/*
 * Serves a commit as a downloadable archive. Writing the archive is git's
 * work, so each format here is a thin wrapper that either calls write_archive
 * directly or pipes its tar output through an external compressor. The table
 * of formats also lives here, and since a repository's snapshots mask is one
 * bit per table position, that order is part of what cgitrc means. When the
 * request carries no revision the file name is worked backwards to find one,
 * so that a link to cgit-1.2.tar.gz can serve the tag it was named after. A
 * name ending in .asc asks for the detached signature kept under refs/notes
 * instead of the archive itself.
 */

#define USE_THE_REPOSITORY_VARIABLE

#include "cgit.h"
#include "filter.h"
#include "html.h"
#include "ui-shared.h"
#include "ui-snapshot.h"

#define SIG_SUFFIX ".asc"

static int write_archive_format(const char *format_arg, const char *hex,
				const char *prefix)
{
	struct strvec argv = STRVEC_INIT;
	const char **args;
	int result;

	strvec_push(&argv, "snapshot");
	strvec_push(&argv, format_arg);
	if (prefix) {
		struct strbuf buf = STRBUF_INIT;

		strbuf_addstr(&buf, prefix);
		strbuf_addch(&buf, '/');
		strvec_push(&argv, "--prefix");
		strvec_push(&argv, buf.buf);
		strbuf_release(&buf);
	}
	strvec_push(&argv, hex);

	// write_archive rearranges the argv it is handed, which would leave
	// strvec_clear leaking or double freeing, so it gets a copy of the
	// pointers, one entry longer than argv.nr for the trailing NULL.
	args = xmalloc(sizeof(char *) * (argv.nr + 1));
	memcpy(args, argv.v, sizeof(char *) * (argv.nr + 1));

	result = write_archive(argv.nr, args, NULL, the_repository, NULL, 0);
	strvec_clear(&argv);
	free(args);
	return result;
}

static int write_tar_archive(const char *hex, const char *prefix)
{
	return write_archive_format("--format=tar", hex, prefix);
}

static int write_zip_archive(const char *hex, const char *prefix)
{
	return write_archive_format("--format=zip", hex, prefix);
}

static int write_compressed_tar_archive(const char *hex, const char *prefix,
					char *argv[])
{
	struct cgit_exec_filter filter;
	int result;

	cgit_exec_filter_init(&filter, argv[0], argv);
	cgit_open_filter(&filter.base);
	result = write_tar_archive(hex, prefix);
	cgit_close_filter(&filter.base);
	return result;
}

static int write_tar_gzip_archive(const char *hex, const char *prefix)
{
	char *argv[] = { "gzip", "-n", NULL };
	return write_compressed_tar_archive(hex, prefix, argv);
}

static int write_tar_bzip2_archive(const char *hex, const char *prefix)
{
	char *argv[] = { "bzip2", NULL };
	return write_compressed_tar_archive(hex, prefix, argv);
}

static int write_tar_lzip_archive(const char *hex, const char *prefix)
{
	char *argv[] = { "lzip", NULL };
	return write_compressed_tar_archive(hex, prefix, argv);
}

static int write_tar_xz_archive(const char *hex, const char *prefix)
{
	char *argv[] = { "xz", NULL };
	return write_compressed_tar_archive(hex, prefix, argv);
}

static int write_tar_zstd_archive(const char *hex, const char *prefix)
{
	// Single-threaded like the other compressors, since -T0 would let one
	// request pin every core.
	char *argv[] = { "zstd", NULL };
	return write_compressed_tar_archive(hex, prefix, argv);
}

// ui-shared.c reads entry zero as the tar whose signature stands in for every
// tar variant, so this order cannot change.
const struct cgit_snapshot_format cgit_snapshot_formats[] = {
	{ ".tar",	"application/x-tar",	write_tar_archive	},
	{ ".tar.gz",	"application/gzip",	write_tar_gzip_archive	},
	{ ".tar.bz2",	"application/x-bzip2",	write_tar_bzip2_archive	},
	{ ".tar.lz",	"application/x-lzip",	write_tar_lzip_archive	},
	{ ".tar.xz",	"application/x-xz",	write_tar_xz_archive	},
	{ ".tar.zst",	"application/zstd",	write_tar_zstd_archive	},
	{ ".zip",	"application/zip",	write_zip_archive	},
	{ NULL }
};

// Each tree is read the first time a signature for that format is asked for,
// then kept for the life of the process.
static struct notes_tree sig_notes[ARRAY_SIZE(cgit_snapshot_formats)];

static size_t format_index(const struct cgit_snapshot_format *f)
{
	return f - cgit_snapshot_formats;
}

static const struct cgit_snapshot_format *find_format(const char *filename)
{
	const struct cgit_snapshot_format *f;

	for (f = cgit_snapshot_formats; f->suffix; f++) {
		if (ends_with(filename, f->suffix))
			return f;
	}
	return NULL;
}

static int resolves(const char *rev)
{
	struct object_id oid;

	return repo_get_oid(the_repository, rev, &oid) == 0;
}

static const char *ref_from_filename(const struct cgit_repo *repo,
				     const char *filename,
				     const struct cgit_snapshot_format *format)
{
	struct strbuf rev = STRBUF_INIT;
	const char *repo_prefix;
	int found = 1;

	strbuf_addstr(&rev, filename);
	strbuf_setlen(&rev, rev.len - strlen(format->suffix));

	if (resolves(rev.buf))
		goto out;

	repo_prefix = cgit_snapshot_prefix(repo);
	if (starts_with(rev.buf, repo_prefix)) {
		const char *rest = rev.buf + strlen(repo_prefix);

		while (rest && (*rest == '-' || *rest == '_'))
			rest++;
		strbuf_splice(&rev, 0, rest - rev.buf, "", 0);
	}

	if (resolves(rev.buf))
		goto out;

	// A tag is often written with a leading v while the file named after it
	// is not, so that is tried last.
	strbuf_insert(&rev, 0, "v", 1);
	if (resolves(rev.buf))
		goto out;

	strbuf_splice(&rev, 0, 1, "V", 1);
	if (resolves(rev.buf))
		goto out;

	found = 0;
	strbuf_release(&rev);

out:
	return found ? strbuf_detach(&rev, NULL) : NULL;
}

static int send_snapshot(const struct cgit_snapshot_format *format,
			 const char *hex, const char *prefix,
			 const char *filename)
{
	struct object_id oid;

	if (repo_get_oid(the_repository, hex, &oid)) {
		cgit_print_error_page(404, "Not Found",
				"Bad object id: %s", hex);
		return 1;
	}
	if (!lookup_commit_reference(the_repository, &oid)) {
		cgit_print_error_page(400, "Bad Request",
				"Not a commit reference: %s", hex);
		return 1;
	}
	ctx.page.mimetype = xstrdup(format->mimetype);
	ctx.page.filename = xstrdup(filename);
	cgit_print_http_headers();
	init_archivers();
	format->write_func(hex, prefix);
	return 0;
}

static int send_sig(const struct cgit_snapshot_format *format,
		    const char *hex, const char *archive_name,
		    const char *sig_filename)
{
	const struct object_id *note = cgit_snapshot_get_sig(hex, format);
	enum object_type type;
	unsigned long size;
	char *buf;

	if (!note) {
		cgit_print_error_page(404, "Not Found",
				"No signature for %s", archive_name);
		return 0;
	}

	buf = odb_read_object(the_repository->objects, note, &type, &size);
	if (!buf) {
		cgit_print_error_page(404, "Not Found", "Not found");
		return 0;
	}

	ctx.page.untrusted = 1;
	ctx.page.mimetype = xstrdup("application/pgp-signature");
	ctx.page.filename = xstrdup(sig_filename);
	cgit_print_http_headers();

	html_raw(buf, size);
	free(buf);
	return 0;
}

const struct object_id *cgit_snapshot_get_sig(const char *ref,
					      const struct cgit_snapshot_format *f)
{
	struct notes_tree *tree;
	struct object_id oid;

	if (repo_get_oid(the_repository, ref, &oid))
		return NULL;

	tree = &sig_notes[format_index(f)];
	if (!tree->initialized) {
		struct strbuf notes_ref = STRBUF_INIT;

		// Signatures live under the format suffix with the leading dot
		// dropped, so plain tar is refs/notes/signatures/tar.
		strbuf_addf(&notes_ref, "refs/notes/signatures/%s",
			    f->suffix + 1);

		init_notes(tree, notes_ref.buf, combine_notes_ignore, 0);
		strbuf_release(&notes_ref);
	}

	return get_note(tree, &oid);
}

unsigned cgit_snapshot_format_bit(const struct cgit_snapshot_format *f)
{
	return 1U << format_index(f);
}

int cgit_parse_snapshots_mask(const char *str)
{
	struct string_list tokens = STRING_LIST_INIT_DUP;
	struct string_list_item *item;
	const struct cgit_snapshot_format *f;
	int mask = 0;

	// A number is the legacy form of this setting and is still taken
	// ahead of the named forms below.
	if (atoi(str))
		return 1;

	if (strcmp(str, "all") == 0)
		return INT_MAX;

	string_list_split(&tokens, str, " ", -1);
	string_list_remove_empty_items(&tokens, 0);

	for_each_string_list_item(item, &tokens) {
		for (f = cgit_snapshot_formats; f->suffix; f++) {
			if (!strcmp(item->string, f->suffix) ||
			    !strcmp(item->string, f->suffix + 1)) {
				mask |= cgit_snapshot_format_bit(f);
				break;
			}
		}
	}

	string_list_clear(&tokens, 0);
	return mask;
}

void cgit_print_snapshot(const char *head, const char *hex,
			 const char *filename, int dwim)
{
	const struct cgit_snapshot_format *f;
	const char *sig_filename = NULL;
	char *archive_name = NULL;
	char *prefix = NULL;

	if (!filename) {
		cgit_print_error_page(400, "Bad Request",
				"No snapshot name specified");
		return;
	}

	if (ends_with(filename, SIG_SUFFIX)) {
		sig_filename = filename;
		archive_name = xstrdup(filename);
		archive_name[strlen(archive_name) - strlen(SIG_SUFFIX)] = '\0';
		filename = archive_name;
	}

	f = find_format(filename);
	if (!f || (!sig_filename &&
		   !(ctx.repo->snapshots & cgit_snapshot_format_bit(f)))) {
		cgit_print_error_page(400, "Bad Request",
				"Unsupported snapshot format: %s", filename);
		return;
	}

	if (!hex && dwim) {
		hex = ref_from_filename(ctx.repo, filename, f);
		if (!hex) {
			cgit_print_error_page(404, "Not Found", "Not found");
			return;
		}
		prefix = xstrdup(filename);
		prefix[strlen(filename) - strlen(f->suffix)] = '\0';
	}

	if (!hex)
		hex = head;

	if (!prefix)
		prefix = xstrdup(cgit_snapshot_prefix(ctx.repo));

	if (sig_filename)
		send_sig(f, hex, filename, sig_filename);
	else
		send_snapshot(f, hex, prefix, filename);

	free(prefix);
	free(archive_name);
}