use std::collections::HashMap;
use std::fs::{OpenOptions, read_dir};
use std::io::{Read, Write};
use std::path::{Path, PathBuf};

use fs::expand_files;
use io::run_process;
use java::{JAVA_EXT_CLASS, JAVA_EXT_SOURCE};
use serde::{Deserialize, Serialize};

use crate::Error;
use crate::nest::{F_NEST_LOCK, F_NEST_TOML, Nest, NestLock};
use crate::package::PackageHandler;
use crate::prey::F_PREY_TOML;

pub struct WorkspaceHandler {
    nest: Nest,
    nest_lock: Option<NestLock>,
    project_root: PathBuf,
    packages: HashMap<PathBuf, PackageHandler>,
}

impl WorkspaceHandler {
    const DIR_SRC: &str = "src/";
    const DIR_TARGET: &str = "target/";

    pub fn new<P: AsRef<Path>>(project_root: P) -> crate::Result<Self> {
        let project_root = project_root.as_ref().canonicalize()?;

        Ok(Self {
            nest: Nest::new(
                project_root
                    .file_name()
                    .ok_or(Error::MissingFileName)?
                    .display(),
            ),
            nest_lock: None,
            packages: HashMap::new(),
            project_root,
        })
    }

    pub fn load<P: AsRef<Path>>(project_root: P) -> crate::Result<Self> {
        let project_root = project_root.as_ref().canonicalize()?;

        let mut workspace_manager = Self {
            nest: Nest::try_from(project_root.join(F_NEST_TOML))?,
            nest_lock: NestLock::try_from(project_root.join(F_NEST_LOCK)).ok(),
            packages: HashMap::new(),
            project_root,
        };

        workspace_manager.discover_packages()?;

        Ok(workspace_manager)
    }

    pub fn write(&self) -> crate::Result<()> {
        self.nest.write(self.project_root.join(F_NEST_TOML))?;

        if let Option::Some(lock) = self.nest_lock.clone() {
            lock.write(self.project_root.join(F_NEST_LOCK))?;
        }

        Ok(())
    }

    //pub fn refresh_packages(&mut self) -> crate::Result<()> {}

    /*
    /// Future `build` method.
    pub fn compile(&self, target: Option<PathBuf>) -> crate::Result<()> {
        let mut target = target.unwrap_or(self.nest.default_package());
        if !target.is_file() {
            // Use is_file to skip messing with pathing for src/
            // If target is not a file (explicit entry point), check if it's a known package
            // and use that's package's default entry point.
            target = target.join(
                self.packages
                    .get(&target)
                    .ok_or(Error::UnknownPackage)?
                    .entry_point(),
            );
        }

        //java::Compiler::new();

        Ok(())
    }

    fn make_compiler_job<P: AsRef<Path>>(target: P) {
        // Generate dependency tree.
    }
    */

    pub fn init(&mut self) -> crate::Result<()> {
        let is_empty = read_dir(self.project_root.as_path()).is_ok_and(|tree| tree.count() == 0);

        // ORDER MATTERS. THIS MUST COME FIRST.
        // Make config file.
        self.write_nest()?;

        // Make .java-version
        self.write_java_version()?;

        // Make src/, target/, test/
        self.write_dir_tree()?;

        if !is_empty {
            self.write_example_project()?;
            self.discover_packages()?;

            run_process(&["git", "init", "."])?;
        }

        // Append to .gitignore
        if let Result::Ok(mut f) = OpenOptions::new()
            .append(true)
            .create(true)
            .read(true)
            .open(".gitignore")
        {
            let mut buf = String::new();
            f.read_to_string(&mut buf)?;

            for ignored in [
                "# Automatically added by Raven".to_string(),
                Self::DIR_TARGET.to_string(),
                format!("*.{}", JAVA_EXT_CLASS),
            ] {
                if !buf.contains(&ignored) {
                    f.write(format!("{}\n", ignored).as_bytes())?;
                }
            }
        }

        Ok(())
    }

    // This is the naive build
    pub fn build(&mut self) -> crate::Result<()> {
        let mut targets = vec![];

        for (_name, mut handler) in self.packages.clone() {
            targets.append(&mut handler.get_update_targets()?);
        }

        let compiler = java::compiler::CompilerBuilder::new()
            .class_path(Self::DIR_TARGET)
            .class_path(Self::DIR_TARGET)
            .build();

        for target in targets {
            // Possibly come up with a source file handler for this?
            if let Ok(_) = compiler.clone().compile(target) {
                // No, this does not run O(1)
            }
        }

        Ok(())
    }

    /// Add any newly created packages.
    fn discover_packages(&mut self) -> crate::Result<()> {
        // Scan the src/ directory for entries,
        // filter out the files,
        // then construct PackageManagers for each package

        // Promote *not* using reverse domain name tree structures
        // by improving the speed of package discovery by using read_dir
        // and checking for an immediate Prey.toml before expanding the
        // whole subtree.
        //
        // Yes, I know this looks like shit.
        // That's because it is.

        for file in read_dir(Self::DIR_SRC)?
            // Get directories
            .filter_map(|entry| {
                if entry.as_ref().is_ok_and(|entry| entry.path().is_dir()) {
                    Some(entry.unwrap().path())
                } else {
                    None
                }
            })
            // Get Prey.toml files
            .filter_map(|dir| {
                Some(if dir.join(F_PREY_TOML).exists() {
                    vec![dir.join(F_PREY_TOML)]
                } else {
                    expand_files(dir)
                        .ok()?
                        .iter()
                        .filter_map(|file| {
                            if file.ends_with(PathBuf::from(F_PREY_TOML)) {
                                Some(file.to_owned())
                            } else {
                                None
                            }
                        })
                        .collect()
                })
            })
            .flatten()
        {
            let package_root =
                pathsub::sub_paths(file.as_path(), PathBuf::from(Self::DIR_SRC).as_path()).unwrap();

            self.packages.insert(
                package_root.to_path_buf(),
                PackageHandler::new(package_root, PathBuf::from(Self::DIR_TARGET))?,
            );
        }

        Ok(())
    }

    fn write_nest(&self) -> crate::Result<()> {
        if let Result::Ok(mut f) = OpenOptions::new()
            .write(true)
            .create_new(true)
            .open(F_NEST_TOML)
        {
            f.write_all(toml::to_string_pretty(&self.nest)?.as_bytes())?;
        }

        Ok(())
    }

    fn write_java_version(&self) -> crate::Result<()> {
        if let Result::Ok(mut f) = OpenOptions::new()
            .write(true)
            .create_new(true)
            .open(java::F_JAVA_VERSION)
        {
            f.write_all(format!("{}\n", java::get_javac_ver()?.major.to_string()).as_bytes())?;
        }

        Ok(())
    }

    fn write_dir_tree(&self) -> std::io::Result<()> {
        for dir in [
            format!("{}main/java", Self::DIR_SRC),
            format!("{}test/java", Self::DIR_SRC),
            Self::DIR_TARGET.to_string(),
        ] {
            std::fs::create_dir_all(std::env::current_dir()?.join(dir))?;
        }

        Ok(())
    }

    fn write_example_project(&self) -> std::io::Result<()> {
        // Make src/main/Main.java
        if let Result::Ok(mut f) = OpenOptions::new().write(true).create_new(true).open(
            PathBuf::from(Self::DIR_SRC)
                .join("main/java/Main")
                .with_extension(JAVA_EXT_SOURCE),
        ) {
            f.write_all(include_bytes!("../assets/Main.java"))?;
        }

        // Make src/test/MainTest.java
        if let Result::Ok(mut f) = OpenOptions::new().write(true).create_new(true).open(
            PathBuf::from(Self::DIR_SRC)
                .join("test/java/MainTest")
                .with_extension(JAVA_EXT_SOURCE),
        ) {
            f.write_all(include_bytes!("../assets/MainTest.java"))?;
        }

        Ok(())
    }
}

/// Data struct
#[derive(Debug, Clone, Deserialize, Serialize, Hash, PartialEq, Eq, PartialOrd, Ord)]
pub struct Workspace {
    pub default_package: PathBuf,
}

impl Default for Workspace {
    fn default() -> Self {
        Workspace {
            default_package: PathBuf::from("main"),
        }
    }
}