//! Release payload staging for `zig build dist` (milestone-14 rulings 3 and 4).
//!
//! Two modes, both writing only into paths the build system handed them:
//!
//!   dist_stage stage --out <dir> --binary <path> --service <path>
//!                    --sysusers <path> --license <path> --install-md <path>
//!                    --licenses <dir>
//!
//!     Fills `<dir>` with the six files of the tarball payload, each with the
//!     mode the release specifies. `THIRD-PARTY-NOTICES` is concatenated from
//!     the reviewed inventory at `<licenses>/inventory.zon`; it is never
//!     scraped from the dependency tree, because a generated notices file that
//!     nobody reads rots silently into a false statement.
//!
//!   dist_stage sums --out <file> [--entry <name> <path>]...
//!
//!     Writes `sha256sum`-format lines, one per `--entry`, in argument order.
//!     `<name>` is the name the asset carries in the release, not the cache
//!     path the bytes were read from.
//!
//! Modes are set with an explicit `setPermissions` after creation rather than
//! through the creation mode, which the process umask would mask.

const std = @import("std");
const Allocator = std.mem.Allocator;
const Io = std.Io;

const max_input_bytes = 256 << 20;

/// One reviewed component of the shipped artifacts. The build system owns this
/// shape; `licenses/inventory.zon` is a tuple of these, in the order they
/// should appear in `THIRD-PARTY-NOTICES`.
/// Mirrors `Entry` in `src/licenses_drift_test.zig`, which type-checks the same
/// file at compile time. The two must agree; a mismatch fails one of them.
const Component = struct {
    /// The component as an operator would name it.
    component: []const u8,
    /// The version(s) actually shipped.
    version: []const u8,
    /// Why its licence applies to what we ship, and which option was taken
    /// when the component offers a choice.
    note: []const u8,
    /// Licence text, relative to `licenses/`.
    file: []const u8,
};

const PayloadFile = struct {
    name: []const u8,
    mode: std.posix.mode_t,
};

const payload_dir_mode: std.posix.mode_t = 0o755;

pub fn main(init: std.process.Init) !void {
    const arena = init.arena.allocator();
    const io = init.io;
    const args = try init.minimal.args.toSlice(arena);
    if (args.len < 2) std.process.fatal("usage: dist_stage <stage|sums> ...", .{});

    if (std.mem.eql(u8, args[1], "stage")) return stage(arena, io, args[2..]);
    if (std.mem.eql(u8, args[1], "sums")) return sums(arena, io, args[2..]);
    std.process.fatal("unknown mode '{s}': expected `stage` or `sums`", .{args[1]});
}

fn stage(arena: Allocator, io: Io, args: []const []const u8) !void {
    var out_path: ?[]const u8 = null;
    var binary: ?[]const u8 = null;
    var service: ?[]const u8 = null;
    var sysusers: ?[]const u8 = null;
    var license: ?[]const u8 = null;
    var install_md: ?[]const u8 = null;
    var licenses: ?[]const u8 = null;

    var i: usize = 0;
    while (i < args.len) : (i += 2) {
        if (i + 1 >= args.len) std.process.fatal("'{s}' needs a value", .{args[i]});
        const value = args[i + 1];
        const flag = args[i];
        if (std.mem.eql(u8, flag, "--out")) {
            out_path = value;
        } else if (std.mem.eql(u8, flag, "--binary")) {
            binary = value;
        } else if (std.mem.eql(u8, flag, "--service")) {
            service = value;
        } else if (std.mem.eql(u8, flag, "--sysusers")) {
            sysusers = value;
        } else if (std.mem.eql(u8, flag, "--license")) {
            license = value;
        } else if (std.mem.eql(u8, flag, "--install-md")) {
            install_md = value;
        } else if (std.mem.eql(u8, flag, "--licenses")) {
            licenses = value;
        } else {
            std.process.fatal("unknown flag '{s}'", .{flag});
        }
    }

    // `iterate` is what makes the handle usable with `setPermissions`
    // (Io/Dir.zig:1941), which the payload directory's own mode needs.
    var out = Io.Dir.cwd().openDir(io, required(out_path, "--out"), .{ .iterate = true }) catch |err| {
        std.process.fatal("cannot open --out directory '{s}': {t}", .{ out_path.?, err });
    };
    defer out.close(io);

    const notices = try renderNotices(arena, io, required(licenses, "--licenses"));

    try copyInto(arena, io, out, .{ .name = "nxdns", .mode = 0o755 }, required(binary, "--binary"));
    try copyInto(arena, io, out, .{ .name = "nxdns.service", .mode = 0o644 }, required(service, "--service"));
    try copyInto(arena, io, out, .{ .name = "nxdns.conf", .mode = 0o644 }, required(sysusers, "--sysusers"));
    try copyInto(arena, io, out, .{ .name = "LICENSE", .mode = 0o644 }, required(license, "--license"));
    try copyInto(arena, io, out, .{ .name = "INSTALL.md", .mode = 0o644 }, required(install_md, "--install-md"));
    try writeInto(io, out, .{ .name = "THIRD-PARTY-NOTICES", .mode = 0o644 }, notices);

    // The payload directory is a tar member too, and the mode `--out` was
    // created with came from the build runner's umask.
    out.setPermissions(io, .fromMode(payload_dir_mode)) catch |err| {
        std.process.fatal("cannot set the mode of '{s}': {t}", .{ out_path.?, err });
    };
}

fn sums(arena: Allocator, io: Io, args: []const []const u8) !void {
    var out_path: ?[]const u8 = null;
    var line_buffer: std.Io.Writer.Allocating = try .initCapacity(arena, 256);

    var i: usize = 0;
    while (i < args.len) {
        if (std.mem.eql(u8, args[i], "--out")) {
            if (i + 1 >= args.len) std.process.fatal("'--out' needs a value", .{});
            out_path = args[i + 1];
            i += 2;
        } else if (std.mem.eql(u8, args[i], "--entry")) {
            if (i + 2 >= args.len) std.process.fatal("'--entry' needs a name and a path", .{});
            const name = args[i + 1];
            const path = args[i + 2];
            const bytes = Io.Dir.cwd().readFileAlloc(io, path, arena, .limited(max_input_bytes)) catch |err| {
                std.process.fatal("cannot read '{s}': {t}", .{ path, err });
            };
            var digest: [std.crypto.hash.sha2.Sha256.digest_length]u8 = undefined;
            std.crypto.hash.sha2.Sha256.hash(bytes, &digest, .{});
            // The two-space separator is `sha256sum`'s text mode, which is what
            // `sha256sum -c SHA256SUMS` expects on the operator's machine.
            try line_buffer.writer.print("{s}  {s}\n", .{ std.fmt.bytesToHex(digest, .lower), name });
            i += 3;
        } else {
            std.process.fatal("unknown flag '{s}'", .{args[i]});
        }
    }

    try writeFileWithMode(io, Io.Dir.cwd(), required(out_path, "--out"), line_buffer.written(), 0o644);
}

fn required(value: ?[]const u8, flag: []const u8) []const u8 {
    return value orelse std.process.fatal("'{s}' is required", .{flag});
}

fn copyInto(arena: Allocator, io: Io, out: Io.Dir, file: PayloadFile, source: []const u8) !void {
    const bytes = Io.Dir.cwd().readFileAlloc(io, source, arena, .limited(max_input_bytes)) catch |err| {
        std.process.fatal("cannot read '{s}': {t}", .{ source, err });
    };
    try writeInto(io, out, file, bytes);
}

fn writeInto(io: Io, out: Io.Dir, file: PayloadFile, bytes: []const u8) !void {
    try writeFileWithMode(io, out, file.name, bytes, file.mode);
}

fn writeFileWithMode(
    io: Io,
    dir: Io.Dir,
    sub_path: []const u8,
    bytes: []const u8,
    mode: std.posix.mode_t,
) !void {
    var handle = dir.createFile(io, sub_path, .{}) catch |err| {
        std.process.fatal("cannot create '{s}': {t}", .{ sub_path, err });
    };
    defer handle.close(io);
    handle.writeStreamingAll(io, bytes) catch |err| {
        std.process.fatal("cannot write '{s}': {t}", .{ sub_path, err });
    };
    // After the write, not through the creation mode: `open(2)` masks the
    // creation mode with the process umask, and the release modes are fixed.
    handle.setPermissions(io, .fromMode(mode)) catch |err| {
        std.process.fatal("cannot set the mode of '{s}': {t}", .{ sub_path, err });
    };
}

/// `THIRD-PARTY-NOTICES`: the inventory's entries, in order, each with its
/// selection note and the full text of its licence.
fn renderNotices(arena: Allocator, io: Io, dir_path: []const u8) ![]const u8 {
    var dir = Io.Dir.cwd().openDir(io, dir_path, .{}) catch |err| {
        std.process.fatal("cannot open --licenses directory '{s}': {t}", .{ dir_path, err });
    };
    defer dir.close(io);

    const source = dir.readFileAllocOptions(
        io,
        "inventory.zon",
        arena,
        .limited(max_input_bytes),
        .of(u8),
        0,
    ) catch |err| {
        std.process.fatal("cannot read '{s}/inventory.zon': {t}", .{ dir_path, err });
    };

    const components = try parseInventory(arena, source);
    if (components.len == 0) {
        std.process.fatal("'{s}/inventory.zon' lists no components", .{dir_path});
    }

    // The preamble is a reviewed file rather than a literal here so that one
    // text states the artifact scope and the drift guards in
    // src/licenses_drift_test.zig can assert against it.
    const preamble = dir.readFileAlloc(io, "preamble.txt", arena, .limited(max_input_bytes)) catch |err| {
        std.process.fatal("cannot read '{s}/preamble.txt': {t}", .{ dir_path, err });
    };
    if (std.mem.trim(u8, preamble, " \t\r\n").len == 0) {
        std.process.fatal("'{s}/preamble.txt' is empty", .{dir_path});
    }

    var sink: std.Io.Writer.Allocating = try .initCapacity(arena, 64 << 10);
    const w = &sink.writer;
    try w.writeAll(preamble);
    if (preamble[preamble.len - 1] != '\n') try w.writeByte('\n');
    try w.writeByte('\n');

    for (components) |component| {
        const text = dir.readFileAlloc(io, component.file, arena, .limited(max_input_bytes)) catch |err| {
            std.process.fatal("cannot read '{s}/{s}': {t}", .{ dir_path, component.file, err });
        };
        try w.splatByteAll('=', 76);
        try w.print("\n{s}\n", .{component.component});
        try w.splatByteAll('=', 76);
        try w.print("\n\nVersion: {s}\n\n{s}\n\n{s}", .{ component.version, component.note, text });
        if (text.len != 0 and text[text.len - 1] != '\n') try w.writeByte('\n');
        try w.writeByte('\n');
    }

    return sink.written();
}

/// The inventory is a tuple of components, in the order they appear in the
/// notices file.
fn parseInventory(arena: Allocator, source: [:0]const u8) ![]const Component {
    var diagnostics: std.zon.parse.Diagnostics = .{};
    return std.zon.parse.fromSliceAlloc(
        []const Component,
        arena,
        source,
        &diagnostics,
        .{ .free_on_error = false },
    ) catch |err| switch (err) {
        error.OutOfMemory => return error.OutOfMemory,
        error.ParseZon => std.process.fatal("licenses/inventory.zon:\n{f}", .{&diagnostics}),
    };
}