loadsmith-install 0.3.1

use std::{
    fmt::Debug,
    fs::{self},
    path::Path,
};

use camino::Utf8PathBuf;
use loadsmith_core::{Checksum, InstalledFile, InstalledPackage, PackageRef};
use tracing::{debug, trace};
use walkdir::WalkDir;

use crate::{
    InstallRule, InstallRuleset,
    error::{Error, Result},
};

/// Install a package's files into a game profile directory.
///
/// Walks `source` recursively, maps each file through the given `ruleset`, and
/// copies (or hard-links) the mapped files into `profile`. Returns the
/// [`InstalledPackage`](loadsmith_core::InstalledPackage) descriptor and a list
/// of file paths that were overwritten.
///
/// # Examples
///
/// ```rust,no_run
/// use camino::Utf8Path;
/// use loadsmith_core::{PackageRef, Version, PackageId};
/// use loadsmith_install::{install, InstallRuleset, InstallRule, GlobRule};
///
/// let pkg = PackageRef::new(PackageId::new("denikson-BepInExPack_Valheim"), Version::new(5, 4, 22));
/// let rule = InstallRule::Glob(
///     GlobRule::try_from_pattern("**", Utf8Path::new("BepInEx")).unwrap()
/// );
/// let rules = [rule];
/// let ruleset = InstallRuleset::new(&rules);
/// let (installed, overwritten) = install(
///     pkg,
///     ruleset,
///     "C:\\extracted\\package",
///     "C:\\games\\Valheim\\profile",
///     false,
///     None,
/// ).unwrap();
/// ```
pub fn install(
    package: PackageRef,
    ruleset: InstallRuleset,
    source: impl AsRef<Path>,
    profile: impl AsRef<Path>,
    no_links: bool,
    checksum: Option<Checksum>,
) -> Result<(InstalledPackage, Vec<Utf8PathBuf>)> {
    let source = source.as_ref();
    let profile = profile.as_ref();

    let mut installed_files = Vec::new();
    let mut overriden_files = Vec::new();

    let walkdir = WalkDir::new(source).follow_links(false).into_iter();

    for entry in walkdir {
        let entry = entry?;

        if entry.file_type().is_dir() {
            continue; // we create the necessary dirs when creating files instead
        }

        let relative_path = entry
            .path()
            .strip_prefix(source)
            .expect("entry path should be relative to source");

        let relative_path = Utf8PathBuf::try_from(relative_path.to_path_buf())?;

        let Some((mapped, rule)) = ruleset.map_file_and_return_rule(&relative_path, &package)
        else {
            debug!(%relative_path, "files left unmapped by ruleset, skipping");
            continue;
        };

        trace!(
            from = ?relative_path,
            to = ?mapped,
            "mapped file"
        );

        let (installed, overwrote) =
            install_file(entry.path(), &profile.join(&mapped), mapped, rule, no_links)?;

        if let Some(installed) = installed {
            installed_files.push(installed);
        }

        if overwrote {
            overriden_files.push(relative_path);
        }
    }

    Ok((
        InstalledPackage::now(package, installed_files, checksum),
        overriden_files,
    ))
}

fn install_file(
    source: &Path,
    target: &Path,
    mapped_relative: Utf8PathBuf,
    rule: &InstallRule,
    no_links: bool,
) -> Result<(Option<InstalledFile>, bool)> {
    let link = !no_links && rule.use_links();
    let mut overwrote = false;

    if target.exists() {
        match rule.conflict_strategy() {
            ConflictStrategy::Overwrite => {
                trace!(%mapped_relative, "overwriting existing file");
                overwrote = true;
                // fs::copy already overwrites the file, no need to remove it first
                if link {
                    fs::remove_file(&target)?;
                }
            }
            ConflictStrategy::Skip => {
                trace!(%mapped_relative, "skipping existing file");
                return Ok((None, false));
            }
            ConflictStrategy::Error => {
                return Err(Error::FileAlreadyExists(target.into()));
            }
        }
    }

    loadsmith_util::create_parent_dirs(&target)?;

    if link {
        trace!(%mapped_relative, "link file");
        fs::hard_link(source, &target)?;
    } else {
        trace!(%mapped_relative, "copy file");
        fs::copy(source, &target)?;
    }

    Ok((Some(InstalledFile::new(mapped_relative, link)), overwrote))
}

/// Strategy for handling file conflicts during installation.
///
/// # Examples
///
/// ```rust
/// use loadsmith_install::ConflictStrategy;
///
/// let strategy = ConflictStrategy::Overwrite;
/// assert_eq!(strategy, ConflictStrategy::Overwrite);
/// ```
#[derive(Debug, Clone, Copy, PartialEq, Eq)]
pub enum ConflictStrategy {
    /// Overwrite the existing file.
    Overwrite,
    /// Skip the existing file and keep the original.
    Skip,
    /// Return a [`FileAlreadyExists`](crate::Error::FileAlreadyExists) error.
    Error,
}