//! Subcommand dispatch for the `panto` CLI.
//!
//! Routes argv[1] to one of:
//!   - `lua`        — drop into the embedded standalone Lua interpreter
//!                    (panto's `lua.c` build), with luarocks's runtime
//!                    bootstrap completed first so `require("luarocks.*")`
//!                    and the configured rocks tree work the same as in
//!                    the agent process.
//!   - `bootstrap`  — run the luarocks runtime bootstrap pipeline only;
//!                    exit before entering any agent loop. Lets users
//!                    do first-run setup on a fresh machine without
//!                    starting a chat session.
//!   - anything else (or absent) — fall through to the agent REPL.
//!
//! Both `lua` and `bootstrap` end up calling `luarocks_runtime.bootstrap`
//! before doing their thing. The agent path does the same; the only
//! difference is whether the agent loop runs afterward.

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

const lua_bridge = @import("lua_bridge.zig");
const luarocks_runtime = @import("luarocks_runtime.zig");
const self_exe = @import("self_exe.zig");

const c = lua_bridge.c;

pub const Action = enum {
    /// Continue with the default agent REPL.
    agent,
    /// Bootstrap is already done; the dispatcher consumed the subcommand.
    /// `main` should exit immediately.
    done,
};

/// Inspect `argv[1]`, run the appropriate subcommand, and return what
/// the caller should do next. On `.agent`, the dispatcher leaves argv
/// untouched and `main` continues as before. On `.done`, the caller
/// must return promptly (the subcommand has already produced output).
///
/// `panto_executable_path` is the absolute path of the running panto
/// binary, used both to wire up the embedded luarocks `LUA` variable
/// and to `exec` ourselves where needed.
pub fn dispatch(
    allocator: Allocator,
    io: Io,
    environ_map: *const std.process.Environ.Map,
    args: std.process.Args,
    panto_executable_path: []const u8,
) !Action {
    var it = args.iterate();
    defer it.deinit();
    _ = it.next(); // argv[0]

    const sub = it.next() orelse return .agent;

    if (std.mem.eql(u8, sub, "lua")) {
        try runLuaSubcommand(allocator, io, environ_map, args, panto_executable_path);
        return .done;
    }
    if (std.mem.eql(u8, sub, "bootstrap")) {
        var force = false;
        while (it.next()) |flag| {
            if (std.mem.eql(u8, flag, "--force")) {
                force = true;
            } else {
                std.log.err("panto bootstrap: unknown flag '{s}'", .{flag});
                return error.UnknownFlag;
            }
        }
        try runBootstrapSubcommand(allocator, io, environ_map, panto_executable_path, .{ .force = force });
        return .done;
    }
    return .agent;
}

pub const BootstrapOptions = struct {
    /// Wipe the per-Lua-version tree before reinstalling everything.
    /// Surfaced as `panto bootstrap --force`. Equivalent to deleting
    /// `$PANTO_HOME/rocks/lua-X.Y.Z/` by hand and then running
    /// `panto bootstrap`.
    force: bool = false,
};

// ---------------------------------------------------------------------------
// `panto lua`
// ---------------------------------------------------------------------------

extern "c" fn panto_lua_pmain(L: *c.lua_State, argc: c_int, argv: [*]?[*:0]u8) c_int;

/// Drop into the embedded Lua standalone interpreter, with the
/// luarocks runtime bootstrap completed so `require("luarocks.*")`
/// and rocks installed under `$PANTO_HOME` are visible.
///
/// argv is rewritten so the interpreter sees `lua [...args]` rather
/// than `panto lua [...args]` — matching upstream behavior. The first
/// argument visible to `pmain` is the program name; this matters for
/// `arg[0]` and error reporting.
fn runLuaSubcommand(
    allocator: Allocator,
    io: Io,
    environ_map: *const std.process.Environ.Map,
    args: std.process.Args,
    panto_executable_path: []const u8,
) !void {
    // Build a fresh lua_State that we own, configure it like luarocks
    // expects, then hand it to `pmain`.
    const L = c.luaL_newstate() orelse return error.LuaInitFailed;
    defer c.lua_close(L);

    // Run bootstrap against this state. This installs the embedded
    // searcher, configures package.path/cpath, and stages on-disk
    // resources. We deliberately do NOT call `luaL_openlibs` here —
    // `pmain` does that itself, and we want exactly the upstream
    // ordering for everything that runs inside the REPL.
    //
    // The searcher install only requires `package.searchers` to be
    // present; the stock libs ship it. We open libs once here just
    // to satisfy that, then pmain's own `luaL_openlibs` is idempotent.
    c.luaL_openlibs(L);
    const rt = try luarocks_runtime.bootstrap(
        allocator,
        io,
        environ_map,
        L,
        panto_executable_path,
    );
    defer rt.deinit();

    // Re-create the argv the standalone interpreter expects. argv[0]
    // is the program name; argv[1..] are the user's args.
    var raw_args = args.iterate();
    defer raw_args.deinit();
    _ = raw_args.next(); // panto
    _ = raw_args.next(); // lua

    var argv_list: std.array_list.Managed([:0]u8) = .init(allocator);
    defer {
        for (argv_list.items) |s| allocator.free(s);
        argv_list.deinit();
    }

    // Program name first.
    try argv_list.append(try allocator.dupeZ(u8, "lua"));
    while (raw_args.next()) |a| {
        try argv_list.append(try allocator.dupeZ(u8, a));
    }

    // Build a `[*]?[*:0]u8` argv pointer array. lua.c expects a
    // NULL-terminated array (it uses `argv[i]` indexed access through
    // argc; the trailing NULL is conventional for C `main`).
    var argv_c: std.array_list.Managed(?[*:0]u8) = .init(allocator);
    defer argv_c.deinit();
    for (argv_list.items) |s| {
        try argv_c.append(s.ptr);
    }
    try argv_c.append(null);

    const exit_code = panto_lua_pmain(L, @intCast(argv_list.items.len), argv_c.items.ptr);
    if (exit_code != 0) std.process.exit(@intCast(exit_code));
}

// ---------------------------------------------------------------------------
// `panto bootstrap`
// ---------------------------------------------------------------------------

/// Run the luarocks bootstrap and exit. Useful for first-run setup on
/// a clean machine (downloads + compiles batteries, stages headers,
/// materializes config) and for CI/scripted installs.
///
/// Idempotent: subsequent invocations no-op fast, unless `force` was
/// passed — then the entire per-Lua-version tree is wiped before the
/// regular bootstrap pipeline runs.
fn runBootstrapSubcommand(
    allocator: Allocator,
    io: Io,
    environ_map: *const std.process.Environ.Map,
    panto_executable_path: []const u8,
    opts: BootstrapOptions,
) !void {
    if (opts.force) {
        try luarocks_runtime.wipeTree(allocator, io, environ_map);
    }

    const L = c.luaL_newstate() orelse return error.LuaInitFailed;
    defer c.lua_close(L);
    c.luaL_openlibs(L);

    const rt = try luarocks_runtime.bootstrap(
        allocator,
        io,
        environ_map,
        L,
        panto_executable_path,
    );
    defer rt.deinit();

    // Pleasant single-line confirmation. The interesting bits (rock
    // installs etc.) print their own progress.
    std.log.info(
        "panto bootstrap: tree ready at {s}",
        .{rt.layout.tree},
    );
}

// ---------------------------------------------------------------------------
// `panto lua` argv plumbing — sketched against the older Args API for
// reference (kept here so the design notes survive the implementation).
// ---------------------------------------------------------------------------
//
// Because we own the `lua_State` end-to-end, the subcommand can also
// expose extra panto-specific globals to user code (e.g. surface the
// resolved $PANTO_HOME) without disturbing upstream `lua.c` behavior.
// Step out of scope for the current makeover; add when needed.

// ---------------------------------------------------------------------------
// Tests
// ---------------------------------------------------------------------------

const testing = std.testing;

// Note: `dispatch` reads from the process's real argv, which isn't
// controllable from a unit test. The behavior is exercised by
// integration runs of the panto binary. We test the smaller pieces.
//
// Suppress dead-code warnings for `self_exe` (it's used by main, not
// by tests in this module).
test {
    _ = self_exe;
}