use std::path::{Path, PathBuf};

use embed_nu::{Argument, CommandGroupConfig, Context, ValueIntoExpression};
use std::fs;

use crate::{distro::OSConfig, error::ScriptError, utils::CFG_PATH};

#[derive(Clone)]
pub struct ExecBuilder {
    task_config: embed_nu::Value,
    ctx: Context,
}

impl ExecBuilder {
    pub fn create(
        script: PathBuf,
        os_config: OSConfig,
        task_config: embed_nu::Value,
    ) -> Result<Self, ScriptError> {
        let script_contents = Self::get_script_contents(&script)?;

        let mut ctx = Context::builder()
            .with_command_groups(CommandGroupConfig::default().all_groups(true))?
            .add_parent_env_vars()
            .add_var("TRM_CONFIG", os_config)?
            .add_script(script_contents)?
            .build()?;
        if !ctx.has_fn("main") {
            Err(ScriptError::MissingMain(script))
        } else {
            Ok(Self { ctx, task_config })
        }
    }

    #[tracing::instrument(level = "trace", skip_all)]
    pub fn exec(mut self) -> Result<(), ScriptError> {
        let pipeline = self.ctx.call_fn(
            "main",
            vec![Argument::Positional(self.task_config.into_expression())],
        )?;
        self.ctx.print_pipeline_stderr(pipeline)?;

        Ok(())
    }

    /// Returns if the script needs to be run inside the new root
    pub fn requires_chroot(&self) -> bool {
        self.ctx
            .get_var("run_in_chroot")
            .and_then(|v| v.as_bool().ok())
            .unwrap_or(false)
    }

    #[tracing::instrument(level = "trace", skip_all)]
    fn get_script_contents(path: &Path) -> Result<String, ScriptError> {
        let path = CFG_PATH.join(path);

        if path.exists() {
            fs::read_to_string(path).map_err(ScriptError::from)
        } else {
            Err(ScriptError::ScriptNotFound(path))
        }
    }
}