import { createHash } from "node:crypto";
export const migrationObjectId = (executionId, port, logicalKey) => `obj:migration:${createHash("sha256")
    .update(JSON.stringify([executionId, port, logicalKey]))
    .digest("hex")}`;
/** No ordinary RuntimeContext or network/database clients are supplied here.
 * Process isolation belongs to the host, not this convenience API. */
export const createMigrationContext = (input) => {
    if (input.schemaVersion !== 1 ||
        !input.executionId ||
        new Set(input.ports.map((entry) => entry.name)).size !== input.ports.length)
        throw new Error("Invalid migration input");
    const output = {
        schemaVersion: 1,
        executionId: input.executionId,
        writes: [],
        creates: [],
        edgeReplacements: [],
    };
    const port = (name, access) => {
        const selected = input.ports.find((entry) => entry.name === name);
        if (!selected?.access.includes(access) || (selected.view === "old" && access !== "read"))
            throw new Error(`Migration port ${name} does not grant ${access}`);
        return selected;
    };
    const context = {
        enumerate(name) {
            const selected = port(name, "read"), states = structuredClone(selected.states ?? []);
            if (selected.view === "new" && Object.hasOwn(selected, "defaultValue"))
                for (const helper of output.creates) {
                    if (input.ports.find((entry) => entry.name === helper.port)?.atomId === selected.attachedAtomId &&
                        !states.some((entry) => entry.objectId === helper.objectId))
                        states.push({ objectId: helper.objectId, value: structuredClone(selected.defaultValue) });
                }
            if (selected.view === "new")
                for (const write of output.writes) {
                    if (input.ports.find((entry) => entry.name === write.port)?.binding !== selected.binding)
                        continue;
                    const existing = states.findIndex((entry) => entry.objectId === write.objectId), entry = { objectId: write.objectId, value: structuredClone(write.value) };
                    if (existing < 0)
                        states.push(entry);
                    else
                        states[existing] = entry;
                }
            return states.sort((a, b) => (a.objectId < b.objectId ? -1 : a.objectId > b.objectId ? 1 : 0));
        },
        read(name, objectId) {
            return context.enumerate(name).find((entry) => entry.objectId === objectId)?.value;
        },
        write(name, objectId, value) {
            port(name, "write");
            const previous = output.writes.findIndex((entry) => entry.port === name && entry.objectId === objectId);
            const entry = { port: name, objectId, value: structuredClone(value) };
            if (previous < 0)
                output.writes.push(entry);
            else
                output.writes[previous] = entry;
        },
        create(name, logicalKey) {
            port(name, "create");
            if (!logicalKey || logicalKey.length > 1024)
                throw new Error("Migration creation requires a bounded stable logical key");
            const objectId = migrationObjectId(input.executionId, name, logicalKey);
            if (!output.creates.some((entry) => entry.objectId === objectId))
                output.creates.push({ port: name, logicalKey, objectId });
            return objectId;
        },
        edges(name) {
            const selected = port(name, "read");
            const replacement = selected.view === "new"
                ? output.edgeReplacements.find((entry) => input.ports.find((candidate) => candidate.name === entry.port)?.binding === selected.binding)
                : undefined;
            return structuredClone(replacement?.edges ?? selected.edges ?? []);
        },
        replaceEdges(name, edges) {
            port(name, "edge");
            const previous = output.edgeReplacements.findIndex((entry) => entry.port === name);
            const entry = { port: name, edges: structuredClone(edges) };
            if (previous < 0)
                output.edgeReplacements.push(entry);
            else
                output.edgeReplacements[previous] = entry;
        },
    };
    return { context, result: () => structuredClone(output) };
};
/** Entrypoint for an immutable package's dedicated bin/migrate executable.
 * stdout is protocol-only; send diagnostics to stderr. The host independently
 * validates every write, helper identity, contract, and completion receipt. */
export const serveMigration = async (exports) => {
    const chunks = [];
    let bytes = 0;
    for await (const chunk of process.stdin) {
        bytes += chunk.length;
        if (bytes > 16 * 1024 * 1024)
            throw new Error("Migration input exceeds 16 MiB");
        chunks.push(Buffer.from(chunk));
    }
    const input = JSON.parse(Buffer.concat(chunks).toString("utf8"));
    const implementation = Object.hasOwn(exports, input.exportId) ? exports[input.exportId] : undefined;
    if (!implementation)
        throw new Error("Unknown migration export");
    const execution = createMigrationContext(input);
    await implementation(execution.context);
    const result = JSON.stringify(execution.result());
    if (Buffer.byteLength(result) > 16 * 1024 * 1024)
        throw new Error("Migration output exceeds 16 MiB");
    process.stdout.write(`${result}\n`);
};