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use std::env;

use sentry_core::protocol::{DebugImage, SymbolicDebugImage};
use sentry_core::types::{CodeId, DebugId, Uuid};

use findshlibs::{SharedLibrary, SharedLibraryId, TargetSharedLibrary, TARGET_SUPPORTED};

const UUID_SIZE: usize = 16;

/// Converts an ELF object identifier into a `DebugId`.
///
/// The identifier data is first truncated or extended to match 16 byte size of
/// Uuids. If the data is declared in little endian, the first three Uuid fields
/// are flipped to match the big endian expected by the breakpad processor.
///
/// The `DebugId::appendix` field is always `0` for ELF.
fn debug_id_from_build_id(build_id: &[u8]) -> Option<DebugId> {
    let mut data = [0u8; UUID_SIZE];
    let len = build_id.len().min(UUID_SIZE);
    data[0..len].copy_from_slice(&build_id[0..len]);

    #[cfg(target_endian = "little")]
    {
        // The ELF file targets a little endian architecture. Convert to
        // network byte order (big endian) to match the Breakpad processor's
        // expectations. For big endian object files, this is not needed.
        data[0..4].reverse(); // uuid field 1
        data[4..6].reverse(); // uuid field 2
        data[6..8].reverse(); // uuid field 3
    }

    Uuid::from_slice(&data).map(DebugId::from_uuid).ok()
}

/// Returns the list of loaded libraries/images.
pub fn debug_images() -> Vec<DebugImage> {
    let mut images = vec![];
    if !TARGET_SUPPORTED {
        return images;
    }

    TargetSharedLibrary::each(|shlib| {
        let maybe_debug_id = shlib.debug_id().and_then(|id| match id {
            SharedLibraryId::Uuid(bytes) => Some(DebugId::from_uuid(Uuid::from_bytes(bytes))),
            SharedLibraryId::GnuBuildId(ref id) => debug_id_from_build_id(id),
            SharedLibraryId::PdbSignature(guid, age) => DebugId::from_guid_age(&guid, age).ok(),
            _ => None,
        });

        let debug_id = match maybe_debug_id {
            Some(debug_id) => debug_id,
            None => return,
        };

        let mut name = shlib.name().to_string_lossy().to_string();
        if name.is_empty() {
            name = env::current_exe()
                .map(|x| x.display().to_string())
                .unwrap_or_else(|_| "<main>".to_string());
        }

        let code_id = shlib.id().map(|id| CodeId::new(format!("{}", id)));
        let debug_name = shlib.debug_name().map(|n| n.to_string_lossy().to_string());

        // For windows, the `virtual_memory_bias` actually returns the real
        // `module_base`, which is the address that sentry uses for symbolication.
        // Going via the segments means that the `image_addr` would be offset in
        // a way that symbolication yields wrong results.
        let (image_addr, image_vmaddr) = if cfg!(windows) {
            (shlib.virtual_memory_bias().0.into(), 0.into())
        } else {
            (
                shlib.actual_load_addr().0.into(),
                shlib.stated_load_addr().0.into(),
            )
        };

        images.push(
            SymbolicDebugImage {
                id: debug_id,
                name,
                arch: None,
                image_addr,
                image_size: shlib.len() as u64,
                image_vmaddr,
                code_id,
                debug_file: debug_name,
            }
            .into(),
        );
    });

    images
}