//! Generate skill.json from template by substituting Lambda ARN
//!
//! Usage: gen-skill-json <deploy-output.json> <skill.template.json>
//! Outputs the generated skill.json to stdout.

const std = @import("std");

pub fn main() !void {
    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
    defer _ = gpa.deinit();
    const allocator = gpa.allocator();

    const args = try std.process.argsAlloc(allocator);
    defer std.process.argsFree(allocator, args);

    if (args.len != 3) {
        std.debug.print("Usage: {s} <deploy-output.json> <skill.template.json>\n", .{args[0]});
        std.process.exit(1);
    }

    const deploy_output_path = args[1];
    const template_path = args[2];

    // Read deploy output JSON
    const deploy_output = try readFile(allocator, deploy_output_path);
    defer allocator.free(deploy_output);

    // Parse to extract ARN
    const parsed = try std.json.parseFromSlice(std.json.Value, allocator, deploy_output, .{});
    defer parsed.deinit();

    const arn = parsed.value.object.get("arn") orelse {
        std.debug.print("Error: deploy output missing 'arn' field\n", .{});
        std.process.exit(1);
    };

    const arn_str = switch (arn) {
        .string => |s| s,
        else => {
            std.debug.print("Error: 'arn' field is not a string\n", .{});
            std.process.exit(1);
        },
    };

    // Read template
    const template = try readFile(allocator, template_path);
    defer allocator.free(template);

    // Replace placeholder with ARN
    const result = try std.mem.replaceOwned(u8, allocator, template, "{{LAMBDA_ARN}}", arn_str);
    defer allocator.free(result);

    // Write to stdout
    const stdout = std.fs.File.stdout();
    try stdout.writeAll(result);
}

fn readFile(allocator: std.mem.Allocator, path: []const u8) ![]u8 {
    const file = try std.fs.cwd().openFile(path, .{});
    defer file.close();

    return try file.readToEndAlloc(allocator, 1024 * 1024);
}