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

use java::{JAVA_EXT_CLASS, JAVA_EXT_SOURCE};
use serde::{Deserialize, Serialize};

use crate::{Error, Result};

/// [`Class`] represents a source file. It is a handler.
#[derive(Debug, Clone, Deserialize, Serialize, Hash, PartialEq, Eq, PartialOrd, Ord)]
pub struct Class {
    /// Path relative to PACKAGE/java, without file extension.
    pub path: PathBuf,
    pub checksum: String,
}

impl Class {
    /// Creates a new [`Class`].
    ///
    /// # Error
    ///
    /// * [`Error::MismatchedPackage`] if the provided `file_path` is absolute, and cannot be
    /// subtracted to just its relative path within its parent package.
    /// * [`Error::Io`] if the source file cannot be loaded and digested.
    pub fn new<P: AsRef<Path>>(package_src_root: P, file_path: P) -> Result<Self> {
        let mut file_path = file_path.as_ref().to_path_buf();
        if file_path.is_absolute() {
            file_path = pathsub::sub_paths(file_path.as_path(), package_src_root.as_ref())
                .ok_or(Error::MismatchedPackage)?;
        }

        Ok(Self {
            path: dbg!(file_path.with_extension("")),
            checksum: sha256::try_digest(package_src_root.as_ref().join(file_path))?,
        })
    }

    /// Returns a boolean representing if the class is up to date.
    ///
    /// # Criteria
    ///
    /// * The class path is local.
    /// * The class has been compiled to `target/`
    /// * The class' source file has not been updated.
    ///
    /// # Errors
    ///
    /// * [`Error::Io`]
    pub fn is_updated<P: AsRef<Path>>(&self, class_path: P) -> Result<bool> {
        // If the path is local and that file has not been updated.
        Ok(class_path
            .as_ref()
            .join(self.path.as_path())
            .with_extension(JAVA_EXT_CLASS)
            .exists()
            && self.checksum == sha256::try_digest(self.path.clone())?)
    }

    /// Updates the class' checksum.
    ///
    /// Only call this if you know that the class has been compiled successfully.
    ///
    /// # Errors
    ///
    /// * [`Error::Io`] if the source file cannot be loaded and digested.
    pub fn update<P: AsRef<Path>>(&mut self, package_src_root: P) -> Result<()> {
        self.checksum = sha256::try_digest(dbg!(
            package_src_root
                .as_ref()
                .join(self.path.as_path())
                .with_extension(JAVA_EXT_SOURCE),
        ))?;
        Ok(())
    }
}