use crate::log::debug;
use crate::{ParseError, ParserOptions, Result, conversion, optimize};
use alloc::sync::Arc;
use alloc::{format, string::ToString, vec::Vec};
use core::marker::PhantomData;
use core::ops::Range;
use tinywasm_types::*;
use wasmparser::{FuncValidatorAllocations, Payload, Validator};

pub(crate) struct FunctionCode {
    pub instructions: Vec<Instruction>,
    pub data: WasmFunctionData,
    pub locals: ValueCounts,
    pub uses_local_memory: bool,
}

pub(crate) fn imported_func_count(imports: &[Import]) -> usize {
    imports.iter().filter(|i| matches!(&i.kind, ImportKind::Function(_))).count()
}

pub(crate) fn imported_memory_count(imports: &[Import]) -> u32 {
    imports.iter().filter(|i| matches!(&i.kind, ImportKind::Memory(_))).count() as u32
}

pub(crate) fn optimize_function_code(
    mut code: FunctionCode,
    options: &ParserOptions,
    function_results: ValueCounts,
    self_func_addr: u32,
    imported_memory_count: u32,
) -> FunctionCode {
    let optimized = optimize::optimize_instructions(
        code.instructions,
        &mut code.data,
        options,
        function_results,
        self_func_addr,
        imported_memory_count,
    );

    code.instructions = optimized.instructions;
    code.uses_local_memory = optimized.uses_local_memory;
    code
}

#[derive(Default)]
pub(crate) struct ModuleReader<'a> {
    func_validator_allocations: Option<FuncValidatorAllocations>,
    has_code_section: bool,
    marker: PhantomData<&'a [u8]>,

    pub(crate) version: Option<u16>,
    pub(crate) start_func: Option<u32>,
    pub(crate) func_types: Vec<Arc<FuncType>>,
    pub(crate) code_type_addrs: Vec<u32>,
    pub(crate) exports: Vec<Export>,
    pub(crate) code: Vec<FunctionCode>,
    pub(crate) globals: Vec<Global>,
    pub(crate) table_types: Vec<TableType>,
    pub(crate) memory_types: Vec<MemoryType>,
    pub(crate) imports: Vec<Import>,
    pub(crate) data: Vec<Data>,
    pub(crate) elements: Vec<Element>,
    pub(crate) end_reached: bool,

    #[cfg(parallel_parser)]
    pending_functions: Option<Vec<crate::parallel::PendingFunction<'a>>>,
}

impl<'a> ModuleReader<'a> {
    fn function_results(&self, ordinal: usize) -> ValueCounts {
        let ty_idx = self.code_type_addrs[ordinal];
        let ty = self.func_types.get(ty_idx as usize).expect("No func type for func, this is a bug");
        ValueCounts::from_iter(ty.results())
    }

    pub(crate) fn process_payload(&mut self, payload: Payload<'_>, validator: &mut Validator) -> Result<()> {
        match payload {
            Payload::Version { num, encoding, range } => {
                validator.version(num, encoding, &range)?;
                self.version = Some(num);
                if let wasmparser::Encoding::Component = encoding {
                    return Err(ParseError::InvalidEncoding(encoding));
                }
            }
            Payload::StartSection { func, range } => {
                if self.start_func.is_some() {
                    return Err(ParseError::DuplicateSection("Start section".into()));
                }

                debug!("Found start section");
                validator.start_section(func, &range)?;
                self.start_func = Some(func);
            }
            Payload::TypeSection(reader) => {
                if !self.func_types.is_empty() {
                    return Err(ParseError::DuplicateSection("Type section".into()));
                }

                debug!("Found type section");
                validator.type_section(&reader)?;
                self.func_types =
                    reader.into_iter().map(|t| conversion::convert_module_type(t?)).collect::<Result<Vec<_>>>()?;
            }
            Payload::GlobalSection(reader) => {
                if !self.globals.is_empty() {
                    return Err(ParseError::DuplicateSection("Global section".into()));
                }

                debug!("Found global section");
                validator.global_section(&reader)?;
                self.globals = conversion::convert_module_globals(reader)?;
            }
            Payload::TableSection(reader) => {
                if !self.table_types.is_empty() {
                    return Err(ParseError::DuplicateSection("Table section".into()));
                }

                debug!("Found table section");
                validator.table_section(&reader)?;
                self.table_types = conversion::convert_module_tables(reader)?;
            }
            Payload::MemorySection(reader) => {
                if !self.memory_types.is_empty() {
                    return Err(ParseError::DuplicateSection("Memory section".into()));
                }

                debug!("Found memory section");
                validator.memory_section(&reader)?;
                self.memory_types = conversion::convert_module_memories(reader)?;
            }
            Payload::ElementSection(reader) => {
                debug!("Found element section");
                validator.element_section(&reader)?;
                self.elements = conversion::convert_module_elements(reader)?;
            }
            Payload::DataSection(reader) => {
                if !self.data.is_empty() {
                    return Err(ParseError::DuplicateSection("Data section".into()));
                }

                debug!("Found data section");
                validator.data_section(&reader)?;
                self.data = conversion::convert_module_data_sections(reader)?;
            }
            Payload::DataCountSection { count, range } => {
                debug!("Found data count section");
                if !self.data.is_empty() {
                    return Err(ParseError::DuplicateSection("Data count section".into()));
                }
                validator.data_count_section(count, &range)?;
            }
            Payload::FunctionSection(reader) => {
                if !self.code_type_addrs.is_empty() {
                    return Err(ParseError::DuplicateSection("Function section".into()));
                }

                debug!("Found function section");
                validator.function_section(&reader)?;
                self.code_type_addrs = reader.into_iter().map(|f| Ok(f?)).collect::<Result<Vec<_>>>()?;
            }
            Payload::ImportSection(reader) => {
                if !self.imports.is_empty() {
                    return Err(ParseError::DuplicateSection("Import section".into()));
                }

                debug!("Found import section");
                validator.import_section(&reader)?;
                self.imports = conversion::convert_module_imports(reader.into_imports())?;
            }
            Payload::ExportSection(reader) => {
                if !self.exports.is_empty() {
                    return Err(ParseError::DuplicateSection("Export section".into()));
                }

                debug!("Found export section");
                validator.export_section(&reader)?;
                self.exports =
                    reader.into_iter().map(|e| conversion::convert_module_export(e?)).collect::<Result<Vec<_>>>()?;
            }
            Payload::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;
            }
            Payload::CustomSection(_reader) => {
                debug!("Found custom section");
                debug!("Skipping custom section: {:?}", _reader.name());
            }
            Payload::CodeSectionStart { .. } | Payload::CodeSectionEntry(_) => {
                return Err(ParseError::Other("code section payload handled separately".into()));
            }
            Payload::UnknownSection { .. } => return Err(ParseError::UnsupportedSection("Unknown section".into())),
            section => return Err(ParseError::UnsupportedSection(format!("Unsupported section: {section:?}"))),
        }

        Ok(())
    }

    pub(crate) fn begin_code_section(
        &mut self,
        count: u32,
        range: Range<usize>,
        size: u32,
        validator: &mut Validator,
        options: &ParserOptions,
    ) -> Result<bool> {
        debug!("Found code section ({count} functions)");
        if self.has_code_section {
            return Err(ParseError::DuplicateSection("Code section".into()));
        }

        self.has_code_section = true;
        self.code.reserve(count as usize);
        validator.code_section_start(&range)?;

        #[cfg(parallel_parser)]
        {
            let defer = crate::parallel::should_use_parallel(options, count as usize, size as usize);
            if defer {
                debug!("Queuing {count} functions from {size} byte code section");
                self.pending_functions = Some(Vec::with_capacity(count as usize));
            }
            Ok(defer)
        }

        #[cfg(not(parallel_parser))]
        {
            let _ = (size, options);
            Ok(false)
        }
    }

    pub(crate) fn process_inline_code_section_entry(
        &mut self,
        function: wasmparser::FunctionBody<'_>,
        validator: &mut Validator,
        options: &ParserOptions,
    ) -> Result<()> {
        debug!("Found code section entry");
        let ordinal = self.code.len();
        let func_to_validate = validator.code_section_entry(&function)?;
        let func_validator =
            func_to_validate.into_validator(self.func_validator_allocations.take().unwrap_or_default());
        let (code, allocations) = conversion::convert_module_code(function, func_validator)?;
        let code = optimize_function_code(
            code,
            options,
            self.function_results(ordinal),
            (imported_func_count(&self.imports) + ordinal) as u32,
            imported_memory_count(&self.imports),
        );
        self.code.push(code);
        self.func_validator_allocations = Some(allocations);
        Ok(())
    }

    pub(crate) fn process_borrowed_code_section_entry(
        &mut self,
        function: wasmparser::FunctionBody<'a>,
        validator: &mut Validator,
        options: &ParserOptions,
    ) -> Result<()> {
        debug!("Found code section entry");

        #[cfg(parallel_parser)]
        if let Some(pending) = self.pending_functions.as_mut() {
            let func_to_validate = validator.code_section_entry(&function)?;
            let ordinal = self.code.len() + pending.len();
            let ty_idx = self.code_type_addrs[ordinal];
            pending.push(crate::parallel::PendingFunction {
                ordinal,
                ty_idx,
                func_to_validate,
                body: crate::parallel::FunctionBodyInput::Borrowed(function),
            });
            return Ok(());
        }

        self.process_inline_code_section_entry(function, validator, options)
    }

    #[cfg(parallel_parser)]
    pub(crate) fn queue_owned_code_section(
        &mut self,
        count: u32,
        body_offset: usize,
        section_bytes: Arc<[u8]>,
        validator: &mut Validator,
    ) -> Result<()> {
        let code_len = self.code.len();
        let pending = self
            .pending_functions
            .as_mut()
            .ok_or_else(|| ParseError::Other("owned code section queued without pending storage".into()))?;

        let mut reader = wasmparser::BinaryReader::new(&section_bytes, body_offset);
        for _ in 0..count {
            let body_reader = reader.read_reader()?;
            let body_range = body_reader.range();
            let function = wasmparser::FunctionBody::new(body_reader);
            let func_to_validate = validator.code_section_entry(&function)?;
            let ordinal = code_len + pending.len();
            let ty_idx = self.code_type_addrs[ordinal];
            pending.push(crate::parallel::PendingFunction {
                ordinal,
                ty_idx,
                func_to_validate,
                body: crate::parallel::FunctionBodyInput::Owned(crate::parallel::OwnedFunctionBody {
                    section_bytes: section_bytes.clone(),
                    body_range: (body_range.start - body_offset)..(body_range.end - body_offset),
                    body_offset: body_range.start,
                }),
            });
        }

        if reader.bytes_remaining() != 0 {
            return Err(ParseError::ParseError {
                message: "trailing bytes at end of section".into(),
                offset: reader.original_position(),
            });
        }

        Ok(())
    }

    #[cfg(parallel_parser)]
    pub(crate) fn process_pending_functions(&mut self, options: &ParserOptions) -> Result<()> {
        let Some(pending) = self.pending_functions.take().filter(|pending| !pending.is_empty()) else {
            return Ok(());
        };

        self.code.extend(crate::parallel::process_pending(
            pending,
            options,
            &self.func_types,
            imported_func_count(&self.imports),
            imported_memory_count(&self.imports),
        )?);
        Ok(())
    }

    #[cfg(not(parallel_parser))]
    pub(crate) fn process_pending_functions(&mut self, _options: &ParserOptions) -> Result<()> {
        Ok(())
    }

    pub(crate) fn into_module(self, options: &ParserOptions) -> Result<Module> {
        if !self.end_reached {
            return Err(ParseError::EndNotReached);
        }

        if self.code_type_addrs.len() != self.code.len() {
            return Err(ParseError::Other("Code and code type address count mismatch".to_string()));
        }

        let import_mem_count = imported_memory_count(&self.imports);
        let has_local_mem_export =
            self.exports.iter().any(|export| export.kind == ExternalKind::Memory && export.index >= import_mem_count);
        let has_active_data_segment_on_local_memory = self.data.iter().any(|data| match &data.kind {
            DataKind::Active { mem, .. } => *mem >= import_mem_count,
            DataKind::Passive => false,
        });
        let optimize_local_memory_allocation = options.optimize_local_memory_allocation();
        let mut local_memory_allocation = if self.memory_types.is_empty() {
            LocalMemoryAllocation::Skip
        } else if !optimize_local_memory_allocation || has_active_data_segment_on_local_memory {
            LocalMemoryAllocation::Eager
        } else if has_local_mem_export {
            LocalMemoryAllocation::Lazy
        } else {
            LocalMemoryAllocation::Skip
        };

        let mut funcs = Vec::with_capacity(self.code.len());
        let mut func_type_idxs = self
            .imports
            .iter()
            .filter_map(|import| match import.kind {
                ImportKind::Function(type_idx) => Some(type_idx),
                _ => None,
            })
            .collect::<Vec<_>>();
        func_type_idxs.extend(self.code_type_addrs.iter().copied());

        for (code, ty_idx) in self.code.into_iter().zip(self.code_type_addrs) {
            let ty = self.func_types.get(ty_idx as usize).expect("No func type for func, this is a bug").clone();
            let params = ValueCounts::from_iter(ty.params());
            let results = ValueCounts::from_iter(ty.results());
            if code.uses_local_memory {
                local_memory_allocation = LocalMemoryAllocation::Eager;
            }

            funcs.push(
                WasmFunction {
                    instructions: code.instructions.into(),
                    data: code.data,
                    locals: code.locals,
                    params,
                    results,
                    ty,
                }
                .into(),
            );
        }

        Ok(ModuleInner {
            funcs: funcs.into(),
            func_types: self.func_types.into(),
            func_type_idxs: func_type_idxs.into(),
            globals: self.globals.into(),
            table_types: self.table_types.into(),
            imports: self.imports.into(),
            start_func: self.start_func,
            data: self.data.into(),
            exports: self.exports.into(),
            elements: self.elements.into(),
            memory_types: self.memory_types.into(),
            local_memory_allocation,
        }
        .into())
    }
}