use crate::error::{ProcessError, Result};
use crate::tools;
use crate::{FILES_TO_CONVERT, FILES_TO_COPY, PATHS_TO_IGNORE};
use log::{debug, info, warn};
use std::collections::HashSet;
use std::fs;
use std::path::{Path, PathBuf};
use std::time::UNIX_EPOCH;

/// DirectoryProcessor handles the conversion of documents from a source directory
/// to a target directory, managing file conversions, copies, and cleanup.
#[derive(Debug)]
pub struct DirectoryProcessor {
    pub(crate) source_dir: PathBuf,
    pub(crate) target_dir: PathBuf,
    pub(crate) source_files: HashSet<PathBuf>,
}

impl DirectoryProcessor {
    /// Creates a new DirectoryProcessor instance.
    ///
    /// # Arguments
    /// * `source` - The source directory containing files to process
    /// * `target` - The target directory where processed files will be placed
    pub fn new(source: PathBuf, target: PathBuf) -> Self {
        Self {
            source_dir: source,
            target_dir: target,
            source_files: HashSet::new(),
        }
    }

    /// Determines if a file needs to be copied or converted based on modification times.
    pub(crate) fn needs_copy_or_conversion(source_path: &Path, dest_path: &Path) -> bool {
        if !dest_path.exists() {
            return true;
        }

        let source_modified = fs::metadata(source_path)
            .and_then(|m| m.modified())
            .unwrap_or(UNIX_EPOCH);

        let dest_modified = fs::metadata(dest_path)
            .and_then(|m| m.modified())
            .unwrap_or(UNIX_EPOCH);

        source_modified > dest_modified
    }

    /// Collects all source files that need processing.
    fn get_source_files(&mut self, current_dir: &Path) -> Result<()> {
        let entries = fs::read_dir(current_dir).map_err(ProcessError::Io)?;

        for entry in entries.flatten() {
            let path = entry.path();
            if path.is_dir() {
                self.get_source_files(&path)?;
            } else if let Some(ext) = path.extension().and_then(|e| e.to_str()) {
                let ext = ext.to_lowercase();
                if FILES_TO_CONVERT.contains(&ext.as_str()) || FILES_TO_COPY.contains(&ext.as_str()) {
                    if let Ok(rel_path) = path.strip_prefix(&self.source_dir) {
                        self.source_files.insert(rel_path.to_path_buf());
                    }
                }
            }
        }
        Ok(())
    }

    /// Cleans up the target directory by removing obsolete files and empty directories.
    fn clean_target_directory(&self, current_dir: &Path) -> Result<bool> {
        let entries = fs::read_dir(current_dir).map_err(ProcessError::Io)?;
        let mut is_empty = true;

        for entry in entries.flatten() {
            let path = entry.path();
            
            // Check if path should be ignored
            if let Some(name) = path.file_name().and_then(|n| n.to_str()) {
                if PATHS_TO_IGNORE.iter().any(|&ignore| name.contains(ignore)) {
                    is_empty = false;
                    continue;
                }
            }

            if path.is_dir() {
                match self.clean_target_directory(&path) {
                    Ok(subdir_empty) => {
                        if subdir_empty {
                            if let Err(e) = fs::remove_dir(&path) {
                                warn!("Could not remove empty directory {}: {}", path.display(), e);
                            } else {
                                debug!("Removed empty directory: {}", path.display());
                            }
                        } else {
                            is_empty = false;
                        }
                    }
                    Err(e) => {
                        warn!("Error cleaning directory {}: {}", path.display(), e);
                        is_empty = false;
                    }
                }
            } else {
                let rel_path = path.strip_prefix(&self.target_dir).map_err(ProcessError::StripPrefix)?;
                let should_exist = self.should_file_exist(rel_path);

                if !should_exist {
                    if let Err(e) = fs::remove_file(&path) {
                        warn!("Could not remove file {}: {}", path.display(), e);
                    } else {
                        debug!("Removed obsolete file: {}", path.display());
                    }
                } else {
                    is_empty = false;
                }
            }
        }

        Ok(is_empty)
    }

    /// Determines if a file in the target directory should exist based on source files.
    fn should_file_exist(&self, rel_path: &Path) -> bool {
        if let Some(ext) = rel_path.extension().and_then(|e| e.to_str()) {
            if ext == "pdf" {
                // For PDF files, check if any corresponding source file exists
                FILES_TO_CONVERT
                    .iter()
                    .any(|&ext| self.source_files.contains(&rel_path.with_extension(ext)))
            } else {
                // For other files, check if they exist in source
                self.source_files.contains(rel_path)
            }
        } else {
            false
        }
    }

    /// Processes a single directory, converting or copying files as needed.
    fn process_directory(&self, current_source: &Path, current_target: &Path) -> Result<()> {
        fs::create_dir_all(current_target).map_err(ProcessError::Io)?;

        let entries = fs::read_dir(current_source).map_err(ProcessError::Io)?;

        for entry in entries.flatten() {
            let path = entry.path();

            if path.is_dir() {
                let relative_path = path
                    .strip_prefix(&self.source_dir)
                    .map_err(ProcessError::StripPrefix)?;
                let dest_subdir = self.target_dir.join(relative_path);
                self.process_directory(&path, &dest_subdir)?;
            } else {
                self.process_file(&path, current_source, current_target)?;
            }
        }
        Ok(())
    }

    /// Processes a single file, either converting it to PDF or copying it.
    fn process_file(&self, path: &Path, current_source: &Path, current_target: &Path) -> Result<()> {
        if let Some(ext) = path.extension().and_then(|e| e.to_str()) {
            let relative_path = path
                .strip_prefix(current_source)
                .map_err(ProcessError::StripPrefix)?;

            let ext = ext.to_lowercase();
            if FILES_TO_CONVERT.contains(&ext.as_str()) {
                self.convert_file(path, relative_path, current_target)?;
            } else if FILES_TO_COPY.contains(&ext.as_str()) {
                self.copy_file(path, relative_path, current_target)?;
            }
        }
        Ok(())
    }

    /// Converts a file to PDF format.
    fn convert_file(&self, path: &Path, relative_path: &Path, current_target: &Path) -> Result<()> {
        let pdf_path = current_target.join(relative_path.with_extension("pdf"));
        
        if Self::needs_copy_or_conversion(path, &pdf_path) {
            tools::convert_file(path, pdf_path.parent().unwrap_or(current_target))
                .map_err(|e| ProcessError::Processing(e))?;
            
            info!(
                "Converted: {} -> {}",
                path.strip_prefix(&self.source_dir).unwrap().display(),
                pdf_path.strip_prefix(&self.target_dir).unwrap().display()
            );
        }
        Ok(())
    }

    /// Copies a file to the target directory.
    fn copy_file(&self, path: &Path, relative_path: &Path, current_target: &Path) -> Result<()> {
        let dest_path = current_target.join(relative_path);
        if Self::needs_copy_or_conversion(path, &dest_path) {
            fs::copy(path, &dest_path).map_err(ProcessError::Io)?;
            info!(
                "Copied file: {} -> {}",
                path.strip_prefix(&self.source_dir).unwrap().display(),
                dest_path.strip_prefix(&self.target_dir).unwrap().display()
            );
        }
        Ok(())
    }

    /// Processes all files in the source directory, converting or copying them as needed,
    /// and then cleans up the target directory.
    pub fn process(&mut self) -> Result<()> {
        debug!("Collecting source files");
        self.get_source_files(&self.source_dir.to_owned())?;
        
        debug!("Starting directory processing");
        self.process_directory(&self.source_dir.to_owned(), &self.target_dir.to_owned())?;
        
        debug!("Cleaning target directory");
        self.clean_target_directory(&self.target_dir.to_owned())?;
        
        info!("Directory processing completed successfully");
        Ok(())
    }
}