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

#[derive(Debug, PartialEq)]
pub enum ProjectType {
    Maven,
    Npm,
    Cargo
}

impl ProjectType {
    fn detect<P: AsRef<Path>>(path: P) -> Option<ProjectType> {
        let project_path: PathBuf = path.as_ref().into();
        if project_path.join("pom.xml").is_file() {
            return Some(ProjectType::Maven);
        } else if project_path.join("package.json").is_file() {
            return Some(ProjectType::Npm);
        } else if project_path.join("Cargo.toml").is_file() {
            return Some(ProjectType::Cargo);
        }
        
        None
    }
    
    pub fn build_command(&self) -> Vec<String> {
        match self {
            ProjectType::Maven => vec!["mvn".to_owned(), "install".to_owned()],
            ProjectType::Npm => vec!["npm".to_owned(), "build".to_owned()],
            ProjectType::Cargo => vec!["cargo".to_owned(), "build".to_owned()]
        }
    }
    
    pub fn run_command(&self) -> Vec<String> {
        match self {
            ProjectType::Maven => vec!["mvn".to_owned(), "exec".to_owned()],
            ProjectType::Npm => vec!["npm".to_owned(), "start".to_owned()],
            ProjectType::Cargo => vec!["cargo".to_owned(), "run".to_owned()]
        }
    }
}

#[derive(Debug)]
pub struct Project {
    pub project_type: ProjectType,
    path: PathBuf
}

impl Project {
    pub fn path(&self) -> &Path {
        &self.path
    }
    
    pub fn info(&self) -> ProjectInfo {
        match self.project_type {
            ProjectType::Maven => {
                let effective_pom = self.read_effective_pom();
                ProjectInfo::from_pom(&effective_pom)
            },
            ProjectType::Npm => ProjectInfo {
                name: "placeholder".into(),
                version: "placeholder".into()
            },
            ProjectType::Cargo => self.read_cargo_metadata().into()
        }
    }
    
    fn read_cargo_metadata(&self) -> cargo_metadata::Metadata {
        cargo_metadata::MetadataCommand::new()
            .current_dir(&self.path)
            .exec()
            .expect("metadata call failed")
    }
    
    fn read_effective_pom(&self) -> sxd_document::Package {
        let full_output = std::str::from_utf8(&Command::new("mvn")
            .arg("help:effective-pom")
            .current_dir(&self.path)
            .output()
            .expect("failed to generate effective pom")
            .stdout).expect("failed to generate string from output").to_owned();
        let xml = full_output.get(
            full_output.find("<?xml").expect("failed to find start of xml")
            ..
            full_output.find("</project>").expect("failed to find end of xml") + 10
        ).expect("failed to extract xml body");
        sxd_document::parser::parse(xml).expect("failed to parse effective pom")
    }
}

#[derive(Debug)]
pub struct ProjectInfo {
    pub name: String,
    pub version: String
}

impl From<cargo_metadata::Metadata> for ProjectInfo {
    fn from(metadata: cargo_metadata::Metadata) -> Self {
        let root_package_id = metadata.resolve
            .expect("non-existent resolve field")
            .root
            .expect("non-existent root package id");
        let package = metadata.packages.into_iter()
            .find(|package| package.id == root_package_id)
            .expect("failed to find package in metadata");
        ProjectInfo {
            name: package.name.into(),
            version: format!("{}", package.version)
        }     
    }
}

impl ProjectInfo {
    fn from_pom(pom: &sxd_document::Package) -> Self {
        let document = pom.as_document();
        
        let mut context = sxd_xpath::context::Context::new();
        context.set_namespace("mvn", "http://maven.apache.org/POM/4.0.0");
        
        let factory = sxd_xpath::Factory::new();
        let name_xpath = factory.build("/mvn:project/mvn:name")
            .expect("failed to compile name xpath")
            .expect("No XPath was compiled");
        let version_xpath = factory.build("/mvn:project/mvn:version")
            .expect("failed to compile name xpath")
            .expect("No XPath was compiled");
        
        ProjectInfo {
            name: name_xpath.evaluate(&context, document.root())
                .expect("failed to evaluate name expression")
                .into_string(),
            version: version_xpath.evaluate(&context, document.root())
                .expect("failed to evaluate version expression")
                .into_string(),
        }        
    }
}

pub struct Scouter {
    search_path: PathBuf
}

impl Scouter {
    pub fn new<P: AsRef<Path>>(path: P) -> Scouter {
        let mut search_path: PathBuf = path.as_ref().into();
        if !search_path.is_dir() {
            search_path.pop();
        }
        
        Scouter {
            search_path: search_path
        }
    }
}

impl Iterator for Scouter {
    type Item = Project;
    
    fn next(&mut self) -> Option<Self::Item> {
        loop {
            let project_type = ProjectType::detect(&self.search_path);
            if project_type.is_some()
            {
                return project_type.map(|project_type| Project {
                    project_type: project_type,
                    path: self.search_path.to_owned()
                });
            }
            
            if !self.search_path.pop()
            {
                return None;
            }
        }
    }
}

#[cfg(test)]
mod test {
    use super::{ProjectType, Scouter};
    
    #[test]
    fn test_scouter() {
        let mut scouter = Scouter::new(file!());
        let project = scouter.next().unwrap();
        let project_info = project.info();
        assert_eq!(ProjectType::Cargo, project.project_type);
        assert_eq!(env!("CARGO_PKG_NAME"), project_info.name);
        assert_eq!(env!("CARGO_PKG_VERSION"), project_info.version);
    }
    
    #[test]
    fn test_maven_project() {
        let mut scouter = Scouter::new(format!("{}/testdata/maven", env!("CARGO_MANIFEST_DIR")));
        let project = scouter.next().unwrap();
        let project_info = project.info();
        assert_eq!(ProjectType::Maven, project.project_type);
        assert_eq!("Shenlong Maven Test Project", project_info.name);
        assert_eq!("1.0.0-SNAPSHOT", project_info.version);
    }
}