using Invercargill;
using Invercargill.DataStructures;

/**
 * `usm remove [-y|--yes] <packages>` — remove installed packages and,
 * by cascade, every installed package that transitively depends on any
 * of them (discovered through {@link Usm.SystemState.find_dependant_names},
 * so the summary shows the full closure before anything happens). All
 * requested cascades merge into one plan and one confirm.
 *
 * The plan then gains every orphaned dependency: a remaining package
 * installed implicitly ({@link Usm.OriginInformation.explicitly_installed}
 * false — a resolved dependency, or a record from before the field
 * existed) that no package surviving the removal depends on. Orphans
 * appear under their own "remove (orphaned)" label in the summary, and
 * nothing is removed without confirmation.
 *
 * After the transaction each removed package's state directory —
 * sources, build cache, `installed/` entry — is deleted; OTHER versions'
 * directories (the siblings updates keep for downgrade) remain.
 */
private int remove_main(string[] args) {

    var assume_yes = false;
    var package_names = new Vector<string>();
    for(int i = 2; i < args.length; i++) {
        var argument = args[i];
        if(argument == "-y" || argument == "--yes") {
            assume_yes = true;
        }
        else if(argument.has_prefix("-")) {
            printerr(@"Unknown option \"$argument\"\n");
            return remove_usage();
        }
        else {
            package_names.add(argument);
        }
    }
    if(package_names.length == 0) {
        return remove_usage();
    }

    Usm.SystemState state = null;
    try {
        state = new Usm.SystemState(paths);
    }
    catch(Error e) {
        printerr(@"This system is not managed by usm: $(e.message)\n");
        return 245;
    }

    try {
        var by_package_name = new Dictionary<string, Usm.CachedPackage>();
        foreach(var installed in state.get_installed_packages()) {
            by_package_name.set(installed.package_name, state.resolve_installed(installed));
        }

        // One shared visited set across every requested target, so a
        // package reached from two cascades is removed once
        var closure = new Vector<Usm.CachedPackage>();
        var visited = new HashSet<string>();
        foreach(var package_name in package_names) {
            var target = state.find_installed(package_name);
            if(target == null) {
                printerr(@"No installed package named \"$package_name\"\n");
                return 254;
            }
            remove_collect_cascade(state, by_package_name, visited, closure, target);
        }

        var orphans = remove_collect_orphans(by_package_name, closure);

        var to_remove = new HashSet<Usm.CachedPackage>();
        to_remove.union_with(closure);
        to_remove.union_with(orphans);

        var transaction = new Usm.Transaction() {
            paths = paths,
            resource_finder = new Usm.ResourceFinder(paths),
            to_remove = to_remove,
            state = state
        };

        // Planning before the prompt lets the removal order (dependents
        // before providers, orphans last) be computed and shown
        try {
            transaction.strategise();
        }
        catch(Usm.TransactionError e) {
            printerr(@"$(e.message)\n");
            return 240;
        }

        var summary = new Usm.TransactionSummary() {
            to_remove = closure,
            orphaned_removals = orphans
        };
        if(!Usm.Cli.confirm_transaction(summary, assume_yes)) {
            print("Aborted.\n");
            return 1;
        }

        printerr("\nRunning transaction...\n");
        transaction.progress_updated.connect(transaction.print_progress);
        transaction.run();

        // The state directories go only after a successful transaction;
        // other versions' directories are never touched
        var removed_packages = closure.concat(orphans);
        foreach(var package in removed_packages) {
            Usm.Util.delete_tree(package.state_path);
        }
        print(@"Removed $(closure.length + orphans.length) package(s) ($(removed_packages.to_string(p => p.package_name, ", ")))\n");
    }
    catch(Error e) {
        printerr(@"Error: $(e.message)\n");
        return 238;
    }

    return 0;
}

/**
 * Depth-first reverse-dependency closure: {@link package} plus every
 * installed package that transitively depends on it, appended to
 * {@link closure} target-first. {@link visited} keys on the versioned
 * cache-directory name so shared dependants collapse to one removal.
 */
private void remove_collect_cascade(Usm.SystemState state, Dictionary<string, Usm.CachedPackage> by_package_name,
        HashSet<string> visited, Vector<Usm.CachedPackage> closure, Usm.CachedPackage package) throws Error {
    if(visited.contains(package.package_name)) {
        return;
    }
    visited.add(package.package_name);
    closure.add(package);

    foreach(var dependant_name in state.find_dependant_names(package)) {
        Usm.CachedPackage dependant;
        if(by_package_name.try_get(dependant_name, out dependant)) {
            remove_collect_cascade(state, by_package_name, visited, closure, dependant);
        }
    }
}

/**
 * Orphan scan over the packages {@link closure} leaves behind: every
 * implicitly installed survivor that no other survivor depends on,
 * where dependency means any runtime/build/manage/acquire ref matched
 * against the candidate's provides (the same resource-level matching
 * {@link Usm.SystemState.find_dependant_names} applies, restricted to
 * the survivors because that helper scans the whole installed set).
 * Rescans until no new orphan appears so a chain of orphans — libB
 * orphaned, then the libC only libB ever needed — is collected whole.
 */
private Vector<Usm.CachedPackage> remove_collect_orphans(Dictionary<string, Usm.CachedPackage> by_package_name,
        Vector<Usm.CachedPackage> closure) throws Error {
    // Manifests, dependency refs and explicit marks are read once up
    // front: the fixpoint loop below only consults these tables
    var manifests = new Dictionary<string, Usm.Manifest>();
    var refs_by_name = new Dictionary<string, HashSet<Usm.ResourceRef>>();
    var implicit_names = new HashSet<string>();
    foreach(var pair in by_package_name) {
        var manifest = pair.value.get_manifest();
        manifests.set(pair.key, manifest);
        refs_by_name.set(pair.key, remove_dependency_refs(manifest));
        if(!remove_explicitly_installed(pair.value)) {
            implicit_names.add(pair.key);
        }
    }

    var gone = new HashSet<string>();
    foreach(var package in closure) {
        gone.add(package.package_name);
    }

    var orphans = new Vector<Usm.CachedPackage>();
    var collected = true;
    while(collected) {
        collected = false;
        foreach(var name in implicit_names) {
            if(gone.contains(name)) {
                continue;
            }
            var provides = manifests[name].provides.select<Usm.ResourceRef>(p => p.key);
            var needed = false;
            foreach(var pair in refs_by_name) {
                if(pair.key == name || gone.contains(pair.key)) {
                    continue;
                }
                if(pair.value.any(d => provides.any(p => d.satisfied_by(p)))) {
                    needed = true;
                    break;
                }
            }
            if(needed) {
                continue;
            }
            gone.add(name);
            orphans.add(by_package_name[name]);
            collected = true;
        }
    }
    return orphans;
}

/**
 * Every dependency ref of {@link manifest} across all phases, flat plus
 * the union of all candidate groups of grouped phases.
 */
private HashSet<Usm.ResourceRef> remove_dependency_refs(Usm.Manifest manifest) {
    var refs = new HashSet<Usm.ResourceRef>();
    refs.union_with(manifest.dependencies.runtime.all_refs());
    refs.union_with(manifest.dependencies.build.all_refs());
    refs.union_with(manifest.dependencies.manage.all_refs());
    if(manifest.dependencies.acquire != null) {
        refs.union_with(manifest.dependencies.acquire.all_refs());
    }
    return refs;
}

/**
 * The package's explicit-install mark; a missing or unreadable origin
 * record means the package predates the field, whose default is false —
 * the same value the record itself would carry.
 */
private bool remove_explicitly_installed(Usm.CachedPackage package) {
    try {
        return package.get_origin_information().explicitly_installed;
    }
    catch(Error e) {
        return false;
    }
}

private int remove_usage() {
    printerr("USAGE:\n\tusm remove [-y|--yes] <packages>\n");
    return 255;
}