use crate::{
    instance::{Import, ImportResolver},
    memory::LinearMemory,
    module::{ImportName, Module},
    table::{TableBacking, TableElements},
    types::{Initializer, MapIndex, Value},
    vm,
};

#[derive(Debug)]
pub struct LocalBacking {
    pub memories: Box<[LinearMemory]>,
    pub tables: Box<[TableBacking]>,

    pub vm_memories: Box<[vm::LocalMemory]>,
    pub vm_tables: Box<[vm::LocalTable]>,
    pub vm_globals: Box<[vm::LocalGlobal]>,
    pub vm_signatures: Box<[vm::SigId]>,
}

impl LocalBacking {
    pub fn new(module: &Module, imports: &ImportBacking) -> Self {
        let mut memories = Self::generate_memories(module);
        let mut tables = Self::generate_tables(module);
        let globals = Self::generate_globals(module);

        let vm_memories = Self::finalize_memories(module, &mut memories[..]);
        let vm_tables = Self::finalize_tables(module, imports, &mut tables[..]);
        let vm_globals = Self::finalize_globals(module, imports, globals);
        let vm_signatures = module.sig_registry.into_vm_sigid();

        Self {
            memories,
            tables,

            vm_memories,
            vm_tables,
            vm_globals,
            vm_signatures,
        }
    }

    fn generate_memories(module: &Module) -> Box<[LinearMemory]> {
        let mut memories = Vec::with_capacity(module.memories.len());

        for (_, mem) in &module.memories {
            // If we use emscripten, we set a fixed initial and maximum
            debug!("Instance - init memory ({}, {:?})", mem.min, mem.max);
            // let memory = if options.abi == InstanceABI::Emscripten {
            //     // We use MAX_PAGES, so at the end the result is:
            //     // (initial * LinearMemory::PAGE_SIZE) == LinearMemory::DEFAULT_HEAP_SIZE
            //     // However, it should be: (initial * LinearMemory::PAGE_SIZE) == 16777216
            //     LinearMemory::new(LinearMemory::MAX_PAGES, None)
            // } else {
            //     LinearMemory::new(memory.minimum, memory.maximum.map(|m| m as u32))
            // };
            let memory = LinearMemory::new(mem);
            memories.push(memory);
        }

        memories.into_boxed_slice()
    }

    fn finalize_memories(module: &Module, memories: &mut [LinearMemory]) -> Box<[vm::LocalMemory]> {
        for init in &module.data_initializers {
            assert!(init.base.is_none(), "global base not supported yet");
            assert!(
                init.offset + init.data.len() <= memories[init.memory_index.index()].current_size()
            );
            let offset = init.offset;
            let mem: &mut LinearMemory = &mut memories[init.memory_index.index()];
            // let end_of_init = offset + init.data.len();
            // if end_of_init > mem.current_size() {
            //     let grow_pages = (end_of_init / LinearMemory::PAGE_SIZE as usize) + 1;
            //     mem.grow(grow_pages as u32)
            //         .expect("failed to grow memory for data initializers");
            // }
            let to_init = &mut mem[offset..offset + init.data.len()];
            to_init.copy_from_slice(&init.data);
        }

        memories
            .iter_mut()
            .map(|mem| mem.into_vm_memory())
            .collect::<Vec<_>>()
            .into_boxed_slice()
    }

    fn generate_tables(module: &Module) -> Box<[TableBacking]> {
        let mut tables = Vec::with_capacity(module.tables.len());

        for (_, table) in &module.tables {
            let table_backing = TableBacking::new(table);
            tables.push(table_backing);
        }

        tables.into_boxed_slice()
    }

    fn finalize_tables(
        module: &Module,
        imports: &ImportBacking,
        tables: &mut [TableBacking],
    ) -> Box<[vm::LocalTable]> {
        for init in &module.table_initializers {
            assert!(init.base.is_none(), "global base not supported yet");
            let table = &mut tables[init.table_index.index()];
            match table.elements {
                TableElements::Anyfunc(ref mut elements) => {
                    for (i, &func_index) in init.elements.iter().enumerate() {
                        let sig_index = module.func_assoc[func_index];
                        let vm_sig_id = vm::SigId(sig_index.index() as u32);

                        let func_data = if module.is_imported_function(func_index) {
                            imports.functions[func_index.index()].clone()
                        } else {
                            vm::ImportedFunc {
                                func: module
                                    .func_resolver
                                    .get(module, func_index)
                                    .unwrap()
                                    .as_ptr(),
                            }
                        };

                        elements[init.offset + i] = vm::Anyfunc {
                            func_data,
                            sig_id: vm_sig_id,
                        };
                    }
                }
            }
        }

        tables
            .iter_mut()
            .map(|table| table.into_vm_table())
            .collect::<Vec<_>>()
            .into_boxed_slice()
    }

    fn generate_globals(module: &Module) -> Box<[vm::LocalGlobal]> {
        let globals = vec![vm::LocalGlobal::null(); module.globals.len()];

        globals.into_boxed_slice()
    }

    fn finalize_globals(
        module: &Module,
        imports: &ImportBacking,
        mut globals: Box<[vm::LocalGlobal]>,
    ) -> Box<[vm::LocalGlobal]> {
        for (to, (_, from)) in globals.iter_mut().zip(module.globals.into_iter()) {
            to.data = match from.init {
                Initializer::Const(Value::I32(x)) => x as u64,
                Initializer::Const(Value::I64(x)) => x as u64,
                Initializer::Const(Value::F32(x)) => x as u64,
                Initializer::Const(Value::F64(x)) => x,
                Initializer::GetGlobal(index) => (imports.globals[index.index()].global).data,
            };
        }

        globals
    }

    // fn generate_tables(module: &Module, _options: &InstanceOptions) -> (Box<[TableBacking]>, Box<[vm::LocalTable]>) {
    //     let mut tables = Vec::new();
    //     // Reserve space for tables
    //     tables.reserve_exact(module.info.tables.len());

    //     // Get tables in module
    //     for table in &module.info.tables {
    //         let table: Vec<usize> = match table.import_name.as_ref() {
    //             Some((module_name, field_name)) => {
    //                 let imported =
    //                     import_object.get(&module_name.as_str(), &field_name.as_str());
    //                 match imported {
    //                     Some(ImportValue::Table(t)) => t.to_vec(),
    //                     None => {
    //                         if options.mock_missing_tables {
    //                             debug!(
    //                                 "The Imported table {}.{} is not provided, therefore will be mocked.",
    //                                 module_name, field_name
    //                             );
    //                             let len = table.entity.minimum as usize;
    //                             let mut v = Vec::with_capacity(len);
    //                             v.resize(len, 0);
    //                             v
    //                         } else {
    //                             panic!(
    //                                 "Imported table value was not provided ({}.{})",
    //                                 module_name, field_name
    //                             )
    //                         }
    //                     }
    //                     _ => panic!(
    //                         "Expected global table, but received {:?} ({}.{})",
    //                         imported, module_name, field_name
    //                     ),
    //                 }
    //             }
    //             None => {
    //                 let len = table.entity.minimum as usize;
    //                 let mut v = Vec::with_capacity(len);
    //                 v.resize(len, 0);
    //                 v
    //             }
    //         };
    //         tables.push(table);
    //     }

    //     // instantiate tables
    //     for table_element in &module.info.table_elements {
    //         let base = match table_element.base {
    //             Some(global_index) => globals_data[global_index.index()] as usize,
    //             None => 0,
    //         };

    //         let table = &mut tables[table_element.table_index.index()];
    //         for (i, func_index) in table_element.elements.iter().enumerate() {
    //             // since the table just contains functions in the MVP
    //             // we get the address of the specified function indexes
    //             // to populate the table.

    //             // let func_index = *elem_index - module.info.imported_funcs.len() as u32;
    //             // let func_addr = functions[func_index.index()].as_ptr();
    //             let func_addr = get_function_addr(&func_index, &import_functions, &functions);
    //             table[base + table_element.offset + i] = func_addr as _;
    //         }
    //     }
    // }
}

#[derive(Debug)]
pub struct ImportBacking {
    pub functions: Box<[vm::ImportedFunc]>,
    pub memories: Box<[vm::ImportedMemory]>,
    pub tables: Box<[vm::ImportedTable]>,
    pub globals: Box<[vm::ImportedGlobal]>,
}

impl ImportBacking {
    pub fn new(module: &Module, imports: &dyn ImportResolver) -> Result<Self, String> {
        assert!(
            module.imported_memories.len() == 0,
            "imported memories not yet supported"
        );
        assert!(
            module.imported_tables.len() == 0,
            "imported tables not yet supported"
        );

        let mut functions = Vec::with_capacity(module.imported_functions.len());
        for (
            index,
            ImportName {
                module: mod_name,
                name: item_name,
            },
        ) in &module.imported_functions
        {
            let sig_index = module.func_assoc[index];
            let expected_sig = module.sig_registry.lookup_func_sig(sig_index);
            let import = imports.get(mod_name, item_name);
            match import {
                Some(&Import::Func(func, ref signature)) => {
                    if expected_sig == signature {
                        functions.push(vm::ImportedFunc {
                            func,
                            // vmctx: ptr::null_mut(),
                        });
                    } else {
                        return Err(format!(
                            "unexpected signature for {:?}:{:?}",
                            mod_name, item_name
                        ));
                    }
                }
                Some(_) => {
                    return Err(format!(
                        "incorrect import type for {}:{}",
                        mod_name, item_name
                    ));
                }
                None => {
                    return Err(format!("import not found: {}:{}", mod_name, item_name));
                }
            }
        }

        let mut globals = Vec::with_capacity(module.imported_globals.len());
        for (
            _,
            (
                ImportName {
                    module: mod_name,
                    name: item_name,
                },
                global_desc,
            ),
        ) in &module.imported_globals
        {
            let import = imports.get(mod_name, item_name);
            match import {
                Some(Import::Global(val)) => {
                    if val.ty() == global_desc.ty {
                        globals.push(vm::ImportedGlobal {
                            global: vm::LocalGlobal {
                                data: match val {
                                    Value::I32(n) => *n as u64,
                                    Value::I64(n) => *n as u64,
                                    Value::F32(n) => *n as u64,
                                    Value::F64(n) => *n,
                                },
                            },
                        });
                    } else {
                        return Err(format!(
                            "unexpected global type for {:?}:{:?}",
                            mod_name, item_name
                        ));
                    }
                }
                Some(_) => {
                    return Err(format!(
                        "incorrect import type for {}:{}",
                        mod_name, item_name
                    ));
                }
                None => {
                    return Err(format!("import not found: {}:{}", mod_name, item_name));
                }
            }
        }

        Ok(ImportBacking {
            functions: functions.into_boxed_slice(),
            memories: vec![].into_boxed_slice(),
            tables: vec![].into_boxed_slice(),
            globals: globals.into_boxed_slice(),
        })
    }
}