const std = @import("std");
const mem = std.mem;
const fmt = std.fmt;
const maxInt = std.math.maxInt;
const Allocator = mem.Allocator;
const ArrayList = std.ArrayList;
const BoundedArray = std.BoundedArray;

const pw_passwd = "x\x00";

const User = @This();
const ErrCtx = @import("ErrCtx.zig");
const PackedUser = @import("PackedUser.zig");
const validate = @import("validate.zig");

uid: u32,
gid: u32,
name: []const u8,
gecos: []const u8,
home: []const u8,
shell: []const u8,

// deep-clones a User record with a given Allocator.
pub fn clone(
    self: *const User,
    allocator: Allocator,
) error{OutOfMemory}!User {
    const name = try allocator.dupe(u8, self.name);
    errdefer allocator.free(name);
    const gecos = try allocator.dupe(u8, self.gecos);
    errdefer allocator.free(gecos);
    const home = try allocator.dupe(u8, self.home);
    errdefer allocator.free(home);
    const shell = try allocator.dupe(u8, self.shell);
    errdefer allocator.free(shell);

    return User{
        .uid = self.uid,
        .gid = self.gid,
        .name = name,
        .gecos = gecos,
        .home = home,
        .shell = shell,
    };
}

// fromLine accepts a line of /etc/passwd (with or without the EOL) and makes a
// User.
fn fromLine(allocator: Allocator, err: *ErrCtx, line: []const u8) error{ InvalidRecord, OutOfMemory }!User {
    var it = mem.split(u8, line, ":");
    const name = it.next() orelse return err.returnf("too few fields", .{}, error.InvalidRecord);
    _ = it.next() orelse return err.returnf("too few fields", .{}, error.InvalidRecord); // password
    const uids = it.next() orelse return err.returnf("too few fields", .{}, error.InvalidRecord);
    const gids = it.next() orelse return err.returnf("too few fields", .{}, error.InvalidRecord);
    const gecos = it.next() orelse return err.returnf("too few fields", .{}, error.InvalidRecord);
    const home = it.next() orelse return err.returnf("too few fields", .{}, error.InvalidRecord);
    const shell = it.next() orelse return err.returnf("too few fields", .{}, error.InvalidRecord);
    if (it.next() != null) return err.returnf("too many fields", .{}, error.InvalidRecord);

    const uid = fmt.parseInt(u32, uids, 10) catch
        return err.returnf("bad uid: {s}", .{uids}, error.InvalidRecord);

    const gid = fmt.parseInt(u32, gids, 10) catch
        return err.returnf("bad gid: {s}", .{gids}, error.InvalidRecord);

    validate.name(name, err) catch
        return err.returnf("invalid name '{s}'", .{name}, error.InvalidRecord);
    validate.gecos(gecos, err) catch
        return err.returnf("invalid gecos '{s}'", .{gecos}, error.InvalidRecord);
    validate.path(home, err) catch
        return err.returnf("invalid home '{s}'", .{home}, error.InvalidRecord);
    validate.path(shell, err) catch
        return err.returnf("invalid shell '{s}'", .{shell}, error.InvalidRecord);

    const user = User{
        .uid = uid,
        .gid = gid,
        .name = name,
        .gecos = gecos,
        .home = home,
        .shell = shell,
    };
    return try user.clone(allocator);
}

fn strlen(self: *const User) usize {
    return self.name.len +
        self.gecos.len +
        self.home.len +
        self.shell.len;
}

const line_fmt = "{s}:x:{d}:{d}:{s}:{s}:{s}\n";

pub const max_line_len = fmt.count(line_fmt, .{
    max_user.name,
    max_user.uid,
    max_user.gid,
    max_user.gecos,
    max_user.home,
    max_user.shell,
});

// toLine formats the user in /etc/passwd format, including the EOL
pub fn toLine(self: *const User) BoundedArray(u8, max_line_len) {
    var result = BoundedArray(u8, max_line_len).init(0) catch unreachable;
    result.writer().print(line_fmt, .{
        self.name,
        self.uid,
        self.gid,
        self.gecos,
        self.home,
        self.shell,
    }) catch unreachable;
    return result;
}

// length of all string-data fields, assuming they are zero-terminated.
// Does not include password, since that's always static 'x\00'.
pub fn strlenZ(self: *const User) usize {
    return self.strlen() + 4; // '\0' of name, gecos, home and shell
}

pub fn deinit(self: *User, allocator: Allocator) void {
    allocator.free(self.name);
    allocator.free(self.gecos);
    allocator.free(self.home);
    allocator.free(self.shell);
    self.* = undefined;
}

pub fn fromReader(allocator: Allocator, err: *ErrCtx, reader: anytype) ![]User {
    var users = ArrayList(User).init(allocator);
    errdefer {
        for (users.items) |*user| user.deinit(allocator);
        users.deinit();
    }

    var buf: [max_line_len]u8 = undefined;
    while (try reader.readUntilDelimiterOrEof(buf[0..], '\n')) |line| {
        var user = try fromLine(allocator, err, line);
        try users.append(user);
    }
    return users.toOwnedSlice();
}

pub const CUser = extern struct {
    pw_name: [*:0]const u8,
    pw_passwd: [*:0]const u8 = pw_passwd,
    pw_uid: u32,
    pw_gid: u32,
    pw_gecos: [*:0]const u8,
    pw_dir: [*:0]const u8,
    pw_shell: [*:0]const u8,
};

const testing = std.testing;

pub const max_user = User{
    .uid = maxInt(u32),
    .gid = maxInt(u32),
    .name = "Name" ** 8,
    .gecos = "realname" ** 255 ++ "realnam",
    .home = "Home" ** 16,
    .shell = "She.LllL" ** 32,
};

test "User.fromLine" {
    const examples = [_]struct {
        line: []const u8,
        want: ?User = null,
        wantErr: []const u8 = &[_]u8{},
    }{
        .{
            .line = "root:x:0:0:root:/root:/bin/bash",
            .want = User{
                .uid = 0,
                .gid = 0,
                .name = "root",
                .gecos = "root",
                .home = "/root",
                .shell = "/bin/bash",
            },
        },
        .{
            .line = "žemas:x:0:0:root:/root:/bin/bash",
            .wantErr = "invalid name 'žemas': invalid character 0xC5 at position 0",
        },
        .{
            .line = "root:x:-1:0:root:/root:/bin/bash",
            .wantErr = "bad uid: -1",
        },
        .{
            .line = "root:x:0:-1:root:/root:/bin/bash",
            .wantErr = "bad gid: -1",
        },
        .{
            .line = "root:x:0:0:root:/root:bin/bash",
            .wantErr = "invalid shell 'bin/bash': must start with /",
        },
        .{
            .line = "root:x:0:0:root:/root:/bin/bash:redundant",
            .wantErr = "too many fields",
        },
        .{
            .line = "",
            .wantErr = "too few fields",
        },
        .{
            .line = "root:x:0:0:root:/root",
            .wantErr = "too few fields",
        },
    };

    const allocator = testing.allocator;
    for (examples) |tt| {
        var err = ErrCtx{};

        if (tt.want) |want_user| {
            var got = try fromLine(allocator, &err, tt.line);
            defer got.deinit(allocator);
            try testing.expectEqual(want_user.uid, got.uid);
            try testing.expectEqual(want_user.gid, got.gid);
            try testing.expectEqualStrings(want_user.name, got.name);
            try testing.expectEqualStrings(want_user.gecos, got.gecos);
            try testing.expectEqualStrings(want_user.home, got.home);
            try testing.expectEqualStrings(want_user.shell, got.shell);
            continue;
        }

        const got = fromLine(allocator, &err, tt.line);
        try testing.expectError(error.InvalidRecord, got);
        try testing.expectEqualStrings(tt.wantErr, err.unwrap().constSlice());
    }
}

test "User max_user and max_str_len are consistent" {
    const total_len = max_user.name.len +
        max_user.gecos.len +
        max_user.home.len +
        max_user.shell.len;
    try testing.expectEqual(total_len, PackedUser.max_str_len);
}

test "User.clone" {
    var allocator = testing.allocator;
    const user = User{
        .uid = 1000,
        .gid = 1000,
        .name = "vidmantas",
        .gecos = "Vidmantas Kaminskas",
        .home = "/home/vidmantas",
        .shell = "/bin/bash",
    };
    var user2 = try user.clone(allocator);
    defer user2.deinit(allocator);

    try testing.expectEqualStrings(user.shell, "/bin/bash");
}