use std::path::Path;
use std::str::FromStr;

use anyhow::Result;
use tracing::debug;

use platform_host::Platform;
use platform_tags::Tags;
use puffin_client::PypiClientBuilder;
use puffin_interpreter::PythonExecutable;

use crate::commands::ExitStatus;

/// Resolve a set of requirements into a set of pinned versions.
pub(crate) async fn compile(src: &Path, cache: Option<&Path>) -> Result<ExitStatus> {
    // Read the `requirements.txt` from disk.
    let requirements_txt = std::fs::read_to_string(src)?;

    // Parse the `requirements.txt` into a list of requirements.
    let requirements = puffin_package::requirements::Requirements::from_str(&requirements_txt)?;

    // Detect the current Python interpreter.
    let platform = Platform::current()?;
    let python = PythonExecutable::from_env(&platform)?;
    debug!(
        "Using Python interpreter: {}",
        python.executable().display()
    );

    // Determine the current environment markers.
    let markers = python.markers();

    // Determine the compatible platform tags.
    let tags = Tags::from_env(&platform, python.simple_version())?;

    // Instantiate a client.
    let client = {
        let mut pypi_client = PypiClientBuilder::default();
        if let Some(cache) = cache {
            pypi_client = pypi_client.cache(cache);
        }
        pypi_client.build()
    };

    // Resolve the dependencies.
    let resolution = puffin_resolver::resolve(
        &requirements,
        markers,
        &tags,
        &client,
        puffin_resolver::Flags::default(),
    )
    .await?;

    for (name, package) in resolution.iter() {
        #[allow(clippy::print_stdout)]
        {
            println!("{}=={}", name, package.version());
        }
    }

    Ok(ExitStatus::Success)
}