use std::fmt::{self, Debug, Display, Formatter};

use serde::{Deserialize, Serialize};

use crate::{AnnotatedError, Identifier, Instruction, Span, Value};

#[derive(Clone)]
pub struct Chunk {
    code: Vec<(Instruction, Span)>,
    constants: Vec<Option<Value>>,
    identifiers: Vec<Local>,
    scope_depth: usize,
}

impl Chunk {
    pub fn new() -> Self {
        Self {
            code: Vec::new(),
            constants: Vec::new(),
            identifiers: Vec::new(),
            scope_depth: 0,
        }
    }

    pub fn with_data(
        code: Vec<(Instruction, Span)>,
        constants: Vec<Value>,
        identifiers: Vec<Local>,
    ) -> Self {
        Self {
            code,
            constants: constants.into_iter().map(Some).collect(),
            identifiers,
            scope_depth: 0,
        }
    }

    pub fn len(&self) -> usize {
        self.code.len()
    }

    pub fn is_empty(&self) -> bool {
        self.code.is_empty()
    }

    pub fn scope_depth(&self) -> usize {
        self.scope_depth
    }

    pub fn get_code(
        &self,
        offset: usize,
        position: Span,
    ) -> Result<&(Instruction, Span), ChunkError> {
        self.code
            .get(offset)
            .ok_or(ChunkError::CodeIndexOfBounds { offset, position })
    }

    pub fn push_code(&mut self, instruction: Instruction, position: Span) {
        self.code.push((instruction, position));
    }

    pub fn get_constant(&self, index: u16, position: Span) -> Result<&Value, ChunkError> {
        self.constants
            .get(index as usize)
            .ok_or(ChunkError::ConstantIndexOutOfBounds { index, position })
            .and_then(|value| {
                value
                    .as_ref()
                    .ok_or(ChunkError::ConstantAlreadyUsed { index, position })
            })
    }

    pub fn use_constant(&mut self, index: u16, position: Span) -> Result<Value, ChunkError> {
        self.constants
            .get_mut(index as usize)
            .ok_or_else(|| ChunkError::ConstantIndexOutOfBounds { index, position })?
            .take()
            .ok_or(ChunkError::ConstantAlreadyUsed { index, position })
    }

    pub fn push_constant(&mut self, value: Value, position: Span) -> Result<u16, ChunkError> {
        let starting_length = self.constants.len();

        if starting_length + 1 > (u8::MAX as usize) {
            Err(ChunkError::ConstantOverflow { position })
        } else {
            self.constants.push(Some(value));

            Ok(starting_length as u16)
        }
    }

    pub fn contains_identifier(&self, identifier: &Identifier) -> bool {
        self.identifiers
            .iter()
            .any(|local| &local.identifier == identifier)
    }

    pub fn get_local(&self, index: u16, position: Span) -> Result<&Local, ChunkError> {
        self.identifiers
            .get(index as usize)
            .ok_or(ChunkError::IdentifierIndexOutOfBounds { index, position })
    }

    pub fn get_identifier(&self, index: u8) -> Option<&Identifier> {
        if let Some(local) = self.identifiers.get(index as usize) {
            Some(&local.identifier)
        } else {
            None
        }
    }

    pub fn get_identifier_index(
        &self,
        identifier: &Identifier,
        position: Span,
    ) -> Result<u16, ChunkError> {
        self.identifiers
            .iter()
            .rev()
            .enumerate()
            .find_map(|(index, local)| {
                if &local.identifier == identifier {
                    Some(index as u16)
                } else {
                    None
                }
            })
            .ok_or(ChunkError::IdentifierNotFound {
                identifier: identifier.clone(),
                position,
            })
    }

    pub fn declare_variable(
        &mut self,
        identifier: Identifier,
        position: Span,
    ) -> Result<u16, ChunkError> {
        let starting_length = self.identifiers.len();

        if starting_length + 1 > (u8::MAX as usize) {
            Err(ChunkError::IdentifierOverflow { position })
        } else {
            self.identifiers.push(Local {
                identifier,
                depth: self.scope_depth,
            });

            Ok(starting_length as u16)
        }
    }

    pub fn begin_scope(&mut self) {
        self.scope_depth += 1;
    }

    pub fn end_scope(&mut self) {
        self.scope_depth -= 1;
    }

    pub fn clear(&mut self) {
        self.code.clear();
        self.constants.clear();
        self.identifiers.clear();
    }

    pub fn identifiers(&self) -> &[Local] {
        &self.identifiers
    }

    pub fn pop_identifier(&mut self) -> Option<Local> {
        self.identifiers.pop()
    }

    pub fn disassemble(&self, name: &str) -> String {
        let mut output = String::new();

        let name_length = name.len();
        let buffer_length = 34_usize.saturating_sub(name_length + 2);
        let name_buffer = " ".repeat(buffer_length / 2);
        let name_line = format!("{name_buffer}{name}{name_buffer}\n");
        let name_underline = format!("{name_buffer}{}{name_buffer}\n", "-".repeat(name_length));

        output.push_str(&name_line);
        output.push_str(&name_underline);
        output.push_str("\n              Code              \n");
        output.push_str("------ -------- ------------\n");
        output.push_str("OFFSET POSITION INSTRUCTION\n");
        output.push_str("------ -------- ------------\n");

        for (offset, (instruction, position)) in self.code.iter().enumerate() {
            let display = format!(
                "{offset:04}   {position}   {}\n",
                instruction.disassemble(self)
            );

            output.push_str(&display);
        }

        output.push_str("\n   Constants\n");
        output.push_str("----- ---- -----\n");
        output.push_str("INDEX KIND VALUE\n");
        output.push_str("----- ---- -----\n");

        for (index, value_option) in self.constants.iter().enumerate() {
            let value_kind_display = match value_option {
                Some(Value::Raw(_)) => "RAW ",
                Some(Value::Reference(_)) => "REF ",
                Some(Value::Mutable(_)) => "MUT ",
                None => "EMPTY",
            };
            let value_display = value_option
                .as_ref()
                .map(|value| value.to_string())
                .unwrap_or_else(|| "EMPTY".to_string());
            let display = format!("{index:3}   {value_kind_display} {value_display}\n",);

            output.push_str(&display);
        }

        output.push_str("\n      Identifiers\n");
        output.push_str("----- ---------- -----\n");
        output.push_str("INDEX NAME       DEPTH\n");
        output.push_str("----- ---------- -----\n");

        for (index, Local { identifier, depth }) in self.identifiers.iter().enumerate() {
            let display = format!("{index:3}   {:10} {depth}\n", identifier.as_str());
            output.push_str(&display);
        }

        output
    }
}

impl Default for Chunk {
    fn default() -> Self {
        Self::new()
    }
}

impl Display for Chunk {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        write!(f, "{}", self.disassemble("Chunk Disassembly"))
    }
}

impl Debug for Chunk {
    fn fmt(&self, f: &mut Formatter) -> fmt::Result {
        write!(f, "{}", self.disassemble("Chunk Disassembly"))
    }
}

impl Eq for Chunk {}

impl PartialEq for Chunk {
    fn eq(&self, other: &Self) -> bool {
        self.code == other.code
            && self.constants == other.constants
            && self.identifiers == other.identifiers
    }
}

#[derive(Debug, Clone, Eq, PartialEq, Serialize, Deserialize)]
pub struct Local {
    pub identifier: Identifier,
    pub depth: usize,
}

#[derive(Debug, Clone, PartialEq)]
pub enum ChunkError {
    CodeIndexOfBounds {
        offset: usize,
        position: Span,
    },
    ConstantAlreadyUsed {
        index: u16,
        position: Span,
    },
    ConstantOverflow {
        position: Span,
    },
    ConstantIndexOutOfBounds {
        index: u16,
        position: Span,
    },
    IdentifierIndexOutOfBounds {
        index: u16,
        position: Span,
    },
    IdentifierOverflow {
        position: Span,
    },
    IdentifierNotFound {
        identifier: Identifier,
        position: Span,
    },
}

impl AnnotatedError for ChunkError {
    fn title() -> &'static str {
        "Chunk Error"
    }

    fn description(&self) -> &'static str {
        match self {
            ChunkError::CodeIndexOfBounds { .. } => "Code index out of bounds",
            ChunkError::ConstantAlreadyUsed { .. } => "Constant already used",
            ChunkError::ConstantOverflow { .. } => "Constant overflow",
            ChunkError::ConstantIndexOutOfBounds { .. } => "Constant index out of bounds",
            ChunkError::IdentifierIndexOutOfBounds { .. } => "Identifier index out of bounds",
            ChunkError::IdentifierOverflow { .. } => "Identifier overflow",
            ChunkError::IdentifierNotFound { .. } => "Identifier not found",
        }
    }

    fn details(&self) -> Option<String> {
        match self {
            ChunkError::CodeIndexOfBounds { offset, .. } => Some(format!("Code index: {}", offset)),
            ChunkError::ConstantAlreadyUsed { index, .. } => {
                Some(format!("Constant index: {}", index))
            }
            ChunkError::ConstantIndexOutOfBounds { index, .. } => {
                Some(format!("Constant index: {}", index))
            }
            ChunkError::IdentifierIndexOutOfBounds { index, .. } => {
                Some(format!("Identifier index: {}", index))
            }
            ChunkError::IdentifierNotFound { identifier, .. } => {
                Some(format!("Identifier: {}", identifier))
            }
            _ => None,
        }
    }

    fn position(&self) -> Span {
        match self {
            ChunkError::CodeIndexOfBounds { position, .. } => *position,
            ChunkError::ConstantAlreadyUsed { position, .. } => *position,
            ChunkError::ConstantIndexOutOfBounds { position, .. } => *position,
            ChunkError::IdentifierNotFound { position, .. } => *position,
            _ => todo!(),
        }
    }
}