// Portable row payloads: translate cross-site references so a reference row means
// the same thing on both instances.
//
//   * The local primary key is dropped (reassigned per site).
//   * The stable identity `_ss_row_uuid` travels as `__uuid` (the match key).
//   * A foreign key into a managed/starter table is replaced with the referenced
//     row's `_ss_row_uuid` under `<field>__uuid`; on apply it is resolved back to
//     the local id. An FK into a USER-mode table (no cross-site identity) is nulled
//     with a warning -- reference identity only exists for managed/starter tables.
//   * File-typed fields travel as a CONTENT-ADDRESSED placeholder under
//     `<field>__file` ({hash, filename, mime, min_role_read}); the row engine
//     fetches the bytes by hash and materializes a local file.
//   * Other infra columns (any other "_"-prefixed field, e.g. dev-deploy's
//     _dd_row_uuid) are per-instance bookkeeping and never travel.
//
// This module is the single source of truth for the portable key format.

const File = require("@saltcorn/data/models/file");

const { ROW_UUID_FIELD, findIdByRowUuid, getRowUuidById } = require("./rowIdentity");
const { isInfraName, isSyncedMode } = require("./constants");
const { hashFileContents } = require("./common/fileStore");


// The row identity travels under PORTABLE_UUID_KEY; FK columns as
// "<field>__uuid" (same suffix); File fields as "<field>__file".
const UUID_SUFFIX       = "__uuid";
const PORTABLE_UUID_KEY = UUID_SUFFIX;
const FILE_SUFFIX       = "__file";

const isFkUuidKey = (key) => key !== PORTABLE_UUID_KEY && key.endsWith(UUID_SUFFIX);
const isFileKey   = (key) => key.endsWith(FILE_SUFFIX);
const fileFieldOf = (key) => key.slice(0, -FILE_SUFFIX.length);


// Row -> portable. `modeOf(tableName)` yields the local data mode of a table so we
// know whether an FK target participates in cross-site identity.
const rowToPortable = async (row, table, modeOf) => {
    const portable = {};
    const warnings = [];
    const pk = table.pk_name;
    for (const field of table.getFields()) {
        const name = field.name;
        if (name === pk) {
            continue;
        }
        if (name === ROW_UUID_FIELD) {
            portable[PORTABLE_UUID_KEY] = row[name];
            continue;
        }
        if (isInfraName(name)) {
            continue;
        }
        const value = row[name];
        if (field.type === "File") {
            // Ship a CONTENT-ADDRESSED placeholder: the file's sha256 hash plus the
            // metadata needed to recreate it. The bytes are fetched separately by the
            // target from GET /api/file/:hash. Nulled (with a warning) if the file is
            // missing on disk.
            if (value === null || value === undefined || value === "") {
                portable[`${name}${FILE_SUFFIX}`] = null;
            } else {
                try {
                    const file = await File.findOne(value);
                    if (file) {
                        portable[`${name}${FILE_SUFFIX}`] = {
                            hash:          await hashFileContents(file),
                            filename:      file.filename,
                            mime:          file.mimetype,
                            min_role_read: file.min_role_read
                        };
                    } else {
                        warnings.push(`file field ${table.name}.${name} value "${value}" not found on disk; nulled`);
                        portable[`${name}${FILE_SUFFIX}`] = null;
                    }
                } catch (e) {
                    warnings.push(`file field ${table.name}.${name}: ${e.message}`);
                    portable[`${name}${FILE_SUFFIX}`] = null;
                }
            }
            continue;
        }
        if (field.is_fkey) {
            const reftable = field.reftable_name;
            if (reftable && isSyncedMode(modeOf(reftable))) {
                if (value === null || value === undefined) {
                    portable[`${name}${UUID_SUFFIX}`] = null;
                } else {
                    const refUuid = await getRowUuidById(reftable, value);
                    if (!refUuid) {
                        warnings.push(`FK ${table.name}.${name} -> ${reftable} could not resolve a row uuid`);
                    }
                    portable[`${name}${UUID_SUFFIX}`] = refUuid || null;
                }
            } else {
                if (value !== null && value !== undefined) {
                    warnings.push(`FK ${table.name}.${name} into non-synced table ${reftable || "?"} nulled`);
                }
                portable[name] = null;
            }
            continue;
        }
        portable[name] = value;
    }
    return { portable, warnings };
};


// Portable -> row (local ids resolved). Returns { row, warnings }. The returned row
// includes _ss_row_uuid so a plain insertRow/updateRow carries the identity.
// `resolveRef(reftable, uuid)` maps a referenced row's uuid to its local pk (or
// null); the row engine passes a cached resolver, the default queries per call.
// Infra keys from a peer (other than the identity) are never written.
const portableToRow = async (portable, table, resolveRef = findIdByRowUuid) => {
    const row = {};
    const warnings = [];
    for (const key of Object.keys(portable)) {
        if (key === PORTABLE_UUID_KEY) {
            row[ROW_UUID_FIELD] = portable[key];
            continue;
        }
        if (isFileKey(key)) {
            // File placeholders are materialized by the row engine (needs the peer
            // transport to fetch bytes); skip here.
            continue;
        }
        if (isFkUuidKey(key)) {
            const fieldName = key.slice(0, -UUID_SUFFIX.length);
            const field = table.getField(fieldName);
            if (!field) {
                continue;
            }
            const refUuid = portable[key];
            if (refUuid === null || refUuid === undefined) {
                row[fieldName] = null;
                continue;
            }
            const localId = await resolveRef(field.reftable_name, refUuid);
            if (localId === null) {
                warnings.push(`FK ${table.name}.${fieldName} unresolved (referenced row not synced yet); set null`);
                row[fieldName] = null;
            } else {
                row[fieldName] = localId;
            }
            continue;
        }
        if (isInfraName(key)) {
            continue;
        }
        row[key] = portable[key];
    }
    return { row, warnings };
};


module.exports = {
    PORTABLE_UUID_KEY,
    isFileKey,
    fileFieldOf,
    rowToPortable,
    portableToRow
};