// exec.zig — all process execution and SSH routing
// Commands call these functions; output is streamed or captured here.
const std = @import("std");
const builtin = @import("builtin");
const types = @import("types.zig");
const errors = @import("errors.zig");
const output = @import("output.zig");

// nixos-rebuild manages this profile; generation commands must target it
// explicitly. Bare nix-env defaults to the per-user profile, which is empty.
const SYSTEM_PROFILE = "/nix/var/nix/profiles/system";

pub const RunResult = struct {
    stdout: []u8,
    stderr: []u8,
    exit_code: u8,
};

// Run a process and capture stdout+stderr (not streaming).
pub fn capture(gpa: std.mem.Allocator, io: std.Io, machine: *const types.Machine, cmd: []const []const u8) !RunResult {
    const argv = try buildArgv(gpa, machine, cmd);
    defer if (!machine.local) gpa.free(argv);

    const result = std.process.run(gpa, io, .{ .argv = argv }) catch |e| {
        errors.error_info.setMessage("process failed: {s}", .{cmd[0]});
        return e;
    };

    return .{
        .stdout = result.stdout,
        .stderr = result.stderr,
        .exit_code = switch (result.term) {
            .exited => |c| c,
            else => 1,
        },
    };
}

// Run a process and stream its output to the terminal (inherit stdio).
pub fn stream(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator, cmd: []const []const u8) !u8 {
    // The child inherits stdout and writes directly to the fd; flush any buffered
    // nina header first so it isn't reordered after the child's output.
    output.flush();
    const argv = try buildArgv(gpa, machine, cmd);
    defer if (!machine.local) gpa.free(argv);

    var child = std.process.spawn(io, .{
        .argv = argv,
        .stdin = .inherit,
        .stdout = .inherit,
        .stderr = .inherit,
    }) catch |e| {
        errors.error_info.setMessage("failed to spawn: {s}", .{cmd[0]});
        return e;
    };

    const term = child.wait(io) catch |e| {
        errors.error_info.setMessage("process wait failed", .{});
        return e;
    };

    return switch (term) {
        .exited => |c| c,
        else => 1,
    };
}

// Stream a local process with inherited stdio (no SSH routing — for nix commands).
pub fn streamLocal(io: std.Io, cmd: []const []const u8) !u8 {
    output.flush();
    var child = std.process.spawn(io, .{
        .argv = cmd,
        .stdin = .inherit,
        .stdout = .inherit,
        .stderr = .inherit,
    }) catch |e| {
        errors.error_info.setMessage("failed to spawn: {s}", .{cmd[0]});
        return e;
    };
    const term = child.wait(io) catch {
        errors.error_info.setMessage("process wait failed", .{});
        return error.ProcessFailed;
    };
    return switch (term) {
        .exited => |c| c,
        else => 1,
    };
}

// Run a process and capture output as a single string (no SSH routing — for local nix commands).
pub fn captureLocal(gpa: std.mem.Allocator, io: std.Io, cmd: []const []const u8) ![]u8 {
    const result = std.process.run(gpa, io, .{ .argv = cmd }) catch return error.ProcessFailed;
    defer gpa.free(result.stderr);
    switch (result.term) {
        .exited => |c| if (c != 0) {
            gpa.free(result.stdout);
            return error.ProcessFailed;
        },
        else => {
            gpa.free(result.stdout);
            return error.ProcessFailed;
        },
    }
    return result.stdout;
}

fn buildArgv(gpa: std.mem.Allocator, machine: *const types.Machine, cmd: []const []const u8) ![]const []const u8 {
    if (machine.local) return cmd;

    const host = machine.host orelse {
        errors.error_info.setMessage("machine '{s}' has no host configured", .{machine.name});
        return error.SshFailed;
    };

    var ssh: std.ArrayList([]const u8) = .empty;
    try ssh.append(gpa, "ssh");
    try ssh.append(gpa, "-o");
    try ssh.append(gpa, "BatchMode=yes");
    try ssh.append(gpa, "-o");
    try ssh.append(gpa, "StrictHostKeyChecking=accept-new");
    if (machine.ssh_key) |key| {
        try ssh.append(gpa, "-i");
        try ssh.append(gpa, key);
    }
    const addr = if (machine.user) |u|
        try std.fmt.allocPrint(gpa, "{s}@{s}", .{ u, host })
    else
        try gpa.dupe(u8, host);
    try ssh.append(gpa, addr);
    for (cmd) |arg| try ssh.append(gpa, arg);
    return ssh.toOwnedSlice(gpa);
}

// --- NixOS rebuild ---

pub fn nixosRebuildSwitch(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator) !u8 {
    const cmd = &.{ "sudo", "nixos-rebuild", "switch" };
    output.printSubstep("nixos-rebuild switch", .{});
    return stream(io, machine, gpa, cmd);
}

pub fn nixosRebuildDryActivate(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator) !u8 {
    return stream(io, machine, gpa, &.{ "sudo", "nixos-rebuild", "dry-activate" });
}

pub fn nixosRebuildBuild(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator) !u8 {
    return stream(io, machine, gpa, &.{ "sudo", "nixos-rebuild", "build" });
}

// --- Generations ---

// Read system-profile generations WITHOUT root. `nix-env --list-generations -p
// /nix/var/nix/profiles/system` takes a profile lock and fails as a normal user
// ("system.lock: Permission denied"). The generation symlinks themselves are
// world-readable, so list them directly: parse `system-N-link` names, take each
// link's own mtime for the date/time, and mark the one the `system` symlink
// points at as current. Output matches the `nix-env --list-generations` columns
// (num date time [current]) so parseGenerations is unchanged.
const GEN_LIST_SCRIPT =
    \\cur=$(readlink /nix/var/nix/profiles/system 2>/dev/null | sed 's/.*system-\([0-9]*\)-link/\1/'); find /nix/var/nix/profiles -maxdepth 1 -name 'system-*-link' -printf '%f %TY-%Tm-%Td %TH:%TM\n' 2>/dev/null | sed 's/system-\([0-9]*\)-link/\1/' | sort -n | awk -v c="$cur" '{ if ($1==c) print $0" current"; else print $0 }'
;

pub fn getGenerations(gpa: std.mem.Allocator, io: std.Io, machine: *const types.Machine) ![]types.GenerationInfo {
    const r = try capture(gpa, io, machine, &.{ "sh", "-c", GEN_LIST_SCRIPT });
    defer gpa.free(r.stderr);
    defer gpa.free(r.stdout);
    if (r.exit_code != 0) return error.ProcessFailed;
    return parseGenerations(gpa, r.stdout);
}

fn parseGenerations(gpa: std.mem.Allocator, output_str: []const u8) ![]types.GenerationInfo {
    var gens: std.ArrayList(types.GenerationInfo) = .empty;
    var lines = std.mem.splitScalar(u8, output_str, '\n');
    while (lines.next()) |line| {
        const trimmed = std.mem.trim(u8, line, " \t");
        if (trimmed.len == 0) continue;
        var parts = std.mem.tokenizeAny(u8, trimmed, " \t");
        const num_str = parts.next() orelse continue;
        const date_str = parts.next() orelse continue;
        const time_str = parts.next() orelse continue;
        const rest = parts.rest();
        const current = std.mem.indexOf(u8, rest, "current") != null;
        const num = std.fmt.parseInt(u32, num_str, 10) catch continue;
        try gens.append(gpa, .{
            .number = num,
            .date = try gpa.dupe(u8, date_str),
            .time = try gpa.dupe(u8, time_str),
            .current = current,
        });
    }
    return gens.toOwnedSlice(gpa);
}

pub fn getCurrentGeneration(gpa: std.mem.Allocator, io: std.Io, machine: *const types.Machine) !u32 {
    const gens = try getGenerations(gpa, io, machine);
    defer gpa.free(gens);
    for (gens) |g| {
        if (g.current) return g.number;
    }
    return 0;
}

pub fn switchGeneration(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator, n: u32) !u8 {
    // Switch the system profile to generation n, then activate it (bootloader +
    // services). Without switch-to-configuration the change isn't applied.
    const cmd = try std.fmt.allocPrint(gpa, "nix-env -p {s} --switch-generation {d} && {s}/bin/switch-to-configuration switch", .{ SYSTEM_PROFILE, n, SYSTEM_PROFILE });
    defer gpa.free(cmd);
    return stream(io, machine, gpa, &.{ "sudo", "sh", "-c", cmd });
}

pub fn rollback(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator) !u8 {
    return stream(io, machine, gpa, &.{ "sudo", "nixos-rebuild", "switch", "--rollback" });
}

pub fn deleteGeneration(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator, n: u32) !u8 {
    const n_str = try std.fmt.allocPrint(gpa, "{d}", .{n});
    defer gpa.free(n_str);
    return stream(io, machine, gpa, &.{ "sudo", "nix-env", "-p", SYSTEM_PROFILE, "--delete-generations", n_str });
}

pub fn deleteOldGenerations(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator) !u8 {
    return stream(io, machine, gpa, &.{ "sudo", "nix-env", "-p", SYSTEM_PROFILE, "--delete-generations", "old" });
}

// --- Garbage collection ---

pub fn collectGarbage(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator, delete_old: bool, keep: u32) !u8 {
    if (delete_old) {
        return stream(io, machine, gpa, &.{ "sudo", "nix-collect-garbage", "-d" });
    }
    // Keep the `keep` most recent system generations (+N deletes all but N),
    // then collect now-unreferenced store paths. `--delete-older-than` wants a
    // duration (e.g. 14d), not a generation count.
    const cmd = try std.fmt.allocPrint(gpa, "nix-env -p {s} --delete-generations +{d} && nix-collect-garbage", .{ SYSTEM_PROFILE, keep });
    defer gpa.free(cmd);
    return stream(io, machine, gpa, &.{ "sudo", "sh", "-c", cmd });
}

// --- Channels ---

pub fn channelList(gpa: std.mem.Allocator, io: std.Io, machine: *const types.Machine) ![]types.ChannelInfo {
    const r = try capture(gpa, io, machine, &.{ "nix-channel", "--list" });
    defer gpa.free(r.stderr);
    defer gpa.free(r.stdout);
    if (r.exit_code != 0) return error.ProcessFailed;
    return parseChannels(gpa, r.stdout);
}

fn parseChannels(gpa: std.mem.Allocator, output_str: []const u8) ![]types.ChannelInfo {
    var channels: std.ArrayList(types.ChannelInfo) = .empty;
    var lines = std.mem.splitScalar(u8, output_str, '\n');
    while (lines.next()) |line| {
        const trimmed = std.mem.trim(u8, line, " \t\r");
        if (trimmed.len == 0) continue;
        const space = std.mem.indexOfScalar(u8, trimmed, ' ') orelse continue;
        try channels.append(gpa, .{
            .name = try gpa.dupe(u8, trimmed[0..space]),
            .url = try gpa.dupe(u8, std.mem.trim(u8, trimmed[space + 1 ..], " \t")),
        });
    }
    return channels.toOwnedSlice(gpa);
}

pub fn channelUpdate(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator) !u8 {
    return stream(io, machine, gpa, &.{ "sudo", "nix-channel", "--update" });
}

pub fn channelAdd(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator, url: []const u8, name: []const u8) !u8 {
    return stream(io, machine, gpa, &.{ "sudo", "nix-channel", "--add", url, name });
}

pub fn channelRemove(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator, name: []const u8) !u8 {
    return stream(io, machine, gpa, &.{ "sudo", "nix-channel", "--remove", name });
}

// --- Services ---

pub fn serviceList(gpa: std.mem.Allocator, io: std.Io, machine: *const types.Machine) ![]types.ServiceInfo {
    const r = try capture(gpa, io, machine, &.{ "systemctl", "list-units", "--type=service", "--no-legend", "--no-pager" });
    defer gpa.free(r.stderr);
    defer gpa.free(r.stdout);
    if (r.exit_code != 0) return error.ProcessFailed;
    return parseServices(gpa, r.stdout);
}

fn parseServices(gpa: std.mem.Allocator, output_str: []const u8) ![]types.ServiceInfo {
    var svcs: std.ArrayList(types.ServiceInfo) = .empty;
    var lines = std.mem.splitScalar(u8, output_str, '\n');
    while (lines.next()) |line| {
        const trimmed = std.mem.trim(u8, line, " \t\r");
        if (trimmed.len == 0 or trimmed[0] == 0xE2) continue; // skip UTF-8 bullet lines
        var parts = std.mem.tokenizeAny(u8, trimmed, " \t");
        const name = parts.next() orelse continue;
        _ = parts.next(); // load
        const active_str = parts.next() orelse continue;
        const sub_str = parts.next() orelse "unknown";

        const state: types.ServiceState = if (std.mem.eql(u8, active_str, "active"))
            (if (std.mem.eql(u8, sub_str, "running") or std.mem.eql(u8, sub_str, "exited")) .active else .active)
        else if (std.mem.eql(u8, active_str, "failed"))
            .failed
        else
            .inactive;

        try svcs.append(gpa, .{
            .name = try gpa.dupe(u8, name),
            .state = state,
            .uptime = null,
        });
    }
    return svcs.toOwnedSlice(gpa);
}

pub fn serviceCtl(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator, verb: []const u8, name: []const u8) !u8 {
    // --no-pager: `systemctl status` pipes to a pager on a tty and would block.
    return stream(io, machine, gpa, &.{ "sudo", "systemctl", "--no-pager", verb, name });
}

pub fn serviceLogs(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator, name: []const u8, last: u32, follow: bool) !u8 {
    const n_str = try std.fmt.allocPrint(gpa, "{d}", .{last});
    defer gpa.free(n_str);
    if (follow) {
        return stream(io, machine, gpa, &.{ "journalctl", "-u", name, "-f" });
    }
    return stream(io, machine, gpa, &.{ "journalctl", "-u", name, "-n", n_str, "--no-pager" });
}

// --- Profile ---

pub fn profileInstall(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator, attr: []const u8) !u8 {
    const pkg_ref = try std.fmt.allocPrint(gpa, "nixpkgs#{s}", .{attr});
    defer gpa.free(pkg_ref);
    return stream(io, machine, gpa, &.{ "nix", "profile", "install", pkg_ref });
}

pub fn profileRemove(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator, attr: []const u8) !u8 {
    // `nix profile remove` matches by profile element name (e.g. "ripgrep"), not
    // by flake ref — passing nixpkgs#ripgrep matches nothing.
    return stream(io, machine, gpa, &.{ "nix", "profile", "remove", attr });
}

pub fn profileList(gpa: std.mem.Allocator, io: std.Io, machine: *const types.Machine) ![]u8 {
    const r = try capture(gpa, io, machine, &.{ "nix", "profile", "list" });
    defer gpa.free(r.stderr);
    if (r.exit_code != 0) return error.ProcessFailed;
    return r.stdout;
}

pub fn profileUpgrade(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator) !u8 {
    return stream(io, machine, gpa, &.{ "nix", "profile", "upgrade", ".*" });
}

// --- Store ---

pub fn storeGc(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator) !u8 {
    return stream(io, machine, gpa, &.{ "sudo", "nix-collect-garbage" });
}

pub fn storeVerify(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator) !u8 {
    return stream(io, machine, gpa, &.{ "nix", "store", "verify", "--all" });
}

pub const SystemStatus = struct { size: []u8, age: []u8 };

// One read-only pass for `nina status`: the current system's closure size (a
// single `path-info -S` of /run/current-system — fast, unlike -S over the whole
// store) and seconds since the system profile was last switched (its symlink
// mtime). Both are world-readable; no root needed.
const STATUS_SCRIPT =
    \\sz=$(nix path-info -S /run/current-system 2>/dev/null | awk '{print $NF}'); mt=$(stat -c %Y /nix/var/nix/profiles/system 2>/dev/null); now=$(date +%s); echo "${sz:-0} $(( ${now:-0} - ${mt:-0} ))"
;

pub fn systemStatus(gpa: std.mem.Allocator, io: std.Io, machine: *const types.Machine) SystemStatus {
    const unknown = SystemStatus{
        .size = gpa.dupe(u8, "") catch return .{ .size = "", .age = "" },
        .age = gpa.dupe(u8, "") catch return .{ .size = "", .age = "" },
    };
    const r = capture(gpa, io, machine, &.{ "sh", "-c", STATUS_SCRIPT }) catch return unknown;
    defer gpa.free(r.stdout);
    defer gpa.free(r.stderr);
    if (r.exit_code != 0) return unknown;

    var it = std.mem.tokenizeAny(u8, r.stdout, " \t\n\r");
    const sz_str = it.next() orelse return unknown;
    const age_str = it.next() orelse return unknown;
    const bytes = std.fmt.parseInt(u64, sz_str, 10) catch 0;
    const age_secs = std.fmt.parseInt(u64, age_str, 10) catch 0;

    gpa.free(unknown.size);
    gpa.free(unknown.age);
    return .{
        .size = humanSize(gpa, bytes) catch (gpa.dupe(u8, "") catch ""),
        .age = humanAgo(gpa, age_secs) catch (gpa.dupe(u8, "") catch ""),
    };
}

fn humanAgo(gpa: std.mem.Allocator, secs: u64) ![]u8 {
    if (secs < 60) return std.fmt.allocPrint(gpa, "{d}s ago", .{secs});
    if (secs < 3600) return std.fmt.allocPrint(gpa, "{d}m ago", .{secs / 60});
    if (secs < 86400) return std.fmt.allocPrint(gpa, "{d}h ago", .{secs / 3600});
    return std.fmt.allocPrint(gpa, "{d}d ago", .{secs / 86400});
}

pub fn storeRepair(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator) !u8 {
    return stream(io, machine, gpa, &.{ "sudo", "nix", "store", "repair", "--all" });
}

pub fn storeInfo(gpa: std.mem.Allocator, io: std.Io, machine: *const types.Machine) !types.StoreInfo {
    // `nix path-info -S --all` computes the CLOSURE size of every path — O(paths^2)
    // graph work that takes minutes on a real store (59k+ paths) and hangs the
    // command. We don't need closures: `--all --json` (no -S) carries each path's
    // own narSize, so one fast pass gives the path count and the summed store size.
    // `du -sh /nix/store` is just as slow on a big store, so it's gone too.
    // timeout-wrapped so a pathological store degrades to "?" instead of hanging.
    const pi = try capture(gpa, io, machine, &.{ "sh", "-c", "timeout 90 nix path-info --all --json 2>/dev/null" });
    defer gpa.free(pi.stdout);
    defer gpa.free(pi.stderr);

    const scan = scanStoreJson(pi.stdout);
    const total_owned = try humanSize(gpa, scan.total_bytes);

    return .{
        .total_size = total_owned,
        .live_paths = scan.count,
        .reclaimable_paths = 0,
    };
}

const StoreScan = struct { count: u64, total_bytes: u64 };

// One linear pass over `nix path-info --json`: each path object has exactly one
// "narSize": field, so counting them gives the true path count and summing the
// values gives the total store size — no per-path closure walk.
fn scanStoreJson(json_str: []const u8) StoreScan {
    const needle = "\"narSize\":";
    var count: u64 = 0;
    var total: u64 = 0;
    var i: usize = 0;
    while (std.mem.indexOfPos(u8, json_str, i, needle)) |pos| {
        var j = pos + needle.len;
        while (j < json_str.len and json_str[j] == ' ') : (j += 1) {}
        var val: u64 = 0;
        var any = false;
        while (j < json_str.len and json_str[j] >= '0' and json_str[j] <= '9') : (j += 1) {
            val = val * 10 + (json_str[j] - '0');
            any = true;
        }
        if (any) {
            count += 1;
            total += val;
        }
        i = j;
    }
    return .{ .count = count, .total_bytes = total };
}

fn humanSize(gpa: std.mem.Allocator, bytes: u64) ![]u8 {
    const units = [_][]const u8{ "B", "KB", "MB", "GB", "TB" };
    var val: f64 = @floatFromInt(bytes);
    var unit: usize = 0;
    while (val >= 1024.0 and unit + 1 < units.len) : (unit += 1) val /= 1024.0;
    if (unit == 0) return std.fmt.allocPrint(gpa, "{d} {s}", .{ bytes, units[0] });
    return std.fmt.allocPrint(gpa, "{d:.1} {s}", .{ val, units[unit] });
}

pub fn storePath(gpa: std.mem.Allocator, io: std.Io, machine: *const types.Machine, attr: []const u8) ![]u8 {
    // nixpkgs#<attr>, not .#<attr>: the package lives in nixpkgs (resolved via the
    // flake registry), not a flake in the current directory.
    const expr = try std.fmt.allocPrint(gpa, "nixpkgs#{s}.outPath", .{attr});
    defer gpa.free(expr);
    const r = try capture(gpa, io, machine, &.{ "nix", "eval", "--raw", expr });
    defer gpa.free(r.stderr);
    if (r.exit_code != 0) {
        gpa.free(r.stdout);
        return error.ProcessFailed;
    }
    return r.stdout;
}

// --- Flake ---

pub fn flakeUpdate(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator, input: ?[]const u8) !u8 {
    if (input) |inp| {
        return stream(io, machine, gpa, &.{ "nix", "flake", "update", inp });
    }
    return stream(io, machine, gpa, &.{ "nix", "flake", "update" });
}

pub fn flakeCheck(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator) !u8 {
    return stream(io, machine, gpa, &.{ "nix", "flake", "check" });
}

pub fn flakeInit(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator) !u8 {
    return stream(io, machine, gpa, &.{ "nix", "flake", "init" });
}

pub fn flakeLock(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator) !u8 {
    return stream(io, machine, gpa, &.{ "nix", "flake", "lock" });
}

pub fn flakeClone(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator, url: []const u8) !u8 {
    return stream(io, machine, gpa, &.{ "nix", "flake", "clone", url });
}

pub fn flakeShow(gpa: std.mem.Allocator, io: std.Io, machine: *const types.Machine) ![]u8 {
    const r = try capture(gpa, io, machine, &.{ "nix", "flake", "show", "--json" });
    defer gpa.free(r.stderr);
    if (r.exit_code != 0) {
        gpa.free(r.stdout);
        return error.ProcessFailed;
    }
    return r.stdout;
}

// --- Build / Run / Develop ---

pub fn nixBuild(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator, attr: ?[]const u8) !u8 {
    if (attr) |a| {
        const ref = try std.fmt.allocPrint(gpa, ".#{s}", .{a});
        defer gpa.free(ref);
        return stream(io, machine, gpa, &.{ "nix", "build", ref });
    }
    return stream(io, machine, gpa, &.{ "nix", "build" });
}

pub fn nixRun(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator, pkg: []const u8) !u8 {
    // nix run always gets --no-write-lock-file for remote URLs
    const is_url = std.mem.startsWith(u8, pkg, "http://") or std.mem.startsWith(u8, pkg, "https://") or std.mem.startsWith(u8, pkg, "github:");
    if (is_url) {
        return stream(io, machine, gpa, &.{ "nix", "run", pkg, "--no-write-lock-file" });
    }
    // Already a flake ref (contains '#') → use as-is; bare name → default to nixpkgs#.
    if (std.mem.indexOfScalar(u8, pkg, '#') != null) {
        return stream(io, machine, gpa, &.{ "nix", "run", pkg });
    }
    const ref = try std.fmt.allocPrint(gpa, "nixpkgs#{s}", .{pkg});
    defer gpa.free(ref);
    return stream(io, machine, gpa, &.{ "nix", "run", ref });
}

pub fn nixShell(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator, pkg: []const u8) !u8 {
    const ref = try std.fmt.allocPrint(gpa, "nixpkgs#{s}", .{pkg});
    defer gpa.free(ref);
    return stream(io, machine, gpa, &.{ "nix", "shell", ref });
}

pub fn nixDevelop(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator, run_cmd: ?[]const u8) !u8 {
    if (run_cmd) |cmd| {
        // sh -c so a multi-word command isn't treated as a single executable name.
        return stream(io, machine, gpa, &.{ "nix", "develop", "--command", "sh", "-c", cmd });
    }
    return stream(io, machine, gpa, &.{ "nix", "develop" });
}

pub fn nixRepl(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator) !u8 {
    return stream(io, machine, gpa, &.{ "nix", "repl", "--expr", "import <nixpkgs> {}" });
}

// --- Format ---

pub fn nixpkgsFmt(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator, path: []const u8, check: bool) !u8 {
    if (check) {
        return stream(io, machine, gpa, &.{ "nixpkgs-fmt", "--check", path });
    }
    return stream(io, machine, gpa, &.{ "nixpkgs-fmt", path });
}

// --- Info ---

pub fn systemInfo(gpa: std.mem.Allocator, io: std.Io, machine: *const types.Machine) ![]u8 {
    const r = try capture(gpa, io, machine, &.{"nixos-version"});
    defer gpa.free(r.stderr);
    if (r.exit_code != 0) {
        gpa.free(r.stdout);
        return error.ProcessFailed;
    }
    return r.stdout;
}

pub fn kernelInfo(gpa: std.mem.Allocator, io: std.Io, machine: *const types.Machine) ![]u8 {
    const r = try capture(gpa, io, machine, &.{ "uname", "-r" });
    defer gpa.free(r.stderr);
    if (r.exit_code != 0) {
        gpa.free(r.stdout);
        return error.ProcessFailed;
    }
    return r.stdout;
}

pub fn uptimeInfo(gpa: std.mem.Allocator, io: std.Io, machine: *const types.Machine) ![]u8 {
    const r = try capture(gpa, io, machine, &.{"uptime"});
    defer gpa.free(r.stderr);
    if (r.exit_code != 0) {
        gpa.free(r.stdout);
        return error.ProcessFailed;
    }
    return r.stdout;
}

// --- Boot ---

pub fn bootEntries(gpa: std.mem.Allocator, io: std.Io, machine: *const types.Machine) ![]types.BootEntry {
    const r = try capture(gpa, io, machine, &.{ "bootctl", "list" });
    defer gpa.free(r.stderr);
    defer gpa.free(r.stdout);
    if (r.exit_code != 0) return error.ProcessFailed;
    return parseBootEntries(gpa, r.stdout);
}

fn parseBootEntries(gpa: std.mem.Allocator, output_str: []const u8) ![]types.BootEntry {
    var entries: std.ArrayList(types.BootEntry) = .empty;
    var lines = std.mem.splitScalar(u8, output_str, '\n');
    while (lines.next()) |line| {
        const trimmed = std.mem.trim(u8, line, " \t\r");
        if (std.mem.startsWith(u8, trimmed, "title:")) {
            const title = std.mem.trim(u8, trimmed[6..], " \t");
            const current = std.mem.indexOf(u8, title, "(current)") != null;
            try entries.append(gpa, .{
                .title = try gpa.dupe(u8, title),
                .current = current,
            });
        }
    }
    return entries.toOwnedSlice(gpa);
}

// --- Pkg info ---

pub fn pkgWhy(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator, pkg: []const u8) !u8 {
    return stream(io, machine, gpa, &.{ "nix", "why-depends", ".#", pkg });
}

pub fn pkgDeps(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator, pkg: []const u8) !u8 {
    return stream(io, machine, gpa, &.{ "nix-store", "--query", "--requisites", pkg });
}

pub fn pkgSize(gpa: std.mem.Allocator, io: std.Io, machine: *const types.Machine, pkg: []const u8) ![]u8 {
    // A bare name ("ripgrep") isn't a valid installable; resolve via nixpkgs# like
    // `pkg path` does. -S -h gives closure size, human-readable. Output is
    // "<store-path>   <size>"; return just the size.
    const ref = try std.fmt.allocPrint(gpa, "nixpkgs#{s}", .{pkg});
    defer gpa.free(ref);
    const r = try capture(gpa, io, machine, &.{ "nix", "path-info", "-S", "-h", ref });
    defer gpa.free(r.stderr);
    defer gpa.free(r.stdout);
    if (r.exit_code != 0) return error.ProcessFailed;

    const line = std.mem.trim(u8, r.stdout, " \t\n\r");
    var it = std.mem.tokenizeAny(u8, line, " \t");
    _ = it.next(); // store path
    const size = std.mem.trim(u8, it.rest(), " \t");
    if (size.len == 0) return error.ProcessFailed;
    return gpa.dupe(u8, size);
}

pub fn pkgClosure(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator, pkg: []const u8) !u8 {
    return stream(io, machine, gpa, &.{ "nix", "path-info", "-rS", pkg });
}

// --- Hash / Fetch ---

pub fn nixHash(gpa: std.mem.Allocator, io: std.Io, machine: *const types.Machine, path: []const u8) ![]u8 {
    const r = try capture(gpa, io, machine, &.{ "nix", "hash", "path", path });
    defer gpa.free(r.stderr);
    if (r.exit_code != 0) {
        gpa.free(r.stdout);
        return error.ProcessFailed;
    }
    return r.stdout;
}

pub fn nixFetch(gpa: std.mem.Allocator, io: std.Io, machine: *const types.Machine, url: []const u8) ![]u8 {
    const r = try capture(gpa, io, machine, &.{ "nix-prefetch-url", url });
    defer gpa.free(r.stderr);
    if (r.exit_code != 0) {
        gpa.free(r.stdout);
        return error.ProcessFailed;
    }
    return r.stdout;
}

// --- Pin ---

pub fn editFlakeLock(_: std.mem.Allocator, _: []const u8, _: []const u8) !void {
    // Stub: full implementation would parse and edit flake.lock JSON
    // The pin/unpin flow works via nix flake update which regenerates flake.lock
}

pub fn openEditor(io: std.Io, gpa: std.mem.Allocator, editor: []const u8, path: []const u8, line: ?u32) !u8 {
    if (line) |l| {
        const line_arg = try std.fmt.allocPrint(gpa, "+{d}", .{l});
        defer gpa.free(line_arg);
        return stream(io, &types.Machine{}, gpa, &.{ editor, path, line_arg });
    }
    return stream(io, &types.Machine{}, gpa, &.{ editor, path });
}

pub fn diffClosures(io: std.Io, machine: *const types.Machine, gpa: std.mem.Allocator, a: u32, b: u32) !u8 {
    const a_str = try std.fmt.allocPrint(gpa, "/nix/var/nix/profiles/system-{d}-link", .{a});
    defer gpa.free(a_str);
    const b_str = try std.fmt.allocPrint(gpa, "/nix/var/nix/profiles/system-{d}-link", .{b});
    defer gpa.free(b_str);
    return stream(io, machine, gpa, &.{ "nix", "store", "diff-closures", a_str, b_str });
}

// --- Doctor checks ---

pub fn runDoctorChecks(gpa: std.mem.Allocator, io: std.Io, machine: *const types.Machine) ![]types.DoctorCheck {
    var checks: std.ArrayList(types.DoctorCheck) = .empty;

    // Check nix daemon
    {
        const r = try capture(gpa, io, machine, &.{ "systemctl", "is-active", "nix-daemon" });
        defer gpa.free(r.stdout);
        defer gpa.free(r.stderr);
        const active = std.mem.indexOf(u8, r.stdout, "active") != null;
        try checks.append(gpa, .{ .name = "nix daemon", .status = if (active) .ok else .fail });
    }

    // Check config syntax
    {
        const r = try capture(gpa, io, machine, &.{ "sudo", "nixos-rebuild", "dry-build" });
        defer gpa.free(r.stdout);
        defer gpa.free(r.stderr);
        try checks.append(gpa, .{ .name = "config syntax", .status = if (r.exit_code == 0) .ok else .fail });
    }

    // Check channel
    {
        const r = try capture(gpa, io, machine, &.{ "nix-channel", "--list" });
        defer gpa.free(r.stdout);
        defer gpa.free(r.stderr);
        const has_channel = r.exit_code == 0 and r.stdout.len > 0;
        try checks.append(gpa, .{ .name = "channel", .status = if (has_channel) .ok else .warn });
    }

    return checks.toOwnedSlice(gpa);
}

// --- Log ---

pub fn readNinaLog(gpa: std.mem.Allocator, io: std.Io, environ: *const std.process.Environ.Map, last: u32) ![]u8 {
    const home = environ.get("HOME") orelse return error.FileNotFound;
    const path = try std.fmt.allocPrint(gpa, "{s}/.nina.log", .{home});
    defer gpa.free(path);
    _ = last;
    return std.Io.Dir.readFileAlloc(.cwd(), io, path, gpa, .unlimited) catch return error.FileNotFound;
}

pub fn appendNinaLog(io: std.Io, environ: *const std.process.Environ.Map, entry: []const u8) void {
    const home = environ.get("HOME") orelse return;
    var path_buf: [512]u8 = undefined;
    const path = std.fmt.bufPrint(&path_buf, "{s}/.nina.log", .{home}) catch return;
    const file = std.Io.Dir.openFile(.cwd(), io, path, .{ .mode = .read_write }) catch
        (std.Io.Dir.createFile(.cwd(), io, path, .{}) catch return);
    defer file.close(io);
    const size = file.length(io) catch 0;
    file.writePositionalAll(io, entry, size) catch {};
}

// --- Update helpers ---

// Fetch a URL with curl and return the response body. Caller must free.
// error.NetworkError = DNS/connect failure; error.HttpError = non-2xx response.
pub fn fetchUrl(gpa: std.mem.Allocator, io: std.Io, url: []const u8) ![]u8 {
    const argv = [_][]const u8{
        "curl", "-s", "-L", "-w", "\nHTTP_STATUS:%{http_code}", "-m", "30", "--", url,
    };
    const result = std.process.run(gpa, io, .{ .argv = &argv }) catch return error.NetworkError;
    defer gpa.free(result.stderr);

    const marker = "\nHTTP_STATUS:";
    const mark_idx = std.mem.lastIndexOf(u8, result.stdout, marker) orelse {
        gpa.free(result.stdout);
        return error.NetworkError;
    };
    const status_str = std.mem.trim(u8, result.stdout[mark_idx + marker.len ..], " \r\n");
    const status = std.fmt.parseInt(u16, status_str, 10) catch {
        gpa.free(result.stdout);
        return error.NetworkError;
    };
    if (status == 0) { gpa.free(result.stdout); return error.NetworkError; }
    if (status < 200 or status >= 300) { gpa.free(result.stdout); return error.HttpError; }
    const body = gpa.dupe(u8, result.stdout[0..mark_idx]) catch |e| {
        gpa.free(result.stdout);
        return e;
    };
    gpa.free(result.stdout);
    return body;
}

// Download a URL to a temp file. Returns the temp path (caller must gpa.free).
// The file is written to /tmp/nina-update-<pid> and left for the caller to use.
pub fn downloadToTemp(gpa: std.mem.Allocator, io: std.Io, url: []const u8) ![]u8 {
    const tmp_path = try gpa.dupe(u8, "/tmp/nina-update.bin");
    errdefer gpa.free(tmp_path);

    var child = std.process.spawn(io, .{
        .argv = &.{ "curl", "-fsSL", "-m", "300", "-o", tmp_path, "--", url },
        .stdin = .close,
        .stdout = .close,
        .stderr = .inherit,
    }) catch return error.NetworkError;
    const term = child.wait(io) catch return error.NetworkError;
    switch (term) {
        .exited => |c| if (c != 0) return error.NetworkError,
        else => return error.NetworkError,
    }
    return tmp_path;
}

// Get the current executable path into buf. Returns slice of buf.
pub fn selfExePath(io: std.Io, buf: *[std.Io.Dir.max_path_bytes]u8) ![]const u8 {
    const len = try std.process.executablePath(io, buf);
    return buf[0..len];
}

// Verify blake3 of tmp_path against expected_hex (raw hex, no prefix), then
// atomically install the binary to install_path. Errors: ChecksumMismatch,
// AccessDenied (with error_info set), or underlying I/O errors.
pub fn verifyAndInstall(gpa: std.mem.Allocator, io: std.Io, tmp_path: []const u8, expected_hex: []const u8, install_path: []const u8) !void {
    const bytes = std.Io.Dir.readFileAlloc(.cwd(), io, tmp_path, gpa, .unlimited) catch {
        errors.error_info.setMessage("downloaded file not found: {s}", .{tmp_path});
        return error.FileNotFound;
    };
    defer gpa.free(bytes);

    var hasher = std.crypto.hash.Blake3.init(.{});
    hasher.update(bytes);
    var raw: [32]u8 = undefined;
    hasher.final(&raw);
    const hex = std.fmt.bytesToHex(raw, .lower);
    if (!std.mem.eql(u8, &hex, expected_hex)) return error.ChecksumMismatch;

    var inst_tmp_buf: [std.Io.Dir.max_path_bytes + 8]u8 = undefined;
    const inst_tmp = std.fmt.bufPrint(&inst_tmp_buf, "{s}.new", .{install_path}) catch
        return error.NameTooLong;

    {
        const f = std.Io.Dir.createFileAbsolute(io, inst_tmp, .{}) catch {
            errors.error_info.setMessage("cannot write to {s}", .{install_path});
            errors.error_info.setSuggestion("try: sudo nina update", .{});
            return error.AccessDenied;
        };
        defer f.close(io);
        f.writePositionalAll(io, bytes, 0) catch {
            errors.error_info.setMessage("cannot write to {s}", .{install_path});
            return error.AccessDenied;
        };
        try f.setPermissions(io, .fromMode(0o755));
    }
    errdefer std.Io.Dir.deleteFileAbsolute(io, inst_tmp) catch {};

    if (comptime builtin.os.tag == .macos) {
        _ = captureLocal(gpa, io, &.{ "codesign", "-f", "-s", "-", inst_tmp }) catch {};
    }

    std.Io.Dir.renameAbsolute(inst_tmp, install_path, io) catch |e| switch (e) {
        error.AccessDenied => {
            errors.error_info.setMessage("cannot replace {s}", .{install_path});
            errors.error_info.setSuggestion("try: sudo nina update", .{});
            return error.AccessDenied;
        },
        else => return e,
    };
}

// --- Nix feature setup ---

pub const NixFeatureStatus = struct {
    nix_command: bool = false,
    flakes: bool = false,

    pub fn allEnabled(self: NixFeatureStatus) bool {
        return self.nix_command and self.flakes;
    }
};

fn scanConfFeatures(conf: []const u8, status: *NixFeatureStatus) void {
    var lines = std.mem.splitScalar(u8, conf, '\n');
    while (lines.next()) |line| {
        const trimmed = std.mem.trim(u8, line, " \t");
        if (!std.mem.startsWith(u8, trimmed, "experimental-features")) continue;
        if (std.mem.indexOf(u8, trimmed, "nix-command") != null) status.nix_command = true;
        if (std.mem.indexOf(u8, trimmed, "flakes") != null) status.flakes = true;
    }
}

pub fn checkNixFeatures(gpa: std.mem.Allocator, io: std.Io, environ: *const std.process.Environ.Map) NixFeatureStatus {
    var status = NixFeatureStatus{};

    if (std.Io.Dir.readFileAlloc(.cwd(), io, "/etc/nix/nix.conf", gpa, .unlimited) catch null) |conf| {
        defer gpa.free(conf);
        scanConfFeatures(conf, &status);
    }

    if (environ.get("HOME")) |home| {
        var buf: [512]u8 = undefined;
        const path = std.fmt.bufPrint(&buf, "{s}/.config/nix/nix.conf", .{home}) catch return status;
        if (std.Io.Dir.readFileAlloc(.cwd(), io, path, gpa, .unlimited) catch null) |conf| {
            defer gpa.free(conf);
            scanConfFeatures(conf, &status);
        }
    }

    return status;
}

pub fn isNixOS(io: std.Io) bool {
    const file = std.Io.Dir.openFile(.cwd(), io, "/etc/NIXOS", .{}) catch return false;
    file.close(io);
    return true;
}

// Appends `experimental-features = nix-command flakes` to ~/.config/nix/nix.conf.
// Returns the path written (caller must free).
pub fn enableNixFeatures(gpa: std.mem.Allocator, io: std.Io, environ: *const std.process.Environ.Map) ![]const u8 {
    const home = environ.get("HOME") orelse {
        errors.error_info.setMessage("HOME not set", .{});
        return error.ConfigNotFound;
    };

    const dir_path = try std.fmt.allocPrint(gpa, "{s}/.config/nix", .{home});
    defer gpa.free(dir_path);
    const file_path = try std.fmt.allocPrint(gpa, "{s}/.config/nix/nix.conf", .{home});
    errdefer gpa.free(file_path);

    _ = captureLocal(gpa, io, &.{ "mkdir", "-p", dir_path }) catch {};

    const line = "experimental-features = nix-command flakes\n";
    const file = std.Io.Dir.openFile(.cwd(), io, file_path, .{ .mode = .read_write }) catch
        (std.Io.Dir.createFile(.cwd(), io, file_path, .{}) catch {
        errors.error_info.setMessage("could not write {s}", .{file_path});
        return error.FileNotFound;
    });
    defer file.close(io);

    const size = file.length(io) catch 0;
    file.writePositionalAll(io, line, size) catch {
        errors.error_info.setMessage("could not write {s}", .{file_path});
        return error.FileNotFound;
    };

    return file_path;
}