use super::DapLocator;
use anyhow::{Result, anyhow};
use async_trait::async_trait;
use serde_json::Value;
use smol::{
    io::AsyncReadExt,
    process::{Command, Stdio},
};
use task::DebugTaskDefinition;

pub(crate) struct CargoLocator;

async fn find_best_executable(executables: &[String], test_name: &str) -> Option<String> {
    if executables.len() == 1 {
        return executables.first().cloned();
    }
    for executable in executables {
        let Some(mut child) = Command::new(&executable)
            .arg("--list")
            .stdout(Stdio::piped())
            .spawn()
            .ok()
        else {
            continue;
        };
        let mut test_lines = String::default();
        if let Some(mut stdout) = child.stdout.take() {
            stdout.read_to_string(&mut test_lines).await.ok();
            for line in test_lines.lines() {
                if line.contains(&test_name) {
                    return Some(executable.clone());
                }
            }
        }
    }
    None
}
#[async_trait]
impl DapLocator for CargoLocator {
    async fn run_locator(
        &self,
        mut debug_config: DebugTaskDefinition,
    ) -> Result<DebugTaskDefinition> {
        let Some(launch_config) = (match &mut debug_config.request {
            task::DebugRequest::Launch(launch_config) => Some(launch_config),
            _ => None,
        }) else {
            return Err(anyhow!("Couldn't get launch config in locator"));
        };

        let Some(cwd) = launch_config.cwd.clone() else {
            return Err(anyhow!(
                "Couldn't get cwd from debug config which is needed for locators"
            ));
        };

        let mut child = Command::new("cargo")
            .args(&launch_config.args)
            .arg("--message-format=json")
            .current_dir(cwd)
            .stdout(Stdio::piped())
            .spawn()?;

        let mut output = String::new();
        if let Some(mut stdout) = child.stdout.take() {
            stdout.read_to_string(&mut output).await?;
        }

        let status = child.status().await?;
        if !status.success() {
            return Err(anyhow::anyhow!("Cargo command failed"));
        }

        let executables = output
            .lines()
            .filter(|line| !line.trim().is_empty())
            .filter_map(|line| serde_json::from_str(line).ok())
            .filter_map(|json: Value| {
                json.get("executable")
                    .and_then(Value::as_str)
                    .map(String::from)
            })
            .collect::<Vec<_>>();
        if executables.is_empty() {
            return Err(anyhow!("Couldn't get executable in cargo locator"));
        };

        let is_test = launch_config
            .args
            .first()
            .map_or(false, |arg| arg == "test");

        let mut test_name = None;
        if is_test {
            if let Some(package_index) = launch_config
                .args
                .iter()
                .position(|arg| arg == "-p" || arg == "--package")
            {
                test_name = launch_config
                    .args
                    .get(package_index + 2)
                    .filter(|name| !name.starts_with("--"))
                    .cloned();
            }
        }
        let executable = {
            if let Some(ref name) = test_name {
                find_best_executable(&executables, &name).await
            } else {
                None
            }
        };

        let Some(executable) = executable.or_else(|| executables.first().cloned()) else {
            return Err(anyhow!("Couldn't get executable in cargo locator"));
        };

        launch_config.program = executable;

        launch_config.args.clear();
        if let Some(test_name) = test_name {
            launch_config.args.push(test_name);
        }
        Ok(debug_config)
    }
}