use crate::app_config::AppConfig;
use crate::constants;
use crate::libvirt_lib_structures::XMLUuid;
use crate::utils::files_utils;
use lazy_regex::regex;
use std::os::linux::fs::MetadataExt;
use std::path::{Path, PathBuf};
use std::process::Command;

#[derive(thiserror::Error, Debug)]
enum DisksError {
    #[error("DiskParseError: {0}")]
    Parse(&'static str),
    #[error("DiskConfigError: {0}")]
    Config(&'static str),
    #[error("DiskCreateError")]
    Create,
}

/// Type of disk allocation
#[derive(Copy, Clone, Debug, serde::Serialize, serde::Deserialize)]
pub enum DiskAllocType {
    Fixed,
    Sparse,
}

#[derive(serde::Serialize, serde::Deserialize)]
pub struct Disk {
    /// Disk size, in megabytes
    pub size: usize,
    /// Disk name
    pub name: String,
    pub alloc_type: DiskAllocType,
    /// Set this variable to true to delete the disk
    pub delete: bool,
}

impl Disk {
    pub fn load_from_file(path: &str) -> anyhow::Result<Self> {
        let file = Path::new(path);

        if !file.is_file() {
            return Err(DisksError::Parse("Path is not a file!").into());
        }

        let metadata = file.metadata()?;

        // Approximate estimation
        let is_sparse = metadata.len() / 512 >= metadata.st_blocks();

        Ok(Self {
            size: metadata.len() as usize / (1000 * 1000),
            name: path.rsplit_once('/').unwrap().1.to_string(),
            alloc_type: match is_sparse {
                true => DiskAllocType::Sparse,
                false => DiskAllocType::Fixed,
            },
            delete: false,
        })
    }

    pub fn check_config(&self) -> anyhow::Result<()> {
        if constants::DISK_NAME_MIN_LEN > self.name.len()
            || constants::DISK_NAME_MAX_LEN < self.name.len()
        {
            return Err(DisksError::Config("Disk name length is invalid").into());
        }

        if !regex!("^[a-zA-Z0-9]+$").is_match(&self.name) {
            return Err(DisksError::Config("Disk name contains invalid characters!").into());
        }

        if self.size < constants::DISK_SIZE_MIN || self.size > constants::DISK_SIZE_MAX {
            return Err(DisksError::Config("Disk size is invalid!").into());
        }

        Ok(())
    }

    /// Get disk path
    pub fn disk_path(&self, id: XMLUuid) -> PathBuf {
        let domain_dir = AppConfig::get().vm_storage_path(id);
        domain_dir.join(&self.name)
    }

    /// Apply disk configuration
    pub fn apply_config(&self, id: XMLUuid) -> anyhow::Result<()> {
        self.check_config()?;

        let file = self.disk_path(id);
        files_utils::create_directory_if_missing(file.parent().unwrap())?;

        // Delete file if requested
        if self.delete {
            if !file.exists() {
                log::debug!("File {file:?} does not exists, so it was not deleted");
                return Ok(());
            }

            log::info!("Deleting {file:?}");
            std::fs::remove_file(file)?;
            return Ok(());
        }

        if file.exists() {
            log::debug!("File {file:?} does not exists, so it was not touched");
            return Ok(());
        }

        let mut cmd = Command::new("/usr/bin/dd");
        cmd.arg("if=/dev/zero")
            .arg(format!("of={}", file.to_string_lossy()))
            .arg("bs=1M");

        match self.alloc_type {
            DiskAllocType::Fixed => cmd.arg(format!("count={}", self.size)),
            DiskAllocType::Sparse => cmd.arg(format!("seek={}", self.size)).arg("count=0"),
        };

        let res = cmd.output()?;

        if !res.status.success() {
            log::error!(
                "Failed to create disk! stderr={} stdout={}",
                String::from_utf8_lossy(&res.stderr),
                String::from_utf8_lossy(&res.stdout)
            );
            return Err(DisksError::Create.into());
        }

        Ok(())
    }
}