use types::id::ProcessId;

use crate::error::KernelError;

pub struct ProcessMemory {
    process: ProcessId,
    page_count: usize,
    limit: usize,
}

impl ProcessMemory {
    pub fn new(process: ProcessId, limit: usize) -> Self {
        Self {
            process,
            page_count: 0,
            limit,
        }
    }

    pub fn process(&self) -> ProcessId {
        self.process
    }

    pub fn page_count(&self) -> usize {
        self.page_count
    }

    pub fn limit(&self) -> usize {
        self.limit
    }

    pub fn grant(&mut self, count: usize) -> Result<(), KernelError> {
        if self.page_count + count > self.limit {
            return Err(KernelError::OutOfMemory);
        }
        self.page_count += count;
        Ok(())
    }

    pub fn release(&mut self, count: usize) -> Result<(), KernelError> {
        if count > self.page_count {
            return Err(KernelError::OutOfMemory);
        }
        self.page_count -= count;
        Ok(())
    }
}