_from(value) {
+                Ok(value) => {
+                    self.index = value;
+                    Ok(())
+                }
+                Err(e) => Err(ProgramError::new(ProgramErrorKind::ConversionError, e)),
+            }
+        }
+    }
+
+    fn get(&self, n: usize) -> Result<&isize> {
+        match self.memory.get(n) {
+            Some(n) => Ok(n),
+            None => Err(ProgramError::from(ProgramErrorKind::IllegalMemoryAccess(
+                n as isize,
+            ))),
+        }
+    }
+
+    fn get_isize(&self, n: isize) -> Result<&isize> {
+        match usize::try_from(n) {
+            Ok(m) => self.get(m),
+            Err(_) => Err(ProgramError::from(ProgramErrorKind::IllegalMemoryAccess(n))),
+        }
+    }
+
+    fn get_as_usize(&self, n: usize) -> Result<usize> {
+        match self.get(n) {
+            Ok(n) => match usize::try_from(*n) {
+                Ok(m) => Ok(m),
+                Err(e) => Err(e.into()),
+            },
+            Err(e) => Err(e),
+        }
+    }
+
+    fn get_isize_as_usize(&self, n: isize) -> Result<usize> {
+        match usize::try_from(n) {
+            Ok(n) => self.get_as_usize(n),
+            Err(e) => Err(e.into()),
+        }
+    }
+
+    fn step(&mut self) -> Result<State> {
+        if let Some((a, b, c)) = self.next_instruction() {
+            if b == -1 && a > -1 {
+                let ax = self.get_isize_as_usize(a)?.try_into()?;
+                char::from_u32(ax).inspect(|c| print!("{c}"));
+
+                let counter = c.try_into()?;
+                Ok(State::Continue(counter))
+            } else if a > -1 && b > -1 {
+                let ax = self.get_isize(a)?;
+                let bx = self.get_isize(b)?;
+                let next = bx - ax;
+                self.set_isize(b, next)?;
+
+                if next > 0 {
+                    Ok(State::Continue(self.index + 3))
+                } else {
+                    let counter = c.try_into()?;
+                    Ok(State::Continue(counter))
+                }
+            } else {
+                Ok(State::Halt)
+            }
+        } else {
+            Ok(State::Halt)
+        }
+    }
+
+    pub fn execute(&mut self) -> Result<()> {
+        loop {
+            match self.step() {
+                Ok(State::Continue(next)) => {
+                    self.index = next;
+                }
+                Ok(State::Halt) => break,
+                Err(e) => return Err(e),
+            }
+        }
+
+        Ok(())
+    }
+}
+
+fn main() {
+    let args: Vec<String> = env::args().collect();
+    let program: io::Result<Input> = args[1].as_str().try_into();
+
+    let program: &mut dyn Read = match program {
+        Ok(input) => &mut input.into_reader(),
+        Err(_) => &mut args[1].as_bytes(),
+    };
+
+    let mut machine = Program::from_program(Tape::new(program)).expect("failed to load program");
+    machine.execute().expect("<halt>");
+}
+
+#[cfg(test)]
+mod tests {}