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// Conserve backup system.
// Copyright 2017-2023 Martin Pool.

// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

//! Abstract Tree trait.

use std::sync::Arc;

use crate::counters::Counter;
use crate::monitor::Monitor;
use crate::*;

/// Abstract Tree that may be either on the real filesystem or stored in an archive.
pub trait ReadTree {
    type Entry: EntryTrait + 'static;
    type IT: Iterator<Item = Self::Entry>;

    /// Iterate, in apath order, all the entries in this tree.
    ///
    /// Errors reading individual paths or directories are sent to the UI and
    /// counted, but are not treated as fatal, and don't appear as Results in the
    /// iterator.
    fn iter_entries(&self, subtree: Apath, exclude: Exclude) -> Result<Self::IT>;

    /// Measure the tree size.
    ///
    /// This typically requires walking all entries, which may take a while.
    fn size(&self, exclude: Exclude, monitor: Arc<dyn Monitor>) -> Result<TreeSize> {
        let mut file_bytes = 0u64;
        let task = monitor.start_task("Measure tree".to_string());
        for e in self.iter_entries(Apath::root(), exclude)? {
            // While just measuring size, ignore directories/files we can't stat.
            if let Some(bytes) = e.size() {
                monitor.count(Counter::Files, 1);
                monitor.count(Counter::FileBytes, bytes as usize);
                file_bytes += bytes;
                task.increment(bytes as usize);
            }
        }
        Ok(TreeSize { file_bytes })
    }
}

/// The measured size of a tree.
pub struct TreeSize {
    pub file_bytes: u64,
}