use std::collections::HashMap;
use std::path::Path;
use std::sync::LazyLock;

use crate::models::{FileCategory, OrganizationPlan};

static EXTENSION_MAP: LazyLock<HashMap<&'static str, &'static str>> = LazyLock::new(|| {
    HashMap::from([
        // Images
        ("jpg", "Images"),
        ("jpeg", "Images"),
        ("png", "Images"),
        ("gif", "Images"),
        ("bmp", "Images"),
        ("svg", "Images"),
        ("webp", "Images"),
        ("ico", "Images"),
        ("tiff", "Images"),
        ("tif", "Images"),
        ("raw", "Images"),
        ("heic", "Images"),
        ("heif", "Images"),
        // Documents
        ("pdf", "Documents"),
        ("doc", "Documents"),
        ("docx", "Documents"),
        ("txt", "Documents"),
        ("rtf", "Documents"),
        ("odt", "Documents"),
        ("xls", "Documents"),
        ("xlsx", "Documents"),
        ("ppt", "Documents"),
        ("pptx", "Documents"),
        ("csv", "Documents"),
        ("md", "Documents"),
        ("epub", "Documents"),
        // Installers
        ("exe", "Installers"),
        ("msi", "Installers"),
        ("dmg", "Installers"),
        ("deb", "Installers"),
        ("rpm", "Installers"),
        ("app", "Installers"),
        ("appimage", "Installers"),
        ("pkg", "Installers"),
        ("snap", "Installers"),
        // Music
        ("mp3", "Music"),
        ("wav", "Music"),
        ("flac", "Music"),
        ("aac", "Music"),
        ("ogg", "Music"),
        ("wma", "Music"),
        ("m4a", "Music"),
        ("opus", "Music"),
        ("aiff", "Music"),
        // Video
        ("mp4", "Video"),
        ("mkv", "Video"),
        ("avi", "Video"),
        ("mov", "Video"),
        ("wmv", "Video"),
        ("flv", "Video"),
        ("webm", "Video"),
        ("m4v", "Video"),
        ("mpeg", "Video"),
        ("mpg", "Video"),
        // Archives
        ("zip", "Archives"),
        ("tar", "Archives"),
        ("gz", "Archives"),
        ("rar", "Archives"),
        ("7z", "Archives"),
        ("bz2", "Archives"),
        ("xz", "Archives"),
        ("tgz", "Archives"),
        ("zst", "Archives"),
        // Code
        ("rs", "Code"),
        ("py", "Code"),
        ("js", "Code"),
        ("ts", "Code"),
        ("java", "Code"),
        ("c", "Code"),
        ("cpp", "Code"),
        ("h", "Code"),
        ("hpp", "Code"),
        ("go", "Code"),
        ("rb", "Code"),
        ("php", "Code"),
        ("html", "Code"),
        ("css", "Code"),
        ("json", "Code"),
        ("yaml", "Code"),
        ("yml", "Code"),
        ("toml", "Code"),
        ("xml", "Code"),
        ("sh", "Code"),
        ("bash", "Code"),
        ("sql", "Code"),
    ])
});

/// Categorizes a file by its extension.
/// Returns `Some(category)` if the extension is known, `None` otherwise.
pub fn categorize_by_extension(filename: &str) -> Option<&'static str> {
    Path::new(filename)
        .extension()
        .and_then(|ext| ext.to_str())
        .map(|ext| ext.to_lowercase())
        .as_deref()
        .and_then(|ext| EXTENSION_MAP.get(ext).copied())
}

/// Result of offline categorization
pub struct OfflineCategorizationResult {
    pub plan: OrganizationPlan,
    pub skipped: Vec<String>,
}

/// Categorizes a list of filenames using extension-based rules.
/// Returns categorized files and a list of skipped filenames.
pub fn categorize_files_offline(filenames: Vec<String>) -> OfflineCategorizationResult {
    let mut files = Vec::with_capacity(filenames.len());
    let mut skipped = Vec::new();

    for filename in filenames {
        match categorize_by_extension(&filename) {
            Some(category) => {
                files.push(FileCategory {
                    filename,
                    category: category.to_string(),
                    sub_category: String::new(),
                });
            }
            None => {
                skipped.push(filename);
            }
        }
    }

    OfflineCategorizationResult {
        plan: OrganizationPlan { files },
        skipped,
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_categorize_known_extensions() {
        assert_eq!(categorize_by_extension("photo.jpg"), Some("Images"));
        assert_eq!(categorize_by_extension("document.pdf"), Some("Documents"));
        assert_eq!(categorize_by_extension("setup.exe"), Some("Installers"));
        assert_eq!(categorize_by_extension("song.mp3"), Some("Music"));
        assert_eq!(categorize_by_extension("movie.mp4"), Some("Video"));
        assert_eq!(categorize_by_extension("archive.zip"), Some("Archives"));
        assert_eq!(categorize_by_extension("main.rs"), Some("Code"));
    }

    #[test]
    fn test_categorize_case_insensitive() {
        assert_eq!(categorize_by_extension("PHOTO.JPG"), Some("Images"));
        assert_eq!(categorize_by_extension("Photo.Png"), Some("Images"));
    }

    #[test]
    fn test_categorize_unknown_extension() {
        assert_eq!(categorize_by_extension("file.xyz"), None);
        assert_eq!(categorize_by_extension("file.unknown"), None);
    }

    #[test]
    fn test_categorize_no_extension() {
        assert_eq!(categorize_by_extension("README"), None);
        assert_eq!(categorize_by_extension("Makefile"), None);
    }

    #[test]
    fn test_categorize_files_offline() {
        let filenames = vec![
            "photo.jpg".to_string(),
            "doc.pdf".to_string(),
            "unknown".to_string(),
            "file.xyz".to_string(),
        ];

        let result = categorize_files_offline(filenames);

        assert_eq!(result.plan.files.len(), 2);
        assert_eq!(result.skipped.len(), 2);
        assert!(result.skipped.contains(&"unknown".to_string()));
        assert!(result.skipped.contains(&"file.xyz".to_string()));
    }
}