use crate::config::PlatformConfiguration;
use crate::errors::*;
use crate::project::Project;
use crate::utils::contains_file_with_ext;
use crate::utils::destructure_path;
use crate::utils::file_has_ext;
use crate::utils::lib_name_from;
use crate::Platform;
use dinghy_build::build_env::append_path_to_target_env;
use dinghy_build::build_env::envify;
use dinghy_build::build_env::set_env_ifndef;
use dinghy_build::utils::path_between;
use dirs::home_dir;
use itertools::Itertools;
use std::fs::create_dir_all;
use std::fs::remove_dir_all;
use std::fs::File;
use std::io::Write;
use std::path::Path;
use std::path::PathBuf;
use walkdir::WalkDir;

#[derive(Clone, Debug)]
pub enum OverlayScope {
    Application,
    System,
}

#[derive(Clone, Debug)]
pub struct Overlay {
    pub id: String,
    pub path: PathBuf,
    pub scope: OverlayScope,
}

#[derive(Clone, Debug)]
pub struct Overlayer {
    platform_id: String,
    rustc_triple: Option<String>,
    sysroot: PathBuf,
    work_dir: PathBuf,
}

impl Overlayer {
    pub fn overlay<P: AsRef<Path>>(
        configuration: &PlatformConfiguration,
        platform: &dyn Platform,
        project: &Project,
        sysroot: P,
    ) -> Result<()> {
        let overlayer = Overlayer {
            platform_id: platform.id().to_string(),
            rustc_triple: Some(platform.rustc_triple().to_string()),
            sysroot: sysroot.as_ref().to_path_buf(),
            work_dir: project.overlay_work_dir(platform)?,
        };

        let mut path_to_try = vec![];
        let project_path = project.project_dir()?;
        let mut current_path = project_path.as_path();
        while current_path.parent().is_some() {
            path_to_try.push(
                current_path
                    .join(".dinghy")
                    .join("overlay")
                    .join(&overlayer.platform_id),
            );
            if let Some(parent_path) = current_path.parent() {
                current_path = parent_path;
            } else {
                break;
            }
        }

        // Project may be outside home directory. So add it too.
        if let Some(dinghy_home_dir) = home_dir().map(|it| {
            it.join(".dinghy")
                .join("overlay")
                .join(&overlayer.platform_id)
        }) {
            if !path_to_try.contains(&dinghy_home_dir) {
                path_to_try.push(dinghy_home_dir)
            }
        }

        overlayer.apply_overlay(
            Overlayer::from_conf(configuration)?
                .into_iter()
                .chain(path_to_try.into_iter().flat_map(|path_to_try| {
                    Overlayer::from_directory(path_to_try).unwrap_or_default()
                }))
                .unique_by(|overlay| overlay.id.clone())
                .collect_vec(),
        )
    }

    fn from_conf(configuration: &PlatformConfiguration) -> Result<Vec<Overlay>> {
        Ok(configuration
            .overlays
            .as_ref()
            .unwrap_or(&::std::collections::HashMap::new())
            .into_iter()
            .map(|(overlay_id, overlay_conf)| Overlay {
                id: overlay_id.to_string(),
                path: PathBuf::from(overlay_conf.path.as_str()),
                scope: OverlayScope::Application,
            })
            .collect())
    }

    fn from_directory<P: AsRef<Path>>(overlay_root_dir: P) -> Result<Vec<Overlay>> {
        Ok(overlay_root_dir
            .as_ref()
            .read_dir()
            .with_context(|| {
                format!(
                    "Couldn't read overlay root directory '{}'.",
                    overlay_root_dir.as_ref().display()
                )
            })?
            .filter_map(|it| it.ok()) // Ignore invalid directories
            .map(|it| it.path())
            .filter(|it| it.is_dir())
            .filter_map(destructure_path)
            .map(|(overlay_dir_path, overlay_dir_name)| Overlay {
                id: overlay_dir_name,
                path: overlay_dir_path.to_path_buf(),
                scope: OverlayScope::Application,
            })
            .collect())
    }

    fn apply_overlay<I>(&self, overlays: I) -> Result<()>
    where
        I: IntoIterator<Item = Overlay>,
    {
        let pkg_config_env_var = self
            .rustc_triple
            .as_ref()
            .map(|_| "PKG_CONFIG_LIBDIR")
            // Fallback on PKG_CONFIG_LIBPATH for host as it doesn't erase pkg_config paths
            .unwrap_or("PKG_CONFIG_LIBPATH");

        // Setup overlay work directory
        if let Err(error) = remove_dir_all(&self.work_dir) {
            if self.work_dir.exists() {
                log::warn!(
                    "Couldn't cleanup directory overlay work directory {} ({:?})",
                    self.work_dir.display(),
                    error
                )
            }
        }
        create_dir_all(&self.work_dir).with_context(|| {
            format!(
                "Couldn't create overlay work directory {}.",
                self.work_dir.display()
            )
        })?;
        append_path_to_target_env(
            pkg_config_env_var,
            self.rustc_triple.as_ref(),
            &self.work_dir,
        );

        for overlay in overlays {
            log::debug!("Overlaying '{}'", overlay.id.as_str());
            let mut has_pkg_config_files = false;

            let pkg_config_path_list = WalkDir::new(&overlay.path)
                .into_iter()
                .filter_map(|entry| entry.ok()) // Ignore unreadable directories, maybe could warn...
                .filter(|entry| entry.file_type().is_dir())
                .filter(|dir| {
                    dir.file_name() == "pkgconfig" || contains_file_with_ext(dir.path(), ".pc")
                })
                .map(|pkg_config_path| pkg_config_path.path().to_path_buf());

            for pkg_config_path in pkg_config_path_list {
                log::debug!(
                    "Discovered pkg-config directory '{}'",
                    pkg_config_path.display()
                );
                append_path_to_target_env(
                    pkg_config_env_var,
                    self.rustc_triple.as_ref(),
                    pkg_config_path,
                );
                has_pkg_config_files = true;
            }
            if !has_pkg_config_files {
                self.generate_pkg_config_file(&overlay)?;
                append_path_to_target_env(
                    pkg_config_env_var,
                    self.rustc_triple.as_ref(),
                    &overlay.path,
                );
            }

            // Override the 'prefix' pkg-config variable for the specified overlay only.
            set_env_ifndef(
                envify(format!("PKG_CONFIG_{}_PREFIX", overlay.id)),
                path_between(&self.sysroot, &overlay.path),
            );
        }
        Ok(())
    }

    fn generate_pkg_config_file(&self, overlay: &Overlay) -> Result<()> {
        fn write_pkg_config_file<P: AsRef<Path>, T: AsRef<str>>(
            pc_file_path: P,
            name: &str,
            libs: &[T],
        ) -> Result<()> {
            log::debug!(
                "Generating pkg-config pc file {}",
                pc_file_path.as_ref().display()
            );
            let mut pc_file = File::create(pc_file_path)?;
            pc_file.write_all(b"prefix:/")?;
            pc_file.write_all(b"\nexec_prefix:${prefix}")?;
            pc_file.write_all(b"\nName: ")?;
            pc_file.write_all(name.as_bytes())?;
            pc_file.write_all(b"\nDescription: ")?;
            pc_file.write_all(name.as_bytes())?;
            pc_file.write_all(b"\nVersion: unspecified")?;
            pc_file.write_all(b"\nLibs: -L${prefix} ")?;
            for lib in libs {
                pc_file.write_all(b" -l")?;
                pc_file.write_all(lib.as_ref().as_bytes())?;
            }
            pc_file.write_all(b"\nCflags: -I${prefix}")?;
            Ok(())
        }

        let pc_file = self.work_dir.join(format!("{}.pc", self.platform_id));
        let lib_list = WalkDir::new(&overlay.path)
            .max_depth(1)
            .into_iter()
            .filter_map(|entry| entry.ok()) // Ignore unreadable files, maybe could warn...
            .filter(|entry| file_has_ext(entry.path(), ".so"))
            .filter_map(|e| lib_name_from(e.path()).ok())
            .collect_vec();

        write_pkg_config_file(pc_file.as_path(), overlay.id.as_str(), &lib_list).with_context(
            || {
                format!(
                    "Dinghy couldn't generate pkg-config pc file {}",
                    pc_file.as_path().display()
                )
            },
        )
    }
}