// Copyright 2021-2024 Vector 35 Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

use std::path::PathBuf;
use std::{
    collections::HashMap,
    ops::Deref,
    sync::mpsc,
    str::FromStr
};

use crate::{DebugInfoBuilderContext, ReaderType};
use binaryninja::binaryview::BinaryViewBase;
use binaryninja::filemetadata::FileMetadata;
use binaryninja::Endianness;
use binaryninja::{binaryview::{BinaryView, BinaryViewExt}, downloadprovider::{DownloadInstanceInputOutputCallbacks, DownloadProvider}, rc::Ref, settings::Settings};
use gimli::Dwarf;
use gimli::{
    constants, Attribute, AttributeValue,
    AttributeValue::{DebugInfoRef, DebugInfoRefSup, UnitRef},
    DebuggingInformationEntry, Operation, Unit, UnitOffset, UnitSectionOffset,
};

use log::warn;

pub(crate) fn get_uid<R: ReaderType>(
    dwarf: &Dwarf<R>,
    unit: &Unit<R>,
    entry: &DebuggingInformationEntry<R>,
) -> usize {
    // We set a large gap between supplementary and main entries
    let adj = dwarf.sup().map_or(0, |_| 0x1000000000000000);
    let entry_offset = match entry.offset().to_unit_section_offset(unit) {
        UnitSectionOffset::DebugInfoOffset(o) => o.0,
        UnitSectionOffset::DebugTypesOffset(o) => o.0,
    };
    entry_offset + adj
}

////////////////////////////////////
// DIE attr convenience functions

pub(crate) enum DieReference<'a, R: ReaderType> {
    UnitAndOffset((&'a Dwarf<R>, &'a Unit<R>, UnitOffset)),
    Err,
}

pub(crate) fn get_attr_die<'a, R: ReaderType>(
    dwarf: &'a Dwarf<R>,
    unit: &'a Unit<R>,
    entry: &DebuggingInformationEntry<R>,
    debug_info_builder_context: &'a DebugInfoBuilderContext<R>,
    attr: constants::DwAt,
) -> Option<DieReference<'a, R>> {
    match entry.attr_value(attr) {
        Ok(Some(UnitRef(offset))) => Some(DieReference::UnitAndOffset((dwarf, unit, offset))),
        Ok(Some(DebugInfoRef(offset))) => {
            if dwarf.sup().is_some() {
                for source_unit in debug_info_builder_context.units() {
                    if let Some(new_offset) = offset.to_unit_offset(&source_unit.header) {
                        return Some(DieReference::UnitAndOffset((dwarf, source_unit, new_offset)));
                    }
                }
            }
            else {
                // This could either have no supplementary file because it is one or because it just doesn't have one
                // operate on supplementary file if dwarf is a supplementary file, else self

                // It's possible this is a reference in the supplementary file to itself
                for source_unit in debug_info_builder_context.sup_units() {
                    if let Some(new_offset) = offset.to_unit_offset(&source_unit.header) {
                        return Some(DieReference::UnitAndOffset((dwarf, source_unit, new_offset)));
                    }
                }

                // ... or it just doesn't have a supplementary file
                for source_unit in debug_info_builder_context.units() {
                    if let Some(new_offset) = offset.to_unit_offset(&source_unit.header) {
                        return Some(DieReference::UnitAndOffset((dwarf, source_unit, new_offset)));
                    }
                }
            }

            None
        },
        Ok(Some(DebugInfoRefSup(offset))) => {
            for source_unit in debug_info_builder_context.sup_units() {
                if let Some(new_offset) = offset.to_unit_offset(&source_unit.header) {
                    return Some(DieReference::UnitAndOffset((dwarf.sup().unwrap(), source_unit, new_offset)));
                }
            }
            warn!("Failed to fetch DIE. Supplementary debug information may be incomplete.");
            None
        },
        _ => None,
    }
}

pub(crate) fn resolve_specification<'a, R: ReaderType>(
    dwarf: &'a Dwarf<R>,
    unit: &'a Unit<R>,
    entry: &DebuggingInformationEntry<R>,
    debug_info_builder_context: &'a DebugInfoBuilderContext<R>,
) -> DieReference<'a, R> {
    if let Some(die_reference) = get_attr_die(
        dwarf,
        unit,
        entry,
        debug_info_builder_context,
        constants::DW_AT_specification,
    ) {
        match die_reference {
            DieReference::UnitAndOffset((dwarf, entry_unit, entry_offset)) => {
                if let Ok(entry) = entry_unit.entry(entry_offset) {
                    resolve_specification(dwarf, entry_unit, &entry, debug_info_builder_context)
                } else {
                    warn!("Failed to fetch DIE for attr DW_AT_specification. Debug information may be incomplete.");
                    DieReference::Err
                }
            }
            DieReference::Err => DieReference::Err,
        }
    } else if let Some(die_reference) = get_attr_die(
        dwarf,
        unit,
        entry,
        debug_info_builder_context,
        constants::DW_AT_abstract_origin,
    ) {
        match die_reference {
            DieReference::UnitAndOffset((dwarf, entry_unit, entry_offset)) => {
                if entry_offset == entry.offset() && unit.header.offset() == entry_unit.header.offset() {
                    warn!("DWARF information is invalid (infinite abstract origin reference cycle). Debug information may be incomplete.");
                    DieReference::Err
                } else if let Ok(new_entry) = entry_unit.entry(entry_offset) {
                    resolve_specification(dwarf, entry_unit, &new_entry, debug_info_builder_context)
                } else {
                    warn!("Failed to fetch DIE for attr DW_AT_abstract_origin. Debug information may be incomplete.");
                    DieReference::Err
                }
            }
            DieReference::Err => DieReference::Err,
        }
    } else {
        DieReference::UnitAndOffset((dwarf, unit, entry.offset()))
    }
}

// Get name from DIE, or referenced dependencies
pub(crate) fn get_name<R: ReaderType>(
    dwarf: &Dwarf<R>,
    unit: &Unit<R>,
    entry: &DebuggingInformationEntry<R>,
    debug_info_builder_context: &DebugInfoBuilderContext<R>,
) -> Option<String> {
    match resolve_specification(dwarf, unit, entry, debug_info_builder_context) {
        DieReference::UnitAndOffset((dwarf, entry_unit, entry_offset)) => {
            if let Ok(Some(attr_val)) = entry_unit
                .entry(entry_offset)
                .unwrap()
                .attr_value(constants::DW_AT_name)
            {
                if let Ok(attr_string) = dwarf.attr_string(entry_unit, attr_val.clone())
                {
                    if let Ok(attr_string) = attr_string.to_string() {
                        return Some(attr_string.to_string());
                    }
                }
                else if let Some(dwarf) = &dwarf.sup {
                    if let Ok(attr_string) = dwarf.attr_string(entry_unit, attr_val)
                    {
                        if let Ok(attr_string) = attr_string.to_string() {
                            return Some(attr_string.to_string());
                        }
                    }
                }
            }

            // if let Some(raw_name) = get_raw_name(unit, entry, debug_info_builder_context) {
            //     if let Some(arch) = debug_info_builder_context.default_architecture() {
            //         if let Ok((_, names)) = demangle_gnu3(&arch, raw_name, true) {
            //             return Some(names.join("::"));
            //         }
            //     }
            // }
            None
        }
        DieReference::Err => None,
    }
}

// Get raw name from DIE, or referenced dependencies
pub(crate) fn get_raw_name<R: ReaderType>(
    dwarf: &Dwarf<R>,
    unit: &Unit<R>,
    entry: &DebuggingInformationEntry<R>,
) -> Option<String> {
    if let Ok(Some(attr_val)) = entry.attr_value(constants::DW_AT_linkage_name) {
        if let Ok(attr_string) = dwarf.attr_string(unit, attr_val.clone())
        {
            if let Ok(attr_string) = attr_string.to_string() {
                return Some(attr_string.to_string());
            }
        }
        else if let Some(dwarf) = dwarf.sup() {
            if let Ok(attr_string) = dwarf.attr_string(unit, attr_val)
            {
                if let Ok(attr_string) = attr_string.to_string() {
                    return Some(attr_string.to_string());
                }
            }
        }
    }
    None
}

// Get the size of an object as a usize
pub(crate) fn get_size_as_usize<R: ReaderType>(
    entry: &DebuggingInformationEntry<R>,
) -> Option<usize> {
    if let Ok(Some(attr)) = entry.attr(constants::DW_AT_byte_size) {
        get_attr_as_usize(attr)
    } else if let Ok(Some(attr)) = entry.attr(constants::DW_AT_bit_size) {
        get_attr_as_usize(attr).map(|attr_value| attr_value / 8)
    } else {
        None
    }
}

// Get the size of an object as a u64
pub(crate) fn get_size_as_u64<R: ReaderType>(
    entry: &DebuggingInformationEntry<R>,
) -> Option<u64> {
    if let Ok(Some(attr)) = entry.attr(constants::DW_AT_byte_size) {
        get_attr_as_u64(&attr)
    } else if let Ok(Some(attr)) = entry.attr(constants::DW_AT_bit_size) {
        get_attr_as_u64(&attr).map(|attr_value| attr_value / 8)
    } else {
        None
    }
}

// Get the size of a subrange as a u64
pub(crate) fn get_subrange_size<R: ReaderType>(
    entry: &DebuggingInformationEntry<R>,
) -> u64 {
    if let Ok(Some(attr)) = entry.attr(constants::DW_AT_upper_bound) {
        get_attr_as_u64(&attr).map_or(0, |v| v + 1)
    } else if let Ok(Some(attr)) = entry.attr(constants::DW_AT_count) {
        get_attr_as_u64(&attr).unwrap_or(0)
    } else if let Ok(Some(attr)) = entry.attr(constants::DW_AT_lower_bound) {
        get_attr_as_u64(&attr).map_or(0, |v| v + 1)
    } else {
        0
    }
}

// Get the start address of a function
pub(crate) fn get_start_address<R: ReaderType>(
    dwarf: &Dwarf<R>,
    unit: &Unit<R>,
    entry: &DebuggingInformationEntry<R>,
) -> Option<u64> {
    if let Ok(Some(attr_val)) = entry.attr_value(constants::DW_AT_low_pc) {
        match dwarf.attr_address(unit, attr_val)
        {
            Ok(Some(val)) => Some(val),
            _ => None,
        }
    } else if let Ok(Some(attr_val)) = entry.attr_value(constants::DW_AT_entry_pc) {
        match dwarf.attr_address(unit, attr_val)
        {
            Ok(Some(val)) => Some(val),
            _ => None,
        }
    } else if let Ok(Some(attr_value)) = entry.attr_value(constants::DW_AT_ranges) {
        if let Ok(Some(ranges_offset)) = dwarf.attr_ranges_offset(unit, attr_value)
        {
            if let Ok(mut ranges) = dwarf.ranges(unit, ranges_offset)
            {
                if let Ok(Some(range)) = ranges.next() {
                    return Some(range.begin);
                }
            }
        }
        return None;
    } else {
        None
    }
}

// Get an attribute value as a u64 if it can be coerced
pub(crate) fn get_attr_as_u64<R: ReaderType>(attr: &Attribute<R>) -> Option<u64> {
    if let Some(value) = attr.udata_value() {
        Some(value)
    } else if let Some(value) = attr.sdata_value() {
        Some(value as u64)
    } else if let AttributeValue::Block(mut data) = attr.value() {
        match data.len() {
            1 => data.read_u8().map(u64::from).ok(),
            2 => data.read_u16().map(u64::from).ok(),
            4 => data.read_u32().map(u64::from).ok(),
            8 => data.read_u64().ok(),
            _ => None
        }
    } else {
        None
    }
}

// Get an attribute value as a usize if it can be coerced
pub(crate) fn get_attr_as_usize<R: ReaderType>(attr: Attribute<R>) -> Option<usize> {
    if let Some(value) = attr.u8_value() {
        Some(value.into())
    } else if let Some(value) = attr.u16_value() {
        Some(value.into())
    } else if let Some(value) = attr.udata_value() {
        Some(value as usize)
    } else {
        attr.sdata_value().map(|value| value as usize)
    }
}

// Get an attribute value as a usize if it can be coerced
// Parses DW_OP_address, DW_OP_const
pub(crate) fn get_expr_value<R: ReaderType>(
    unit: &Unit<R>,
    attr: Attribute<R>,
) -> Option<u64> {
    if let AttributeValue::Exprloc(mut expression) = attr.value() {
        match Operation::parse(&mut expression.0, unit.encoding()) {
            Ok(Operation::PlusConstant { value }) => Some(value),
            Ok(Operation::UnsignedConstant { value }) => Some(value),
            Ok(Operation::Address { address: 0 }) => None,
            Ok(Operation::Address { address }) => Some(address),
            _ => None
        }
    } else {
        None
    }
}


pub(crate) fn get_build_id(view: &BinaryView) -> Result<String, String> {
    let mut build_id: Option<String> = None;

    if let Ok(raw_view) = view.raw_view() {
        if let Ok(build_id_section) = raw_view.section_by_name(".note.gnu.build-id") {
            // Name size - 4 bytes
            // Desc size - 4 bytes
            // Type - 4 bytes
            // Name - n bytes
            // Desc - n bytes
            let build_id_bytes = raw_view.read_vec(build_id_section.start(), build_id_section.len());
            if build_id_bytes.len() < 12 {
                return Err("Build id section must be at least 12 bytes".to_string());
            }

            let name_len: u32;
            let desc_len: u32;
            let note_type: u32;
            match raw_view.default_endianness() {
                Endianness::LittleEndian => {
                    name_len = u32::from_le_bytes(build_id_bytes[0..4].try_into().unwrap());
                    desc_len = u32::from_le_bytes(build_id_bytes[4..8].try_into().unwrap());
                    note_type = u32::from_le_bytes(build_id_bytes[8..12].try_into().unwrap());
                },
                Endianness::BigEndian => {
                    name_len = u32::from_be_bytes(build_id_bytes[0..4].try_into().unwrap());
                    desc_len = u32::from_be_bytes(build_id_bytes[4..8].try_into().unwrap());
                    note_type = u32::from_be_bytes(build_id_bytes[8..12].try_into().unwrap());
                }
            };

            if note_type != 3 {
                return Err(format!("Build id section has wrong type: {}", note_type));
            }

            let expected_len = (12 + name_len + desc_len) as usize;

            if build_id_bytes.len() < expected_len {
                return Err(format!("Build id section not expected length: expected {}, got {}", expected_len, build_id_bytes.len()));
            }

            let desc: &[u8] = &build_id_bytes[(12+name_len as usize)..expected_len];
            build_id = Some(desc.iter().map(|b| format!("{:02x}", b)).collect());
        }
    }

    if let Some(x) = build_id {
        Ok(x)
    }
    else {
        Err("Failed to get build id".to_string())
    }
}


pub(crate) fn download_debug_info(build_id: &String, view: &BinaryView) -> Result<Ref<BinaryView>, String> {
    let settings = Settings::new("");

    let debug_server_urls = settings.get_string_list("network.debuginfodServers", Some(view), None);

    for debug_server_url in debug_server_urls.iter() {
        let artifact_url = format!("{}/buildid/{}/debuginfo", debug_server_url, build_id);

        // Download from remote
        let (tx, rx) = mpsc::channel();
        let write = move |data: &[u8]| -> usize {
            if let Ok(_) = tx.send(Vec::from(data)) {
                data.len()
            } else {
                0
            }
        };

        let dp = DownloadProvider::try_default().map_err(|_| "No default download provider")?;
        let mut inst = dp
            .create_instance()
            .map_err(|_| "Couldn't create download instance")?;
        let result = inst
            .perform_custom_request(
                "GET",
                artifact_url,
                HashMap::<String, String>::new(),
                DownloadInstanceInputOutputCallbacks {
                    read: None,
                    write: Some(Box::new(write)),
                    progress: None,
                },
            )
            .map_err(|e| e.to_string())?;
        if result.status_code != 200 {
            continue;
        }

        let mut expected_length = None;
        for (k, v) in result.headers.iter() {
            if k.to_lowercase() == "content-length" {
                expected_length = Some(usize::from_str(v).map_err(|e| e.to_string())?);
            }
        }

        let mut data = vec![];
        while let Ok(packet) = rx.try_recv() {
            data.extend(packet.into_iter());
        }

        if let Some(length) = expected_length {
            if data.len() != length {
                return Err(format!(
                    "Bad length: expected {} got {}",
                    length,
                    data.len()
                ));
            }
        }

        let options = "{\"analysis.debugInfo.internal\": false}";
        let bv = BinaryView::from_data(FileMetadata::new().deref(), &data)
            .map_err(|_| "Unable to create binary view from downloaded data".to_string())?;

        return binaryninja::load_view(bv.deref(), false, Some(options))
            .ok_or("Unable to load binary view from downloaded data".to_string());
    }
    return Err("Could not find a server with debug info for this file".to_string());
}


pub(crate) fn find_local_debug_file(build_id: &String, view: &BinaryView) -> Option<String> {
    let settings = Settings::new("");
    let debug_info_paths = settings.get_string_list("analysis.debugInfo.debugDirectories", Some(view), None);

    if debug_info_paths.is_empty() {
        return None
    }

    for debug_info_path in debug_info_paths.into_iter() {
        if let Ok(path) = PathBuf::from_str(&debug_info_path.to_string())
        {
            let elf_path = path
                .join(&build_id[..2])
                .join(&build_id[2..])
                .join("elf");

            let debug_ext_path = path
                .join(&build_id[..2])
                .join(format!("{}.debug", &build_id[2..]));

            let final_path = if debug_ext_path.exists() {
                debug_ext_path
            }
            else if elf_path.exists() {
                elf_path
            }
            else {
                // No paths exist in this dir, try the next one
                continue;
            };
            return final_path
                .to_str()
                .and_then(|x| Some(x.to_string()));
        }
    }
    None
}


pub(crate) fn load_debug_info_for_build_id(build_id: &String, view: &BinaryView) -> (Option<Ref<BinaryView>>, bool) {
    if let Some(debug_file_path) = find_local_debug_file(build_id, view) {
        return
        (
            binaryninja::load_with_options(
                debug_file_path,
                false,
                Some("{\"analysis.debugInfo.internal\": false}")
            ),
            false
        );
    }
    else if Settings::new("").get_bool("network.enableDebuginfod", Some(view), None) {
        return (
            download_debug_info(build_id, view).ok(),
            true
        );
    }
    (None, false)
}