use serde::Serialize;
use std::{fmt::Write as _, path::Path};

#[derive(Debug, Serialize, Clone, PartialEq, Eq)]
pub struct AppProject {
    pub name: String,
    pub route_path: String,
}

impl AppProject {
    pub fn initial(&self) -> String {
        self.name
            .chars()
            .next()
            .unwrap_or('A')
            .to_uppercase()
            .to_string()
    }
}

pub fn scan_projects(root: &Path) -> Vec<AppProject> {
    let mut projects = Vec::new();

    let Ok(read_dir) = std::fs::read_dir(root) else {
        return projects;
    };

    for item in read_dir.flatten() {
        let path = item.path();
        let name = item.file_name().to_string_lossy().to_string();

        if name.starts_with('.') {
            continue;
        }

        if path.is_dir() {
            let has_index = path.join("index.html").exists() || path.join("index.htm").exists();
            if has_index {
                let route_path = format!("/{}/", encode_path_segment(&name));
                projects.push(AppProject { name, route_path });
            }
        }
    }

    projects.sort_by(|a, b| {
        a.name
            .to_lowercase()
            .cmp(&b.name.to_lowercase())
            .then_with(|| a.name.cmp(&b.name))
    });
    projects
}

fn encode_path_segment(segment: &str) -> String {
    let mut encoded = String::with_capacity(segment.len());

    for byte in segment.bytes() {
        if byte.is_ascii_alphanumeric() || matches!(byte, b'-' | b'_' | b'.' | b'~') {
            encoded.push(char::from(byte));
        } else {
            write!(&mut encoded, "%{byte:02X}").expect("写入字符串不会失败");
        }
    }

    encoded
}

#[cfg(test)]
mod tests {
    use super::*;
    use std::{
        fs,
        path::PathBuf,
        sync::atomic::{AtomicU64, Ordering},
    };

    static NEXT_TEMP_ID: AtomicU64 = AtomicU64::new(0);

    struct TestDir {
        path: PathBuf,
    }

    impl TestDir {
        fn new() -> Self {
            let id = NEXT_TEMP_ID.fetch_add(1, Ordering::Relaxed);
            let path =
                std::env::temp_dir().join(format!("stash-core-test-{}-{id}", std::process::id()));
            fs::create_dir_all(&path).expect("应能创建测试目录");
            Self { path }
        }

        fn path(&self) -> &Path {
            &self.path
        }

        fn add_project(&self, name: &str, index_file: &str) {
            let project = self.path.join(name);
            fs::create_dir_all(&project).expect("应能创建项目目录");
            fs::write(project.join(index_file), "<!doctype html>").expect("应能创建入口文件");
        }
    }

    impl Drop for TestDir {
        fn drop(&mut self) {
            let _ = fs::remove_dir_all(&self.path);
        }
    }

    #[test]
    fn scan_projects_detects_only_immediate_visible_projects() {
        let root = TestDir::new();
        root.add_project("with-html", "index.html");
        root.add_project("with-htm", "index.htm");
        root.add_project(".hidden", "index.html");
        root.add_project("no-index", "readme.txt");
        root.add_project("parent/child", "index.html");
        fs::create_dir_all(root.path().join("plain-directory")).expect("应能创建普通目录");

        let names: Vec<_> = scan_projects(root.path())
            .into_iter()
            .map(|project| project.name)
            .collect();

        assert_eq!(names, vec!["with-htm", "with-html"]);
    }

    #[test]
    fn scan_projects_sorts_names_case_insensitively() {
        let root = TestDir::new();
        root.add_project("zeta", "index.html");
        root.add_project("ALPHA", "index.html");
        root.add_project("middle", "index.html");

        let names: Vec<_> = scan_projects(root.path())
            .into_iter()
            .map(|project| project.name)
            .collect();

        assert_eq!(names, vec!["ALPHA", "middle", "zeta"]);
    }

    #[test]
    fn scan_projects_url_encodes_route_segments() {
        let root = TestDir::new();
        root.add_project("space name", "index.html");
        root.add_project("中文", "index.html");

        let projects = scan_projects(root.path());

        assert_eq!(projects[0].name, "space name");
        assert_eq!(projects[0].route_path, "/space%20name/");
        assert_eq!(projects[1].name, "中文");
        assert_eq!(projects[1].route_path, "/%E4%B8%AD%E6%96%87/");
    }

    #[test]
    fn path_segment_encoding_preserves_unreserved_characters() {
        assert_eq!(encode_path_segment("aZ09-_.~/?#%"), "aZ09-_.~%2F%3F%23%25");
    }
}