use alloc::{format, vec::Vec};
use core::fmt::Debug;
use tracing::debug;
use wasmparser::{
    ExportSectionReader, FunctionBody, FunctionSectionReader, Payload, TypeSectionReader, Validator,
};

use crate::{ParseError, Result};

#[derive(Default)]
pub struct ModuleReader<'a> {
    pub version: Option<u16>,
    pub start_func: Option<u32>,

    pub type_section: Option<TypeSectionReader<'a>>,
    pub function_section: Option<FunctionSectionReader<'a>>,
    pub export_section: Option<ExportSectionReader<'a>>,
    pub code_section: Option<CodeSection<'a>>,

    // pub table_section: Option<TableSectionReader<'a>>,
    // pub memory_section: Option<MemorySectionReader<'a>>,
    // pub global_section: Option<GlobalSectionReader<'a>>,
    // pub element_section: Option<ElementSectionReader<'a>>,
    // pub data_section: Option<DataSectionReader<'a>>,
    // pub import_section: Option<ImportSectionReader<'a>>,
    pub end_reached: bool,
}

impl Debug for ModuleReader<'_> {
    fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
        f.debug_struct("ModuleReader")
            .field("version", &self.version)
            .field("type_section", &self.type_section)
            .field("function_section", &self.function_section)
            .field("code_section", &self.code_section)
            .field("export_section", &self.export_section)
            // .field("table_section", &self.table_section)
            // .field("memory_section", &self.memory_section)
            // .field("global_section", &self.global_section)
            // .field("element_section", &self.element_section)
            // .field("data_section", &self.data_section)
            // .field("import_section", &self.import_section)
            .finish()
    }
}

impl<'a> ModuleReader<'a> {
    pub fn new() -> ModuleReader<'a> {
        Self::default()
    }

    pub fn process_payload(
        &mut self,
        payload: Payload<'a>,
        validator: &mut Validator,
    ) -> Result<()> {
        use wasmparser::Payload::*;

        match payload {
            Version {
                num,
                encoding,
                range,
            } => {
                validator.version(num, encoding, &range)?;
                self.version = Some(num);
                match encoding {
                    wasmparser::Encoding::Module => {}
                    wasmparser::Encoding::Component => {
                        return Err(ParseError::InvalidEncoding(encoding))
                    }
                }
            }
            StartSection { func, range } => {
                debug!("Found start section");
                validator.start_section(func, &range)?;
                self.start_func = Some(func);
            }
            TypeSection(reader) => {
                debug!("Found type section");
                validator.type_section(&reader)?;
                self.type_section = Some(reader);
            }
            FunctionSection(reader) => {
                debug!("Found function section");
                validator.function_section(&reader)?;
                self.function_section = Some(reader);
            }
            TableSection(_reader) => {
                return Err(ParseError::UnsupportedSection("Table section".into()));
                // debug!("Found table section");
                // validator.table_section(&reader)?;
                // self.table_section = Some(reader);
            }
            MemorySection(_reader) => {
                return Err(ParseError::UnsupportedSection("Memory section".into()));
                // debug!("Found memory section");
                // validator.memory_section(&reader)?;
                // self.memory_section = Some(reader);
            }
            GlobalSection(_reader) => {
                return Err(ParseError::UnsupportedSection("Global section".into()));
                // debug!("Found global section");
                // validator.global_section(&reader)?;
                // self.global_section = Some(reader);
            }
            ElementSection(_reader) => {
                return Err(ParseError::UnsupportedSection("Element section".into()));
                // debug!("Found element section");
                // validator.element_section(&reader)?;
                // self.element_section = Some(reader);
            }
            DataSection(_reader) => {
                return Err(ParseError::UnsupportedSection("Data section".into()));
                // debug!("Found data section");
                // validator.data_section(&reader)?;
                // self.data_section = Some(reader);
            }
            CodeSectionStart { count, range, .. } => {
                debug!("Found code section ({} functions)", count);
                if self.code_section.is_some() {
                    return Err(ParseError::DuplicateSection("Code section".into()));
                }

                validator.code_section_start(count, &range)?;
                self.code_section = Some(CodeSection::new());
            }
            CodeSectionEntry(function) => {
                debug!("Found code section entry");
                validator.code_section_entry(&function)?;

                if let Some(code_section) = &mut self.code_section {
                    code_section.functions.push(function);
                } else {
                    return Err(ParseError::EmptySection("Code section".into()));
                }
            }
            ImportSection(_reader) => {
                return Err(ParseError::UnsupportedSection("Import section".into()));

                // debug!("Found import section");
                // validator.import_section(&reader)?;
                // self.import_section = Some(reader);
            }
            ExportSection(reader) => {
                debug!("Found export section");
                validator.export_section(&reader)?;
                self.export_section = Some(reader);
            }
            End(offset) => {
                debug!("Reached end of module");
                if self.end_reached {
                    return Err(ParseError::DuplicateSection("End section".into()));
                }

                validator.end(offset)?;
                self.end_reached = true;
            }
            UnknownSection { .. } | _ => {
                return Err(ParseError::UnsupportedSection(format!("Unknown section")))
            }
        };

        Ok(())
    }
}

/// A WebAssembly code section
/// Can be cloned to read functions multiple times
#[derive(Debug, Clone)]
pub struct CodeSection<'a> {
    pub(crate) functions: Vec<FunctionBody<'a>>,
}

impl<'a> CodeSection<'a> {
    fn new() -> Self {
        Self {
            functions: Vec::new(),
        }
    }
}