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 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 stringdata = try allocator.alloc(u8, self.strlen());
    const gecos_start = self.name.len;
    const home_start = gecos_start + self.gecos.len;
    const shell_start = home_start + self.home.len;
    mem.copy(u8, stringdata[0..self.name.len], self.name);
    mem.copy(u8, stringdata[gecos_start..], self.gecos);
    mem.copy(u8, stringdata[home_start..], self.home);
    mem.copy(u8, stringdata[shell_start..], self.shell);

    return User{
        .uid = self.uid,
        .gid = self.gid,
        .name = stringdata[0..self.name.len],
        .gecos = stringdata[gecos_start .. gecos_start + self.gecos.len],
        .home = stringdata[home_start .. home_start + self.home.len],
        .shell = stringdata[shell_start .. shell_start + self.shell.len],
    };
}

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

    const uid = fmt.parseInt(u32, uids, 10) catch return error.InvalidRecord;
    const gid = fmt.parseInt(u32, gids, 10) catch return error.InvalidRecord;

    try validate.utf8(name);
    try validate.utf8(gecos);
    try validate.utf8(home);
    try validate.utf8(shell);

    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";

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(max_line_len) catch unreachable;
    _ = fmt.bufPrint(result.slice(), 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 {
    const slice = self.home.ptr[0..self.strlen()];
    allocator.free(slice);
    self.* = undefined;
}

pub fn fromReader(allocator: Allocator, reader: anytype) ![]User {
    var users = ArrayList(User).init(allocator);
    var buf: [max_line_len + 1]u8 = undefined;
    // TODO: catch and interpret error
    while (try reader.readUntilDelimiterOrEof(buf[0..], '\n')) |line| {
        const user = try fromLine(allocator, line);
        try users.append(user);
    }
    return users.toOwnedSlice();
}

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