//! Turning the name of a shell into something a freshly forked child can exec,
//! and into the argv that hands that shell its prompt marks.
//!
//! Native-shell side, like temp_file.zig and message.zig, and for the same
//! reason: it touches the filesystem, and the core does not. The core carries
//! only the NAME (Pardes.shellBin, what the Shell builtin was given); which
//! family that is, what to write for it, where to write it and where the
//! binary actually lives all live here, and both frontends call it rather than
//! keeping a copy each. Nothing here imports the core, which is also what lets
//! it be its own std-only test module.
//!
//! Each host owns one `PromptRcs` for its lifetime. Its files are private
//! `mkstemp` names, completely written and closed before resolve can expose
//! them to a child. Concurrent launches therefore share neither a pathname nor
//! an inode, and a shell can never source another user's predictable /tmp file.
//!
//! ALL OF THIS RUNS IN THE PARENT. Between fork and exec a process may not
//! allocate, and a $PATH search does — which is the same reason the exec is
//! `execv` on an absolute path and never `execvp`. So the lookup is a handful
//! of `access` calls over the directories a shell actually lives in, done
//! before the fork, into a caller buffer that the child then inherits through
//! its copy of the stack.
const std = @import("std");
const builtin = @import("builtin");

const libc = std.c;
const X_OK: c_int = 1;

extern "c" fn mkstemp(template: [*:0]u8) c_int;
extern "c" fn setenv(name: [*:0]const u8, value: [*:0]const u8, overwrite: c_int) c_int;

// ------------------------------------------------- the GUI launch's PATH

/// Bounded storage for the composed PATH. /etc/paths and /etc/paths.d hold ten
/// directories on a stock machine and a handful more with third-party
/// packages; 4 KiB is not a limit anyone will meet, and a fixed buffer keeps
/// this callable from a host that has not built an allocator yet.
const path_capacity = 4096;
const max_path_files = 64;

/// macOS: give the PROCESS the PATH a login session would have, but only when
/// it plainly has not got one.
///
/// A GUI launch — Finder, the Dock, `open(1)` — inherits launchd's
/// environment, and launchd's PATH is `/usr/bin:/bin:/usr/sbin:/sbin`. Nothing
/// else: no /opt/homebrew/bin, no /usr/local/bin. A launch from a terminal
/// inherits the shell's PATH and is fine. That difference is the whole bug,
/// and it is why it reads as intermittent — the same build finds `yazi` when
/// you start it from a terminal and cannot find it when you start it from the
/// Dock.
///
/// macOS's own answer is /usr/libexec/path_helper, which reads /etc/paths and
/// /etc/paths.d. LOGIN shells run it and non-login shells do not, and pardes
/// spawns non-login shells deliberately (see `resolve`) — so a pane cannot fix
/// this for itself. Nor should it: one environ is inherited by every pty shell
/// pardes forks, every `/bin/sh -c` filter, and every language server the LSP
/// client spawns, and `binOf` searching a launchd PATH is a rust-analyzer that
/// is never found. Fixing the process fixes all of them at once.
///
/// ONLY when every entry already in PATH is a system directory. That is the
/// test for "nobody configured this". path_helper appends pre-existing entries
/// AFTER the system set, so running it over a real session's PATH would demote
/// a version manager's shims behind /usr/bin and quietly change which `node`
/// runs. A configured PATH is left exactly as it is; the launchd case is
/// unambiguous and is the only one touched.
pub fn adoptSystemPath() void {
    if (comptime builtin.os.tag != .macos) return;
    var buf: [path_capacity]u8 = undefined;
    var len: usize = 0;
    collectSystemPath(&buf, &len);
    if (len == 0) return;
    const system = buf[0..len];

    const current: []const u8 = if (libc.getenv("PATH")) |p| std.mem.span(p) else "";
    if (!allEntriesWithin(current, system)) return;
    if (std.mem.eql(u8, current, system)) return;

    var out: [path_capacity:0]u8 = undefined;
    if (len >= out.len) return;
    @memcpy(out[0..len], system);
    out[len] = 0;
    _ = setenv("PATH", out[0..len :0].ptr, 1);
}

/// Everything a native shell must do TO THE PROCESS before it forks its first
/// pane, in the order it has to happen, handing back the prompt files those
/// forks will borrow.
///
/// Four hosts performed this ritual by hand and the copies had already
/// diverged. detached/server.zig forks bash through `resolve` exactly like its
/// siblings and never set BASH_SILENCE_DEPRECATION_WARNING, so every pane in a
/// detached session on macOS opened with Apple's zsh-migration banner printed
/// across the top of it — and nobody noticed, because the three hosts anyone
/// looks at daily all had the line. That is the failure mode of a four-line
/// ritual written four times.
///
/// The ORDER is the content here. `adoptSystemPath` has to precede the fork
/// because the child inherits the environ; the setenv has to precede bash
/// because bash reads it at startup and the rc file is already too late; and
/// the rc files have to be complete on disk before any child can be handed a
/// path to one.
pub fn prepareForFork() PromptRcs {
    adoptSystemPath();
    if (comptime builtin.os.tag.isDarwin())
        _ = setenv("BASH_SILENCE_DEPRECATION_WARNING", "1", 1);
    return PromptRcs.init();
}

/// /etc/paths, then every file in /etc/paths.d in NAME ORDER, which is the
/// order path_helper reads them in and therefore the order the directories
/// take precedence in.
fn collectSystemPath(buf: []u8, len: *usize) void {
    var file_buf: [path_capacity]u8 = undefined;
    if (readSmall("/etc/paths", &file_buf)) |body| appendLines(buf, len, body);

    const io = std.Io.Threaded.global_single_threaded.io();
    var dir = std.Io.Dir.cwd().openDir(io, "/etc/paths.d", .{ .iterate = true }) catch return;
    defer dir.close(io);

    // readdir order is undefined and path_helper's is not, so the names are
    // collected and sorted before any of them is read.
    var names: [max_path_files][256]u8 = undefined;
    var name_lens: [max_path_files]usize = undefined;
    var count: usize = 0;
    var it = dir.iterate();
    while (count < names.len) {
        const entry = (it.next(io) catch break) orelse break;
        if (entry.kind == .directory) continue;
        if (entry.name.len == 0 or entry.name.len > names[count].len) continue;
        @memcpy(names[count][0..entry.name.len], entry.name);
        name_lens[count] = entry.name.len;
        count += 1;
    }
    var order: [max_path_files]usize = undefined;
    for (0..count) |i| order[i] = i;
    std.mem.sort(usize, order[0..count], Names{ .names = &names, .lens = &name_lens }, Names.lessThan);

    var path_buf: [512]u8 = undefined;
    for (order[0..count]) |i| {
        const name = names[i][0..name_lens[i]];
        const path = std.fmt.bufPrintSentinel(&path_buf, "/etc/paths.d/{s}", .{name}, 0) catch continue;
        if (readSmall(path, &file_buf)) |body| appendLines(buf, len, body);
    }
}

const Names = struct {
    names: *const [max_path_files][256]u8,
    lens: *const [max_path_files]usize,

    fn lessThan(self: Names, a: usize, b: usize) bool {
        return std.mem.order(u8, self.names[a][0..self.lens[a]], self.names[b][0..self.lens[b]]) == .lt;
    }
};

/// One directory per line, blanks and whitespace ignored — the format both
/// files use and the only thing path_helper reads out of them.
fn appendLines(buf: []u8, len: *usize, body: []const u8) void {
    var lines = std.mem.splitScalar(u8, body, '\n');
    while (lines.next()) |raw| appendEntry(buf, len, std.mem.trim(u8, raw, " \t\r"));
}

/// Append `entry` unless it is already present. Dedup preserves the FIRST
/// occurrence, which is what makes the order above mean precedence.
fn appendEntry(buf: []u8, len: *usize, entry: []const u8) void {
    if (entry.len == 0) return;
    if (hasEntry(buf[0..len.*], entry)) return;
    const separator: usize = if (len.* == 0) 0 else 1;
    if (len.* + separator + entry.len > buf.len) return;
    if (separator == 1) {
        buf[len.*] = ':';
        len.* += 1;
    }
    @memcpy(buf[len.*..][0..entry.len], entry);
    len.* += entry.len;
}

fn hasEntry(list: []const u8, entry: []const u8) bool {
    var it = std.mem.tokenizeScalar(u8, list, ':');
    while (it.next()) |have| if (std.mem.eql(u8, have, entry)) return true;
    return false;
}

/// Whether `candidate` holds nothing `list` does not. An empty candidate is
/// within any list: a process with no PATH at all is the launchd case too.
fn allEntriesWithin(candidate: []const u8, list: []const u8) bool {
    var it = std.mem.tokenizeScalar(u8, candidate, ':');
    while (it.next()) |entry| if (!hasEntry(list, entry)) return false;
    return true;
}

fn readSmall(path: [:0]const u8, buf: []u8) ?[]const u8 {
    const fd = libc.open(path, .{ .ACCMODE = .RDONLY }, @as(libc.mode_t, 0));
    if (fd < 0) return null;
    defer _ = libc.close(fd);
    var off: usize = 0;
    while (off < buf.len) {
        const n = libc.read(fd, buf[off..].ptr, buf.len - off);
        if (n < 0) {
            if (libc.errno(n) == .INTR) continue;
            return null;
        }
        if (n == 0) break;
        off += @intCast(n);
    }
    return buf[0..off];
}

test "the launchd PATH is replaced and a configured one is left alone" {
    var buf: [256]u8 = undefined;
    var len: usize = 0;
    appendEntry(&buf, &len, "/usr/bin");
    appendEntry(&buf, &len, "/bin");
    appendEntry(&buf, &len, "/usr/bin"); // already there: dedup keeps the first
    appendEntry(&buf, &len, "");
    try std.testing.expectEqualStrings("/usr/bin:/bin", buf[0..len]);

    // Exactly the launchd default, in any order: nothing here is a choice.
    try std.testing.expect(allEntriesWithin("/usr/bin:/bin", "/usr/bin:/bin:/sbin"));
    try std.testing.expect(allEntriesWithin("", "/usr/bin"));
    // One entry nobody could have inherited by accident, and the whole PATH is
    // off limits — reordering it behind /usr/bin is how a version manager stops
    // deciding which `node` runs.
    try std.testing.expect(!allEntriesWithin("/Users/x/.cargo/bin:/usr/bin", "/usr/bin:/bin"));
    try std.testing.expect(!allEntriesWithin("/opt/homebrew/bin", "/usr/bin:/bin"));
}

test "the composed system path is the real one, in path_helper's order" {
    if (comptime builtin.os.tag != .macos) return;
    var buf: [path_capacity]u8 = undefined;
    var len: usize = 0;
    collectSystemPath(&buf, &len);
    const composed = buf[0..len];
    // /etc/paths exists on every mac and leads with these.
    try std.testing.expect(hasEntry(composed, "/usr/bin"));
    try std.testing.expect(hasEntry(composed, "/bin"));
    // ...and its entries come before anything /etc/paths.d contributes, which
    // is the precedence the order encodes.
    try std.testing.expect(std.mem.startsWith(u8, composed, "/usr/local/bin:"));
    // No duplicates: /etc/paths.d files routinely repeat a system directory.
    var seen = std.mem.tokenizeScalar(u8, composed, ':');
    var index: usize = 0;
    while (seen.next()) |entry| : (index += 1) {
        var rest = std.mem.tokenizeScalar(u8, composed, ':');
        var matches: usize = 0;
        while (rest.next()) |other| if (std.mem.eql(u8, other, entry)) {
            matches += 1;
        };
        try std.testing.expectEqual(@as(usize, 1), matches);
    }
}

/// Prompt integration, per shell FAMILY rather than per binary: pardes hides
/// prompt rows, moves the cursor by clicking one, and tells a command's output
/// from the line that asked for it, and all three read the OSC 133 marks a
/// shell has to be talked into emitting. Every family needs different words
/// for the same four marks and a different way to be handed them, so the
/// binary a pane is about to exec picks one of these and there is nothing to
/// configure.
pub const ShellRc = enum { bash, fish, none };

/// Which family a shell binary belongs to, by the BASENAME's prefix — the
/// whole heuristic. A prefix and not an exact match because a real system
/// spells them `bash`, `/usr/bin/bash`, `bash-5.2`, `fish-3.7`, and pinning
/// exact names would mean a list to maintain against other people's packaging.
/// It costs a false positive on a program called `fishing`, which is a shell
/// nobody has.
///
/// `none` is not a failure: it execs the binary plain and the pane works, it
/// just has no prompt marks, so prompts are not hidden and a click on one does
/// not move the shell's cursor. Everything else about the pane is unaffected.
///
/// ponytail: two families and a fallback. zsh is the obvious third and is NOT
/// here because it is shaped differently — it has no `--rcfile`, so it needs a
/// whole ZDOTDIR directory staged with a .zshrc that re-sources the user's,
/// plus an env var set before exec. Add it when someone runs zsh in pardes and
/// misses prompt hiding; the rc text itself is four lines (precmd/preexec).
pub fn shellRc(bin: []const u8) ShellRc {
    const slash = std.mem.lastIndexOfScalar(u8, bin, '/');
    const base = if (slash) |s| bin[s + 1 ..] else bin;
    if (std.mem.startsWith(u8, base, "bash")) return .bash;
    if (std.mem.startsWith(u8, base, "fish")) return .fish;
    return .none;
}

const bash_rc =
    \\[ -f "$HOME/.bashrc" ] && source "$HOME/.bashrc"
    \\PS1='\[\e]133;A;cl=line\a\]'"$PS1"'\[\e]133;B\a\]'
    \\PROMPT_COMMAND='printf "\e]133;D\a"'"${PROMPT_COMMAND:+;$PROMPT_COMMAND}"
    \\trap 'printf "\e]133;C\a"' DEBUG
    \\
;

/// fish is handed this with `-C`, which runs AFTER config.fish — and it has to,
/// because the first thing it does is copy the user's own `fish_prompt` to call
/// it from the middle of ours. Loaded any earlier it would copy the default and
/// silently replace whatever the user actually configured.
///
/// The other half is why there is no `source ~/.config/fish/config.fish` line
/// the way the bash rc sources .bashrc: bash is being started with `--rcfile`,
/// which REPLACES its startup file, so the rc has to put it back. `-C` adds to
/// fish's startup instead of standing in for it.
///
/// C and D come off fish's own `fish_preexec`/`fish_postexec` events rather
/// than being spliced into the prompt, which is what bash's DEBUG trap is
/// working around.
const fish_rc =
    \\functions -c fish_prompt __pardes_user_prompt
    \\function fish_prompt
    \\    printf '\e]133;A;cl=line\a'
    \\    __pardes_user_prompt
    \\    printf '\e]133;B\a'
    \\end
    \\function __pardes_preexec --on-event fish_preexec
    \\    printf '\e]133;C\a'
    \\end
    \\function __pardes_postexec --on-event fish_postexec
    \\    printf '\e]133;D\a'
    \\end
    \\
;

const rc_path_capacity = 64;

/// The two complete, private prompt files a native host lends to every shell
/// it spawns. No allocation and no global name: moving this value is safe
/// because it stores lengths, never pointers into its own buffers.
pub const PromptRcs = struct {
    bash_path: [rc_path_capacity:0]u8 = @splat(0),
    bash_len: u8 = 0,
    fish_path: [rc_path_capacity:0]u8 = @splat(0),
    fish_len: u8 = 0,
    fish_command: [rc_path_capacity + "source ".len:0]u8 = @splat(0),
    fish_command_len: u8 = 0,

    pub fn init() PromptRcs {
        var rcs: PromptRcs = .{};
        rcs.bash_len = stage(&rcs.bash_path, "/tmp/pardes-osc133-bash-XXXXXX", bash_rc);
        rcs.fish_len = stage(&rcs.fish_path, "/tmp/pardes-osc133-fish-XXXXXX", fish_rc);
        if (rcs.fishPath()) |path| {
            const command = std.fmt.bufPrintSentinel(&rcs.fish_command, "source {s}", .{path}, 0) catch {
                _ = libc.unlink(path.ptr);
                rcs.fish_len = 0;
                return rcs;
            };
            rcs.fish_command_len = @intCast(command.len);
        }
        return rcs;
    }

    pub fn deinit(rcs: *PromptRcs) void {
        if (rcs.bashPath()) |path| _ = libc.unlink(path.ptr);
        if (rcs.fishPath()) |path| _ = libc.unlink(path.ptr);
        rcs.bash_len = 0;
        rcs.fish_len = 0;
        rcs.fish_command_len = 0;
    }

    fn bashPath(rcs: *const PromptRcs) ?[:0]const u8 {
        if (rcs.bash_len == 0) return null;
        return rcs.bash_path[0..rcs.bash_len :0];
    }

    fn fishPath(rcs: *const PromptRcs) ?[:0]const u8 {
        if (rcs.fish_len == 0) return null;
        return rcs.fish_path[0..rcs.fish_len :0];
    }

    fn fishCommand(rcs: *const PromptRcs) ?[:0]const u8 {
        if (rcs.fish_command_len == 0) return null;
        return rcs.fish_command[0..rcs.fish_command_len :0];
    }
};

/// Create one private 0600 file and reveal its length only after the complete
/// write and close. Failure leaves no pathname for resolve to hand to a shell.
fn stage(path_buf: *[rc_path_capacity:0]u8, template: []const u8, contents: []const u8) u8 {
    const path = std.fmt.bufPrintSentinel(path_buf, "{s}", .{template}, 0) catch return 0;
    const fd = mkstemp(path.ptr);
    if (fd < 0) return 0;
    var off: usize = 0;
    while (off < contents.len) {
        const n = libc.write(fd, contents[off..].ptr, contents.len - off);
        if (n < 0) {
            if (libc.errno(n) == .INTR) continue;
            _ = libc.close(fd);
            _ = libc.unlink(path.ptr);
            return 0;
        }
        if (n == 0) {
            _ = libc.close(fd);
            _ = libc.unlink(path.ptr);
            return 0;
        }
        off += @intCast(n);
    }
    if (libc.close(fd) != 0) {
        _ = libc.unlink(path.ptr);
        return 0;
    }
    return @intCast(path.len);
}

test "shell family is the basename's prefix, and anything else runs unadorned" {
    try std.testing.expectEqual(ShellRc.fish, shellRc("fish"));
    try std.testing.expectEqual(ShellRc.fish, shellRc("/usr/bin/fish"));
    try std.testing.expectEqual(ShellRc.fish, shellRc("/opt/homebrew/bin/fish"));
    try std.testing.expectEqual(ShellRc.bash, shellRc("bash"));
    try std.testing.expectEqual(ShellRc.bash, shellRc("/bin/bash"));
    // packaged with a version on the end, which is why this is a prefix
    try std.testing.expectEqual(ShellRc.bash, shellRc("/usr/bin/bash-5.2"));
    try std.testing.expectEqual(ShellRc.fish, shellRc("/usr/local/bin/fish-3.7"));
    // a directory that merely CONTAINS the word is not the shell's name
    try std.testing.expectEqual(ShellRc.none, shellRc("/opt/fish/bin/nu"));
    // no marks, still a shell
    try std.testing.expectEqual(ShellRc.none, shellRc("/usr/bin/zsh"));
    try std.testing.expectEqual(ShellRc.none, shellRc("/bin/sh"));
    try std.testing.expectEqual(ShellRc.none, shellRc("nu"));
    try std.testing.expectEqual(ShellRc.none, shellRc(""));
}

/// The directories a shell binary is actually installed in. Not $PATH: see the
/// header. `/opt/homebrew` and `/opt/local` are where a mac keeps the shells
/// that did not ship with it, which is every shell anyone chooses on purpose.
const bin_dirs = [_][]const u8{
    "/usr/bin/",
    "/bin/",
    "/usr/local/bin/",
    "/opt/homebrew/bin/",
    "/opt/local/bin/",
    "/usr/sbin/",
};

/// Last resorts, in order, when the configured shell is not installed: the
/// shell pardes used to hardcode, then the one POSIX says exists. A pane that
/// opens with the wrong shell beats a pane whose child dies at exec and shows
/// nothing but an immediate EOF.
const fallbacks = [_][]const u8{
    if (builtin.os.tag == .linux) "/usr/bin/bash" else "/bin/bash",
    "/bin/sh",
};

pub const Spawn = struct {
    path: [*:0]const u8,
    /// argv for execv. Shorter forms stop at their first null, which is what
    /// execv reads anyway, so one width covers all three families.
    argv: [4:null]?[*:0]const u8,
};

/// `bin` is whatever the Shell builtin was given — a bare name to look up, or
/// a path (anything with a `/`) to take at its word. `buf` holds the resolved
/// path for as long as the returned Spawn is used, which for a caller that is
/// about to fork means: until the child execs. `prompt_rcs` is host-lifetime
/// storage and must likewise remain alive through that exec.
pub fn resolve(bin: []const u8, buf: *[std.fs.max_path_bytes]u8, prompt_rcs: *const PromptRcs) Spawn {
    const path = find(bin, buf) orelse fallback(buf);
    // the family comes off the path that will ACTUALLY be executed, not the
    // name that was asked for — `Shell sh` on a system where that is a symlink
    // to bash still has no `--rcfile` promise attached to it, and a resolved
    // /usr/bin/fish reads as fish whether it was reached by name or by path
    const marks: [2]?[*:0]const u8 = switch (shellRc(std.mem.span(path))) {
        .bash => if (prompt_rcs.bashPath()) |rc| .{ "--rcfile", rc.ptr } else .{ null, null },
        // -C runs AFTER config.fish, which is the whole point (see fish_rc)
        .fish => if (prompt_rcs.fishCommand()) |command| .{ "-C", command.ptr } else .{ null, null },
        .none => .{ null, null },
    };
    return .{ .path = path, .argv = .{ path, marks[0], marks[1], null } };
}

fn find(bin: []const u8, buf: *[std.fs.max_path_bytes]u8) ?[*:0]const u8 {
    if (bin.len == 0 or bin.len + 1 > buf.len) return null;
    if (std.mem.indexOfScalar(u8, bin, '/') != null) {
        @memcpy(buf[0..bin.len], bin);
        buf[bin.len] = 0;
        const p: [*:0]const u8 = @ptrCast(buf);
        return if (libc.access(p, X_OK) == 0) p else null;
    }
    for (bin_dirs) |dir| {
        if (dir.len + bin.len + 1 > buf.len) continue;
        @memcpy(buf[0..dir.len], dir);
        @memcpy(buf[dir.len..][0..bin.len], bin);
        buf[dir.len + bin.len] = 0;
        const p: [*:0]const u8 = @ptrCast(buf);
        if (libc.access(p, X_OK) == 0) return p;
    }
    return null;
}

fn fallback(buf: *[std.fs.max_path_bytes]u8) [*:0]const u8 {
    for (fallbacks) |f| {
        @memcpy(buf[0..f.len], f);
        buf[f.len] = 0;
        const p: [*:0]const u8 = @ptrCast(buf);
        if (libc.access(p, X_OK) == 0) return p;
    }
    // nothing executable anywhere we know to look: exec will fail and the pane
    // will show an immediate EOF, which is the honest report of that machine.
    // buf already holds the last candidate, NUL and all.
    return @ptrCast(buf);
}

test "a path is taken at its word, a name is looked up, and both pick their own marks" {
    if (builtin.os.tag == .windows) return;
    var buf: [std.fs.max_path_bytes]u8 = undefined;
    var prompt_rcs = PromptRcs.init();
    defer prompt_rcs.deinit();

    // /bin/sh exists on every unix this builds for and is in no family, so it
    // pins the resolve-by-path arm AND the unadorned argv
    const sh = resolve("/bin/sh", &buf, &prompt_rcs);
    try std.testing.expectEqualStrings("/bin/sh", std.mem.span(sh.path));
    try std.testing.expect(sh.argv[1] == null);

    // a name with no slash is searched for; whatever it resolves to, it is a
    // bash and so carries --rcfile pointing at the rc the shells write
    const bash = resolve("bash", &buf, &prompt_rcs);
    try std.testing.expect(shellRc(std.mem.span(bash.path)) == .bash);
    try std.testing.expectEqualStrings("--rcfile", std.mem.span(bash.argv[1].?));
    try std.testing.expectEqualStrings(prompt_rcs.bashPath().?, std.mem.span(bash.argv[2].?));

    // nothing is installed under this name, so the fallback answers — and the
    // fallback is a real executable, not the name that failed
    const missing = resolve("zznosuchshell", &buf, &prompt_rcs);
    try std.testing.expect(!std.mem.eql(u8, "zznosuchshell", std.mem.span(missing.path)));
    try std.testing.expect(libc.access(missing.path, X_OK) == 0);

    // an absolute path that does not exist falls back too, rather than being
    // handed to exec to fail on
    const gone = resolve("/zz/no/such/shell", &buf, &prompt_rcs);
    try std.testing.expect(libc.access(gone.path, X_OK) == 0);
}

test "prompt rc owners have private complete files and clean them up" {
    if (builtin.os.tag == .windows) return;
    var a = PromptRcs.init();
    defer a.deinit();
    var b = PromptRcs.init();
    defer b.deinit();
    const a_bash = a.bashPath() orelse return error.TempCreateFailed;
    const b_bash = b.bashPath() orelse return error.TempCreateFailed;
    const a_fish = a.fishPath() orelse return error.TempCreateFailed;
    try std.testing.expect(!std.mem.eql(u8, a_bash, b_bash));
    const fish_command = a.fishCommand() orelse return error.MissingFishCommand;
    try std.testing.expectEqualStrings("source ", fish_command[0.."source ".len]);
    try std.testing.expectEqualStrings(a_fish, fish_command["source ".len..]);

    var buf: [bash_rc.len]u8 = undefined;
    const fd = libc.open(a_bash.ptr, .{ .ACCMODE = .RDONLY });
    if (fd < 0) return error.OpenFailed;
    defer _ = libc.close(fd);
    var len: usize = 0;
    while (len < buf.len) {
        const n = libc.read(fd, buf[len..].ptr, buf.len - len);
        if (n < 0) {
            if (libc.errno(n) == .INTR) continue;
            return error.ReadFailed;
        }
        if (n == 0) break;
        len += @intCast(n);
    }
    try std.testing.expectEqualStrings(bash_rc, buf[0..len]);

    var removed: [rc_path_capacity:0]u8 = @splat(0);
    @memcpy(removed[0..a_bash.len], a_bash);
    removed[a_bash.len] = 0;
    a.deinit();
    try std.testing.expect(libc.access(&removed, 0) < 0);
}