use std::future::Future;
use std::sync::Arc;

use uv_configuration::BuildOptions;
use uv_distribution::{ArchiveMetadata, DistributionDatabase};
use uv_distribution_types::{Dist, IndexCapabilities, IndexUrl};
use uv_normalize::PackageName;
use uv_pep440::{Version, VersionSpecifiers};
use uv_platform_tags::Tags;
use uv_types::{BuildContext, HashStrategy};

use crate::flat_index::FlatIndex;
use crate::version_map::VersionMap;
use crate::yanks::AllowedYanks;
use crate::{ExcludeNewer, RequiresPython};

pub type PackageVersionsResult = Result<VersionsResponse, uv_client::Error>;
pub type WheelMetadataResult = Result<MetadataResponse, uv_distribution::Error>;

/// The response when requesting versions for a package
#[derive(Debug)]
pub enum VersionsResponse {
    /// The package was found in the registry with the included versions
    Found(Vec<VersionMap>),
    /// The package was not found in the registry
    NotFound,
    /// The package was not found in the local registry
    NoIndex,
    /// The package was not found in the cache and the network is not available.
    Offline,
}

#[derive(Debug)]
pub enum MetadataResponse {
    /// The wheel metadata was found and parsed successfully.
    Found(ArchiveMetadata),
    /// The wheel metadata was not found.
    MissingMetadata,
    /// The wheel metadata was found, but could not be parsed.
    InvalidMetadata(Box<uv_pypi_types::MetadataError>),
    /// The wheel metadata was found, but the metadata was inconsistent.
    InconsistentMetadata(Box<uv_distribution::Error>),
    /// The wheel has an invalid structure.
    InvalidStructure(Box<uv_metadata::Error>),
    /// The wheel metadata was not found in the cache and the network is not available.
    Offline,
    /// The source distribution has a `requires-python` requirement that is not met by the installed
    /// Python version (and static metadata is not available).
    RequiresPython(VersionSpecifiers, Version),
    /// The distribution could not be built or downloaded.
    Error(Box<Dist>, Arc<uv_distribution::Error>),
}

pub trait ResolverProvider {
    /// Get the version map for a package.
    fn get_package_versions<'io>(
        &'io self,
        package_name: &'io PackageName,
        index: Option<&'io IndexUrl>,
    ) -> impl Future<Output = PackageVersionsResult> + 'io;

    /// Get the metadata for a distribution.
    ///
    /// For a wheel, this is done by querying it's (remote) metadata, for a source dist we
    /// (fetch and) build the source distribution and return the metadata from the built
    /// distribution.
    fn get_or_build_wheel_metadata<'io>(
        &'io self,
        dist: &'io Dist,
    ) -> impl Future<Output = WheelMetadataResult> + 'io;

    /// Set the [`uv_distribution::Reporter`] to use for this installer.
    #[must_use]
    fn with_reporter(self, reporter: impl uv_distribution::Reporter + 'static) -> Self;
}

/// The main IO backend for the resolver, which does cached requests network requests using the
/// [`RegistryClient`] and [`DistributionDatabase`].
pub struct DefaultResolverProvider<'a, Context: BuildContext> {
    /// The [`DistributionDatabase`] used to build source distributions.
    fetcher: DistributionDatabase<'a, Context>,
    /// These are the entries from `--find-links` that act as overrides for index responses.
    flat_index: FlatIndex,
    tags: Option<Tags>,
    requires_python: RequiresPython,
    allowed_yanks: AllowedYanks,
    hasher: HashStrategy,
    exclude_newer: Option<ExcludeNewer>,
    build_options: &'a BuildOptions,
    capabilities: &'a IndexCapabilities,
}

impl<'a, Context: BuildContext> DefaultResolverProvider<'a, Context> {
    /// Reads the flat index entries and builds the provider.
    pub fn new(
        fetcher: DistributionDatabase<'a, Context>,
        flat_index: &'a FlatIndex,
        tags: Option<&'a Tags>,
        requires_python: &'a RequiresPython,
        allowed_yanks: AllowedYanks,
        hasher: &'a HashStrategy,
        exclude_newer: Option<ExcludeNewer>,
        build_options: &'a BuildOptions,
        capabilities: &'a IndexCapabilities,
    ) -> Self {
        Self {
            fetcher,
            flat_index: flat_index.clone(),
            tags: tags.cloned(),
            requires_python: requires_python.clone(),
            allowed_yanks,
            hasher: hasher.clone(),
            exclude_newer,
            build_options,
            capabilities,
        }
    }
}

impl<'a, Context: BuildContext> ResolverProvider for DefaultResolverProvider<'a, Context> {
    /// Make a "Simple API" request for the package and convert the result to a [`VersionMap`].
    async fn get_package_versions<'io>(
        &'io self,
        package_name: &'io PackageName,
        index: Option<&'io IndexUrl>,
    ) -> PackageVersionsResult {
        let result = self
            .fetcher
            .client()
            .managed(|client| client.simple(package_name, index, self.capabilities))
            .await;

        match result {
            Ok(results) => Ok(VersionsResponse::Found(
                results
                    .into_iter()
                    .map(|(index, metadata)| {
                        VersionMap::from_metadata(
                            metadata,
                            package_name,
                            index,
                            self.tags.as_ref(),
                            &self.requires_python,
                            &self.allowed_yanks,
                            &self.hasher,
                            self.exclude_newer.as_ref(),
                            self.flat_index.get(package_name).cloned(),
                            self.build_options,
                        )
                    })
                    .collect(),
            )),
            Err(err) => match err.into_kind() {
                uv_client::ErrorKind::PackageNotFound(_) => {
                    if let Some(flat_index) = self.flat_index.get(package_name).cloned() {
                        Ok(VersionsResponse::Found(vec![VersionMap::from(flat_index)]))
                    } else {
                        Ok(VersionsResponse::NotFound)
                    }
                }
                uv_client::ErrorKind::NoIndex(_) => {
                    if let Some(flat_index) = self.flat_index.get(package_name).cloned() {
                        Ok(VersionsResponse::Found(vec![VersionMap::from(flat_index)]))
                    } else if self.flat_index.offline() {
                        Ok(VersionsResponse::Offline)
                    } else {
                        Ok(VersionsResponse::NoIndex)
                    }
                }
                uv_client::ErrorKind::Offline(_) => {
                    if let Some(flat_index) = self.flat_index.get(package_name).cloned() {
                        Ok(VersionsResponse::Found(vec![VersionMap::from(flat_index)]))
                    } else {
                        Ok(VersionsResponse::Offline)
                    }
                }
                kind => Err(kind.into()),
            },
        }
    }

    /// Fetch the metadata for a distribution, building it if necessary.
    async fn get_or_build_wheel_metadata<'io>(&'io self, dist: &'io Dist) -> WheelMetadataResult {
        match self
            .fetcher
            .get_or_build_wheel_metadata(dist, self.hasher.get(dist))
            .await
        {
            Ok(metadata) => Ok(MetadataResponse::Found(metadata)),
            Err(err) => match err {
                uv_distribution::Error::Client(client) => match client.into_kind() {
                    uv_client::ErrorKind::Offline(_) => Ok(MetadataResponse::Offline),
                    uv_client::ErrorKind::MetadataParseError(_, _, err) => {
                        Ok(MetadataResponse::InvalidMetadata(err))
                    }
                    uv_client::ErrorKind::Metadata(_, err) => {
                        Ok(MetadataResponse::InvalidStructure(Box::new(err)))
                    }
                    kind => Err(uv_client::Error::from(kind).into()),
                },
                uv_distribution::Error::WheelMetadataVersionMismatch { .. } => {
                    Ok(MetadataResponse::InconsistentMetadata(Box::new(err)))
                }
                uv_distribution::Error::WheelMetadataNameMismatch { .. } => {
                    Ok(MetadataResponse::InconsistentMetadata(Box::new(err)))
                }
                uv_distribution::Error::Metadata(err) => {
                    Ok(MetadataResponse::InvalidMetadata(Box::new(err)))
                }
                uv_distribution::Error::WheelMetadata(_, err) => {
                    Ok(MetadataResponse::InvalidStructure(err))
                }
                uv_distribution::Error::RequiresPython(requires_python, version) => {
                    Ok(MetadataResponse::RequiresPython(requires_python, version))
                }
                err => Ok(MetadataResponse::Error(
                    Box::new(dist.clone()),
                    Arc::new(err),
                )),
            },
        }
    }

    /// Set the [`uv_distribution::Reporter`] to use for this installer.
    #[must_use]
    fn with_reporter(self, reporter: impl uv_distribution::Reporter + 'static) -> Self {
        Self {
            fetcher: self.fetcher.with_reporter(reporter),
            ..self
        }
    }
}