cargo-msrv 0.18.0

use camino::Utf8PathBuf;
use cargo_metadata::MetadataCommand;
use std::convert::TryFrom;

use rust_releases::{Release, ReleaseIndex};

use crate::compatibility::IsCompatible;
use crate::context::{EnvironmentContext, VerifyContext};
use crate::error::{CargoMSRVError, TResult};
use crate::manifest::bare_version::BareVersion;
use crate::manifest::CargoManifest;
use crate::outcome::Compatibility;
use crate::reporter::event::VerifyResult;
use crate::reporter::Reporter;
use crate::rust::Toolchain;
use crate::sub_command::SubCommand;

/// Verifier which determines whether a given Rust version is deemed compatible or not.
pub struct Verify<'index, C: IsCompatible> {
    release_index: &'index ReleaseIndex,
    runner: C,
}

impl<'index, C: IsCompatible> Verify<'index, C> {
    /// Instantiate the verifier using a release index and a runner.
    ///
    /// The runner is used to determine whether a given Rust version will be deemed compatible or not.
    pub fn new(release_index: &'index ReleaseIndex, runner: C) -> Self {
        Self {
            release_index,
            runner,
        }
    }
}

impl<C: IsCompatible> SubCommand for Verify<'_, C> {
    type Context = VerifyContext;
    type Output = ();

    /// Run the verifier against a Rust version which is obtained from the config.
    fn run(&self, ctx: &Self::Context, reporter: &impl Reporter) -> TResult<Self::Output> {
        // todo!
        let rust_version = ctx.rust_version.clone();

        verify_msrv(
            reporter,
            ctx,
            self.release_index,
            rust_version,
            &self.runner,
        )?;

        Ok(())
    }
}

/// Verify whether a Cargo project is compatible with a `rustup run` command,
/// for the (given or specified) `rust_version`.
fn verify_msrv(
    reporter: &impl Reporter,
    ctx: &VerifyContext,
    release_index: &ReleaseIndex,
    rust_version: RustVersion,
    runner: &impl IsCompatible,
) -> TResult<()> {
    let bare_version = rust_version.version();
    let version =
        bare_version.try_to_semver(release_index.releases().iter().map(Release::version))?;

    let target = ctx.toolchain.target;
    let components = ctx.toolchain.components;
    let toolchain = Toolchain::new(version.clone(), target, components);

    match runner.is_compatible(&toolchain)? {
        Compatibility::Compatible(_) => success(reporter, toolchain),
        Compatibility::Incompatible(f) => {
            failure(reporter, toolchain, rust_version, Some(f.error_message))
        }
    }
}

// Report the successful verification to the user
fn success(reporter: &impl Reporter, toolchain: Toolchain) -> TResult<()> {
    reporter.report_event(VerifyResult::compatible(toolchain))?;
    Ok(())
}

// Report the failed verification to the user, and return a VerifyFailed error
fn failure(
    reporter: &impl Reporter,
    toolchain: Toolchain,
    rust_version: RustVersion,
    error: Option<String>,
) -> TResult<()> {
    reporter.report_event(VerifyResult::incompatible(toolchain, error))?;

    Err(CargoMSRVError::SubCommandVerify(Error::VerifyFailed(
        VerifyFailed::from(rust_version),
    )))
}

/// Error which can be returned if the verifier deemed the tested Rust version incompatible.
#[derive(Debug, thiserror::Error)]
pub enum Error {
    #[error(
        "Crate source was found to be incompatible with Rust version '{}' specified {}", .0.rust_version, .0.source
    )]
    VerifyFailed(VerifyFailed),
}

/// Data structure which contains information about which version failed to verify, and where
/// we obtained this version from.
///
/// It is combination of the Rust version which was tested for compatibility and the source which was
/// used to find this tested Rust version.
#[derive(Debug)]
pub struct VerifyFailed {
    rust_version: BareVersion,
    source: RustVersionSource,
}

impl From<RustVersion> for VerifyFailed {
    fn from(value: RustVersion) -> Self {
        VerifyFailed {
            rust_version: value.rust_version,
            source: value.source,
        }
    }
}

/// A combination of a bare (two- or three component) Rust version and the source which was used to
/// locate this version.
#[derive(Clone, Debug)]
pub struct RustVersion {
    rust_version: BareVersion,
    source: RustVersionSource,
}

impl RustVersion {
    pub fn from_arg(rust_version: BareVersion) -> Self {
        Self {
            rust_version,
            source: RustVersionSource::Arg,
        }
    }

    pub fn try_from_environment(env: &EnvironmentContext) -> TResult<Self> {
        let manifest_path = env.manifest();

        let metadata = MetadataCommand::new()
            .manifest_path(&manifest_path)
            .exec()?;
        CargoManifest::try_from(metadata)?
            .minimum_rust_version()
            .ok_or_else(|| CargoMSRVError::NoMSRVKeyInCargoToml(manifest_path.clone()))
            .map(|v| RustVersion {
                rust_version: v.clone(),
                source: RustVersionSource::Manifest(manifest_path.clone()),
            })
    }

    /// Get the bare (two- or three component) version specifying the Rust version.
    pub fn version(&self) -> &BareVersion {
        &self.rust_version
    }

    /// Get the version and discard all else.
    pub fn into_version(self) -> BareVersion {
        self.rust_version
    }
}

/// Source used to obtain a Rust version for the verifier.
#[derive(Clone, Debug, thiserror::Error)]
enum RustVersionSource {
    #[error("as --rust-version argument")]
    Arg,

    #[error("as MSRV in the Cargo manifest located at '{0}'")]
    Manifest(Utf8PathBuf),
}