const std = @import("std");

const cdl = @import("root.zig");

/// owned
pub fn hostname() ![]const u8 {
    var buf: [std.posix.HOST_NAME_MAX]u8 = undefined;
    const hostname_buf = try std.posix.gethostname(&buf);
    return try cdl.gpa.dupe(u8, hostname_buf);
}

pub fn user() !?[]const u8 {
    const pwinfo = try PWInfo.get();
    if (pwinfo) |pw| return pw.user;

    if (cdl.environ_map) |envmap| return envmap.get("USER");
    if (cdl.environ_map) |envmap| return envmap.get("LOGNAME");

    return null;
}

pub fn shell() !?[]const u8 {
    const shell_str = blk: {
        const pwinfo = try PWInfo.get();
        if (pwinfo) |pw| break :blk pw.shell;

        break :blk if (cdl.environ_map) |envmap|
            envmap.get("SHELL")
        else
            null;
    } orelse return null;

    if (std.mem.cutScalarLast(u8, shell_str, '/')) |parts|
        return parts[1];

    return shell_str;
}

pub fn osname() !?[]const u8 {
    const f = try std.Io.Dir.openFileAbsolute(cdl.io, "/etc/os-release", .{});

    var buf: [0x1000]u8 = undefined;
    var file_reader = f.reader(cdl.io, &buf);
    var reader = &file_reader.interface;

    while (try reader.takeDelimiter('\n')) |line|
        if (std.mem.cutPrefix(u8, line, "NAME=")) |name|
            return try cdl.allocator.dupe(u8, trimquotes(name));
    return null;
}

pub fn desktop() ?[]const u8 {
    if (cdl.environ_map) |envmap| return envmap.get("XDG_CURRENT_DESKTOP");
    return null;
}

pub fn session() ?[]const u8 {
    if (cdl.environ_map) |envmap| return envmap.get("XDG_SESSION_TYPE");
    return null;
}

pub fn terminal() ?[]const u8 {
    if (cdl.environ_map) |envmap| return envmap.get("TERMINAL");
    const nterm: ?[]const u8 = blk: {
        const termenv = if (cdl.environ_map) |envmap| envmap.get("TERM") else null;
        if (termenv) |term| if (term.len > 0) if (std.mem.findScalar(u8, term, '-')) |i|
            break :blk term[0..i]
        else
            break :blk term;
        break :blk null;
    };
    if (nterm) |term| if (!std.mem.eql(u8, term, "xterm") and !std.mem.eql(u8, term, "linux"))
        return term;

    return null;
}

pub fn editor() ?[]const u8 {
    if (cdl.environ_map) |envmap| return envmap.get("EDITOR");
    return null;
}

const PWInfo = struct {
    user: ?[]const u8,
    shell: ?[]const u8,
    dir: ?[]const u8,

    var cached: ?@This() = null;

    pub fn get() !?PWInfo {
        if (PWInfo.cached) |c| return c;

        const f = try std.Io.Dir.openFileAbsolute(cdl.io, "/etc/passwd", .{});

        var buf: [0x1000]u8 = undefined;
        var file_reader = f.reader(cdl.io, &buf);
        var reader = &file_reader.interface;

        const uid = std.os.linux.getuid();
        w: while (try reader.takeDelimiter('\n')) |line| {
            var parts = std.mem.splitScalar(u8, line, ':');
            var pw_user: ?[]const u8 = null;
            var pw_shell: ?[]const u8 = null;
            var pw_dir: ?[]const u8 = null;

            var i: usize = 0;
            while (parts.next()) |part| : (i = i + 1) switch (i) {
                0 => pw_user = part,
                2 => if (try std.fmt.parseInt(u32, part, 10) != uid) continue :w,
                5 => pw_dir = part,
                6 => pw_shell = part,
                else => {},
            };

            return .{
                .user = if (pw_user) |user_| try cdl.allocator.dupe(u8, user_) else null,
                .shell = if (pw_shell) |shell_| try cdl.allocator.dupe(u8, shell_) else null,
                .dir = if (pw_dir) |dir_| try cdl.allocator.dupe(u8, dir_) else null,
            };
        }

        return null;
    }
};

// helpers ====================================================================

fn trimquotes(s: []const u8) []const u8 {
    if (s.len < 2) return s;
    const open = switch (s[0]) {
        '"' => s[0],
        '\'' => s[0],
        else => return s,
    };
    // assume malformed
    if (s[s.len - 1] != open) return s[1..];
    return s[1 .. s.len - 1];
}

test "trim quotes" {
    try std.testing.expectEqualStrings("meow", trimquotes("meow"));
    try std.testing.expectEqualStrings("meow", trimquotes(
        \\"meow"
    ));
    try std.testing.expectEqualStrings("meow", trimquotes(
        \\'meow'
    ));
    try std.testing.expectEqualStrings("meow", trimquotes(
        \\'meow
    ));
    try std.testing.expectEqualStrings("meow", trimquotes(
        \\"meow
    ));
}