// Copyright (c) The nextest Contributors
// SPDX-License-Identifier: MIT OR Apache-2.0

//! Support for [target runners](https://doc.rust-lang.org/cargo/reference/config.html#targettriplerunner)

use crate::{
    cargo_config::{CargoConfig, CargoConfigSource, CargoConfigs, DiscoveredConfig, Runner},
    errors::TargetRunnerError,
    platform::BuildPlatforms,
};
use camino::{Utf8Path, Utf8PathBuf};
use nextest_metadata::BuildPlatform;
use std::fmt;
use target_spec::Platform;

/// A [target runner](https://doc.rust-lang.org/cargo/reference/config.html#targettriplerunner)
/// used to execute a test binary rather than the default of executing natively.
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct TargetRunner {
    host: Option<PlatformRunner>,
    target: Option<PlatformRunner>,
}

impl TargetRunner {
    /// Acquires the [target runner](https://doc.rust-lang.org/cargo/reference/config.html#targettriplerunner)
    /// which can be set in a [.cargo/config.toml](https://doc.rust-lang.org/cargo/reference/config.html#hierarchical-structure)
    /// or via a `CARGO_TARGET_{TRIPLE}_RUNNER` environment variable
    pub fn new(
        configs: &CargoConfigs,
        build_platforms: &BuildPlatforms,
    ) -> Result<Self, TargetRunnerError> {
        let host = PlatformRunner::by_precedence(configs, &build_platforms.host)?;
        let target = match &build_platforms.target {
            Some(target) => PlatformRunner::by_precedence(configs, &target.platform)?,
            None => host.clone(),
        };

        Ok(Self { host, target })
    }

    /// Creates an empty target runner that does not delegate to any runner binaries.
    pub fn empty() -> Self {
        Self {
            host: None,
            target: None,
        }
    }

    /// Returns the target [`PlatformRunner`].
    #[inline]
    pub fn target(&self) -> Option<&PlatformRunner> {
        self.target.as_ref()
    }

    /// Returns the host [`PlatformRunner`].
    #[inline]
    pub fn host(&self) -> Option<&PlatformRunner> {
        self.host.as_ref()
    }

    /// Returns the [`PlatformRunner`] for the given build platform (host or target).
    #[inline]
    pub fn for_build_platform(&self, build_platform: BuildPlatform) -> Option<&PlatformRunner> {
        match build_platform {
            BuildPlatform::Target => self.target(),
            BuildPlatform::Host => self.host(),
        }
    }

    /// Returns the platform runners for all build platforms.
    #[inline]
    pub fn all_build_platforms(&self) -> [(BuildPlatform, Option<&PlatformRunner>); 2] {
        [
            (BuildPlatform::Target, self.target()),
            (BuildPlatform::Host, self.host()),
        ]
    }
}

/// A target runner scoped to a specific platform (host or target).
///
/// This forms part of [`TargetRunner`].
#[derive(Clone, Debug, Eq, PartialEq)]
pub struct PlatformRunner {
    runner_binary: Utf8PathBuf,
    args: Vec<String>,
    source: PlatformRunnerSource,
}

impl PlatformRunner {
    fn by_precedence(
        configs: &CargoConfigs,
        platform: &Platform,
    ) -> Result<Option<Self>, TargetRunnerError> {
        Self::find_config(configs, platform)
    }

    /// Attempts to find a target runner for the specified target from a
    /// [cargo config](https://doc.rust-lang.org/cargo/reference/config.html#hierarchical-structure)
    ///
    /// Not part of the public API. For testing only.
    #[doc(hidden)]
    pub fn find_config(
        configs: &CargoConfigs,
        target: &Platform,
    ) -> Result<Option<Self>, TargetRunnerError> {
        // Now that we've found all of the config files that could declare
        // a runner that matches our target triple, we need to actually find
        // all the matches, but in reverse order as the closer the config is
        // to our current working directory, the higher precedence it has
        for discovered_config in configs.discovered_configs() {
            match discovered_config {
                DiscoveredConfig::CliOption { config, source }
                | DiscoveredConfig::File { config, source } => {
                    if let Some(runner) =
                        Self::from_cli_option_or_file(target, config, source, configs.cwd())?
                    {
                        return Ok(Some(runner));
                    }
                }
                DiscoveredConfig::Env => {
                    // Check if we have a CARGO_TARGET_{TRIPLE}_RUNNER environment variable
                    // set, and if so use that.
                    if let Some(tr) = Self::from_env(Self::runner_env_var(target), configs.cwd())? {
                        return Ok(Some(tr));
                    }
                }
            }
        }

        Ok(None)
    }

    fn from_cli_option_or_file(
        target: &target_spec::Platform,
        config: &CargoConfig,
        source: &CargoConfigSource,
        cwd: &Utf8Path,
    ) -> Result<Option<Self>, TargetRunnerError> {
        if let Some(targets) = &config.target {
            // First lookup by the exact triple, as that one always takes precedence
            if let Some(parent) = targets.get(target.triple_str()) {
                if let Some(runner) = &parent.runner {
                    return Ok(Some(Self::parse_runner(
                        PlatformRunnerSource::CargoConfig {
                            source: source.clone(),
                            target_table: target.triple_str().into(),
                        },
                        runner.clone(),
                        cwd,
                    )?));
                }
            }

            // Next check if there are target.'cfg(..)' expressions that match
            // the target. cargo states that it is not allowed for more than
            // 1 cfg runner to match the target, but we let cargo handle that
            // error itself, we just use the first one that matches
            for (cfg, runner) in targets.iter().filter_map(|(k, v)| match &v.runner {
                Some(runner) if k.starts_with("cfg(") => Some((k, runner)),
                _ => None,
            }) {
                // Treat these as non-fatal, but would be good to log maybe
                let expr = match target_spec::TargetSpecExpression::new(cfg) {
                    Ok(expr) => expr,
                    Err(_err) => continue,
                };

                if expr.eval(target) == Some(true) {
                    return Ok(Some(Self::parse_runner(
                        PlatformRunnerSource::CargoConfig {
                            source: source.clone(),
                            target_table: cfg.clone(),
                        },
                        runner.clone(),
                        cwd,
                    )?));
                }
            }
        }

        Ok(None)
    }

    fn from_env(env_key: String, cwd: &Utf8Path) -> Result<Option<Self>, TargetRunnerError> {
        if let Some(runner_var) = std::env::var_os(&env_key) {
            let runner = runner_var
                .into_string()
                .map_err(|_osstr| TargetRunnerError::InvalidEnvironmentVar(env_key.clone()))?;
            Self::parse_runner(
                PlatformRunnerSource::Env(env_key),
                Runner::Simple(runner),
                cwd,
            )
            .map(Some)
        } else {
            Ok(None)
        }
    }

    // Not part of the public API. Exposed for testing only.
    #[doc(hidden)]
    pub fn runner_env_var(target: &Platform) -> String {
        let triple_str = target.triple_str().to_ascii_uppercase().replace('-', "_");
        format!("CARGO_TARGET_{triple_str}_RUNNER")
    }

    fn parse_runner(
        source: PlatformRunnerSource,
        runner: Runner,
        cwd: &Utf8Path,
    ) -> Result<Self, TargetRunnerError> {
        let (runner_binary, args) = match runner {
            Runner::Simple(value) => {
                // We only split on whitespace, which doesn't take quoting into account,
                // but I believe that cargo doesn't do that either
                let mut runner_iter = value.split_whitespace();

                let runner_binary =
                    runner_iter
                        .next()
                        .ok_or_else(|| TargetRunnerError::BinaryNotSpecified {
                            key: source.clone(),
                            value: value.clone(),
                        })?;
                let args = runner_iter.map(String::from).collect();
                (
                    Self::normalize_runner(runner_binary, source.resolve_dir(cwd)),
                    args,
                )
            }
            Runner::List(mut values) => {
                if values.is_empty() {
                    return Err(TargetRunnerError::BinaryNotSpecified {
                        key: source,
                        value: String::new(),
                    });
                } else {
                    let runner_binary = values.remove(0);
                    (
                        Self::normalize_runner(&runner_binary, source.resolve_dir(cwd)),
                        values,
                    )
                }
            }
        };

        Ok(Self {
            runner_binary,
            args,
            source,
        })
    }

    // https://github.com/rust-lang/cargo/blob/40b674cd1115299034fafa34e7db3a9140b48a49/src/cargo/util/config/mod.rs#L735-L743
    fn normalize_runner(runner_binary: &str, resolve_dir: &Utf8Path) -> Utf8PathBuf {
        let is_path =
            runner_binary.contains('/') || (cfg!(windows) && runner_binary.contains('\\'));
        if is_path {
            resolve_dir.join(runner_binary)
        } else {
            // A pathless name.
            runner_binary.into()
        }
    }

    /// Gets the runner binary path.
    ///
    /// Note that this is returned as a `str` specifically to avoid duct's
    /// behavior of prepending `.` to paths it thinks are relative, the path
    /// specified for a runner can be a full path, but it is most commonly a
    /// binary found in `PATH`
    #[inline]
    pub fn binary(&self) -> &str {
        self.runner_binary.as_str()
    }

    /// Gets the (optional) runner binary arguments
    #[inline]
    pub fn args(&self) -> impl Iterator<Item = &str> {
        self.args.iter().map(AsRef::as_ref)
    }

    /// Returns the location where the platform runner is defined.
    #[inline]
    pub fn source(&self) -> &PlatformRunnerSource {
        &self.source
    }
}

/// The place where a platform runner's configuration was picked up from.
///
/// Returned by [`PlatformRunner::source`].
#[derive(Clone, Debug, PartialEq, Eq)]
pub enum PlatformRunnerSource {
    /// The platform runner was defined by this environment variable.
    Env(String),

    /// The platform runner was defined through a `.cargo/config.toml` or `.cargo/config` file, or
    /// via `--config` (unstable).
    CargoConfig {
        /// The configuration source.
        source: CargoConfigSource,

        /// The table name within `target` that was used.
        ///
        /// # Examples
        ///
        /// If `target.'cfg(target_os = "linux")'.runner` is used, this is `cfg(target_os = "linux")`.
        target_table: String,
    },
}

impl PlatformRunnerSource {
    // https://github.com/rust-lang/cargo/blob/3959f87158ea4f8733e2fcbe032b8a50ae0b6834/src/cargo/util/config/value.rs#L66-L75
    fn resolve_dir<'a>(&'a self, cwd: &'a Utf8Path) -> &'a Utf8Path {
        match self {
            Self::Env(_) => cwd,
            Self::CargoConfig { source, .. } => source.resolve_dir(cwd),
        }
    }
}

impl fmt::Display for PlatformRunnerSource {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        match self {
            Self::Env(var) => {
                write!(f, "environment variable `{var}`")
            }
            Self::CargoConfig {
                source: CargoConfigSource::CliOption,
                target_table,
            } => {
                write!(f, "`target.{target_table}.runner` specified by `--config`")
            }
            Self::CargoConfig {
                source: CargoConfigSource::File(path),
                target_table,
            } => {
                write!(f, "`target.{target_table}.runner` within `{path}`")
            }
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    use camino_tempfile::Utf8TempDir;
    use color_eyre::eyre::{Context, Result};
    use target_spec::TargetFeatures;

    #[test]
    fn test_find_config() {
        let dir = setup_temp_dir().unwrap();
        let dir_path = dir.path().canonicalize_utf8().unwrap();
        let dir_foo_path = dir_path.join("foo");
        let dir_foo_bar_path = dir_foo_path.join("bar");

        // ---
        // Searches through the full directory tree
        // ---
        assert_eq!(
            find_config(
                Platform::new("x86_64-pc-windows-msvc", TargetFeatures::Unknown).unwrap(),
                &[],
                &dir_foo_bar_path,
                &dir_path,
            ),
            Some(PlatformRunner {
                runner_binary: "wine".into(),
                args: vec!["--test-arg".into()],
                source: PlatformRunnerSource::CargoConfig {
                    source: CargoConfigSource::File(dir_path.join("foo/bar/.cargo/config.toml")),
                    target_table: "x86_64-pc-windows-msvc".into()
                },
            }),
        );

        assert_eq!(
            find_config(
                Platform::new("x86_64-pc-windows-gnu", TargetFeatures::Unknown).unwrap(),
                &[],
                &dir_foo_bar_path,
                &dir_path,
            ),
            Some(PlatformRunner {
                runner_binary: "wine2".into(),
                args: vec![],
                source: PlatformRunnerSource::CargoConfig {
                    source: CargoConfigSource::File(dir_path.join("foo/bar/.cargo/config.toml")),
                    target_table: "cfg(windows)".into()
                },
            }),
        );

        assert_eq!(
            find_config(
                Platform::new("x86_64-unknown-linux-gnu", TargetFeatures::Unknown).unwrap(),
                &[],
                &dir_foo_bar_path,
                &dir_path,
            ),
            Some(PlatformRunner {
                runner_binary: dir_path.join("unix-runner"),
                args: vec![],
                source: PlatformRunnerSource::CargoConfig {
                    source: CargoConfigSource::File(dir_path.join(".cargo/config")),
                    target_table: "cfg(unix)".into()
                },
            }),
        );

        // ---
        // Searches starting from the "foo" directory which has no .cargo/config in it
        // ---
        assert_eq!(
            find_config(
                Platform::new("x86_64-pc-windows-msvc", TargetFeatures::Unknown).unwrap(),
                &[],
                &dir_foo_path,
                &dir_path,
            ),
            Some(PlatformRunner {
                runner_binary: dir_path.join("../parent-wine"),
                args: vec![],
                source: PlatformRunnerSource::CargoConfig {
                    source: CargoConfigSource::File(dir_path.join(".cargo/config")),
                    target_table: "x86_64-pc-windows-msvc".into()
                },
            }),
        );

        assert_eq!(
            find_config(
                Platform::new("x86_64-pc-windows-gnu", TargetFeatures::Unknown).unwrap(),
                &[],
                &dir_foo_path,
                &dir_path,
            ),
            None,
        );

        // ---
        // Searches starting and ending at the root directory.
        // ---
        assert_eq!(
            find_config(
                Platform::new("x86_64-pc-windows-msvc", TargetFeatures::Unknown).unwrap(),
                &[],
                &dir_path,
                &dir_path,
            ),
            Some(PlatformRunner {
                runner_binary: dir_path.join("../parent-wine"),
                args: vec![],
                source: PlatformRunnerSource::CargoConfig {
                    source: CargoConfigSource::File(dir_path.join(".cargo/config")),
                    target_table: "x86_64-pc-windows-msvc".into()
                },
            }),
        );

        assert_eq!(
            find_config(
                Platform::new("x86_64-pc-windows-gnu", TargetFeatures::Unknown).unwrap(),
                &[],
                &dir_path,
                &dir_path,
            ),
            None,
        );

        // ---
        // CLI configs
        // ---
        assert_eq!(
            find_config(
                Platform::new("x86_64-pc-windows-msvc", TargetFeatures::Unknown).unwrap(),
                &["target.'cfg(windows)'.runner='windows-runner'"],
                &dir_path,
                &dir_path,
            ),
            Some(PlatformRunner {
                runner_binary: "windows-runner".into(),
                args: vec![],
                source: PlatformRunnerSource::CargoConfig {
                    source: CargoConfigSource::CliOption,
                    target_table: "cfg(windows)".into()
                },
            }),
        );

        assert_eq!(
            find_config(
                Platform::new("x86_64-pc-windows-gnu", TargetFeatures::Unknown).unwrap(),
                &["target.'cfg(windows)'.runner='windows-runner'"],
                &dir_path,
                &dir_path,
            ),
            Some(PlatformRunner {
                runner_binary: "windows-runner".into(),
                args: vec![],
                source: PlatformRunnerSource::CargoConfig {
                    source: CargoConfigSource::CliOption,
                    target_table: "cfg(windows)".into()
                },
            }),
        );

        // cfg(unix) doesn't match this platform.
        assert_eq!(
            find_config(
                Platform::new("x86_64-pc-windows-msvc", TargetFeatures::Unknown).unwrap(),
                &["target.'cfg(unix)'.runner='unix-runner'"],
                &dir_path,
                &dir_path,
            ),
            Some(PlatformRunner {
                runner_binary: dir_path.join("../parent-wine"),
                args: vec![],
                source: PlatformRunnerSource::CargoConfig {
                    source: CargoConfigSource::File(dir_path.join(".cargo/config")),
                    target_table: "x86_64-pc-windows-msvc".into()
                },
            }),
        );

        assert_eq!(
            find_config(
                Platform::new("x86_64-pc-windows-gnu", TargetFeatures::Unknown).unwrap(),
                &["target.'cfg(unix)'.runner='unix-runner'"],
                &dir_path,
                &dir_path,
            ),
            None,
        );

        // Config is followed from left to right.
        assert_eq!(
            find_config(
                Platform::new("x86_64-pc-windows-msvc", TargetFeatures::Unknown).unwrap(),
                &[
                    "target.'cfg(windows)'.runner='windows-runner'",
                    "target.'cfg(all())'.runner='all-runner'"
                ],
                &dir_path,
                &dir_path,
            ),
            Some(PlatformRunner {
                runner_binary: "windows-runner".into(),
                args: vec![],
                source: PlatformRunnerSource::CargoConfig {
                    source: CargoConfigSource::CliOption,
                    target_table: "cfg(windows)".into()
                },
            }),
        );

        assert_eq!(
            find_config(
                Platform::new("x86_64-pc-windows-msvc", TargetFeatures::Unknown).unwrap(),
                &[
                    "target.'cfg(all())'.runner='./all-runner'",
                    "target.'cfg(windows)'.runner='windows-runner'",
                ],
                &dir_path,
                &dir_path,
            ),
            Some(PlatformRunner {
                runner_binary: dir_path.join("all-runner"),
                args: vec![],
                source: PlatformRunnerSource::CargoConfig {
                    source: CargoConfigSource::CliOption,
                    target_table: "cfg(all())".into()
                },
            }),
        );
    }

    fn setup_temp_dir() -> Result<Utf8TempDir> {
        let dir = camino_tempfile::Builder::new()
            .tempdir()
            .wrap_err("error creating tempdir")?;

        std::fs::create_dir_all(dir.path().join(".cargo"))
            .wrap_err("error creating .cargo subdir")?;
        std::fs::create_dir_all(dir.path().join("foo/bar/.cargo"))
            .wrap_err("error creating foo/bar/.cargo subdir")?;

        std::fs::write(dir.path().join(".cargo/config"), CARGO_CONFIG_CONTENTS)
            .wrap_err("error writing .cargo/config")?;
        std::fs::write(
            dir.path().join("foo/bar/.cargo/config.toml"),
            FOO_BAR_CARGO_CONFIG_CONTENTS,
        )
        .wrap_err("error writing foo/bar/.cargo/config.toml")?;

        Ok(dir)
    }

    fn find_config(
        platform: Platform,
        cli_configs: &[&str],
        cwd: &Utf8Path,
        terminate_search_at: &Utf8Path,
    ) -> Option<PlatformRunner> {
        let configs =
            CargoConfigs::new_with_isolation(cli_configs, cwd, terminate_search_at, Vec::new())
                .unwrap();
        PlatformRunner::find_config(&configs, &platform).unwrap()
    }

    static CARGO_CONFIG_CONTENTS: &str = r#"
    [target.x86_64-pc-windows-msvc]
    runner = "../parent-wine"

    [target.'cfg(unix)']
    runner = "./unix-runner"
    "#;

    static FOO_BAR_CARGO_CONFIG_CONTENTS: &str = r#"
    [target.x86_64-pc-windows-msvc]
    runner = ["wine", "--test-arg"]

    [target.'cfg(windows)']
    runner = "wine2"
    "#;
}