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//! # crate2nix
//!
//! Internal library for the crate2nix binary. This is not meant to be used separately, I just enjoy
//! writing doc tests ;)

//#![deny(missing_docs)]

use std::collections::{BTreeMap, HashSet, VecDeque};
use std::env;
use std::path::PathBuf;

use cargo_metadata::Metadata;
use cargo_metadata::PackageId;
use failure::format_err;
use failure::Error;
use serde::Deserialize;
use serde::Serialize;

use crate::metadata::IndexedMetadata;
use crate::resolve::CrateDerivation;

mod metadata;
pub mod nix_build;
mod prefetch;
pub mod render;
mod resolve;
mod target_cfg;
pub mod util;

/// The resolved build info and the input for rendering the build.nix.tera template.
#[derive(Debug, Deserialize, Serialize)]
pub struct BuildInfo {
    // The package ID of the root crate.
    pub root_package_id: Option<PackageId>,
    // Workspaces member package IDs by package names.
    pub workspace_members: BTreeMap<String, PackageId>,
    // Build info for all crates needed for this build.
    pub crates: Vec<CrateDerivation>,
    // For convenience include the source for tests.
    pub indexed_metadata: IndexedMetadata,
    // The generation configuration.
    pub info: GenerateInfo,
    // The generation configuration.
    pub config: GenerateConfig,
}

impl BuildInfo {
    /// Return the `NixBuildInfo` data ready for rendering the nix build file.
    pub fn for_config(info: &GenerateInfo, config: &GenerateConfig) -> Result<BuildInfo, Error> {
        let metadata = cargo_metadata(config)?;
        let indexed_metadata = IndexedMetadata::new_from(metadata).map_err(|e| {
            format_err!(
                "while indexing metadata for {}: {}",
                config.cargo_toml.to_string_lossy(),
                e
            )
        })?;
        let mut default_nix = BuildInfo::new(info, config, indexed_metadata)?;

        default_nix.prune_unneeded_crates();

        prefetch_and_fill_crates_sha256(config, &mut default_nix)?;

        Ok(default_nix)
    }

    fn prune_unneeded_crates(&mut self) {
        let mut queue: VecDeque<&PackageId> = self
            .root_package_id
            .iter()
            .chain(self.workspace_members.values())
            .collect();
        let mut reachable = HashSet::new();
        let indexed_crates: BTreeMap<_, _> =
            self.crates.iter().map(|c| (&c.package_id, c)).collect();
        while let Some(next_package_id) = queue.pop_back() {
            if !reachable.insert(next_package_id.clone()) {
                continue;
            }

            queue.extend(
                indexed_crates
                    .get(next_package_id)
                    .iter()
                    .flat_map(|c| c.dependencies.iter().chain(c.build_dependencies.iter()))
                    .map(|d| &d.package_id),
            );
        }
        self.crates.retain(|c| reachable.contains(&c.package_id));
    }

    fn new(
        info: &GenerateInfo,
        config: &GenerateConfig,
        metadata: IndexedMetadata,
    ) -> Result<BuildInfo, Error> {
        Ok(BuildInfo {
            root_package_id: metadata.root.clone(),
            workspace_members: metadata
                .workspace_members
                .iter()
                .flat_map(|pkg_id| {
                    metadata
                        .pkgs_by_id
                        .get(pkg_id)
                        .map(|pkg| (pkg.name.clone(), pkg_id.clone()))
                })
                .collect(),
            crates: metadata
                .pkgs_by_id
                .values()
                .map(|package| CrateDerivation::resolve(config, &metadata, package))
                .collect::<Result<_, Error>>()?,
            indexed_metadata: metadata,
            info: info.clone(),
            config: config.clone(),
        })
    }
}

/// Call `cargo metadata` and return result.
fn cargo_metadata(config: &GenerateConfig) -> Result<Metadata, Error> {
    let mut cmd = cargo_metadata::MetadataCommand::new();
    cmd.manifest_path(&config.cargo_toml)
        .other_options(&["--locked".into()]);
    cmd.exec().map_err(|e| {
        format_err!(
            "while retrieving metadata about {}: {}",
            &config.cargo_toml.to_string_lossy(),
            e
        )
    })
}

/// Call `nix-prefetch` to determine sha256 for crates from crates.io.
fn prefetch_and_fill_crates_sha256(
    config: &GenerateConfig,
    default_nix: &mut BuildInfo,
) -> Result<(), Error> {
    prefetch::prefetch(config, &mut default_nix.crates)
        .map_err(|e| format_err!("while prefetching crates for calculating sha256: {}", e))?;
    Ok(())
}

/// Some info about the crate2nix invocation.
#[derive(Debug, Deserialize, Serialize, Clone)]
pub struct GenerateInfo {
    pub crate2nix_version: String,
    pub crate2nix_arguments: Vec<String>,
}

impl Default for GenerateInfo {
    fn default() -> GenerateInfo {
        GenerateInfo {
            crate2nix_version: env!("CARGO_PKG_VERSION").to_string(),
            crate2nix_arguments: env::args().skip(1).collect(),
        }
    }
}

/// Configuration for the default.nix generation.
#[derive(Debug, Deserialize, Serialize, Clone)]
pub struct GenerateConfig {
    pub cargo_toml: PathBuf,
    pub output: PathBuf,
    pub crate_hashes_json: PathBuf,
    pub nixpkgs_path: String,
}