salix/services/loopback/common/models/loggable.js

const pick = require('object.pick');
const LoopBackContext = require('loopback-context');

module.exports = function(Self) {
    Self.setup = function() {
        Self.super_.setup.call(this);
    };

    Self.observe('after save', async function(ctx) {
        const loopBackContext = LoopBackContext.getCurrentContext();
        await logInModel(ctx, loopBackContext);
    });

    Self.observe('before save', async function(ctx) {
        let oldInstance;
        let oldInstanceFk;
        let newInstance;
        if (ctx.data) {
            oldInstanceFk = pick(ctx.currentInstance, Object.keys(ctx.data));
            newInstance = await fkToValue(ctx.data, ctx);
            oldInstance = await fkToValue(oldInstanceFk, ctx);
        }
        if (ctx.isNewInstance) {
            newInstance = await fkToValue(ctx.instance.__data, ctx);
        }
        ctx.hookState.oldInstance = oldInstance;
        ctx.hookState.newInstance = newInstance;
    });

/*     Self.observe('before delete', async function(ctx, next) {
        let oldInstance;
        if (ctx.instance) {
            oldInstance = await fkToValue(ctx.data, ctx);
        }
        await logInModel(ctx);

        next();
    });

    Self.observe('after delete', async function(ctx, next) {
        let oldInstance;
        if (ctx.instance) {
            oldInstance = await fkToValue(ctx.data, ctx);
        }
        await logInModel(ctx);

        next();
    }); 
*/


    async function fkToValue(instance, ctx) {
        let result = {};
        for (let key in instance) {
            if (key == 'id') continue;
            let val = instance[key];
            if (val === undefined) continue;
            for (let key1 in ctx.Model.relations) {
                let val1 = ctx.Model.relations[key1];
                if (val1.keyFrom == key) {
                    let recordSet = await val1.modelTo.findById(val);
                    val = recordSet.name; // FIXME preparar todos los modelos con campo name
                    break;
                }
            }
            result[key] = val;
        }
        return result;
    }

    async function logInModel(ctx, loopBackContext) {

        let definition = ctx.Model.definition;
        let primaryKey;
        for (let property in definition.properties) {
            if (definition.properties[property].id) {
                primaryKey = property;
                break;
            }
        }
        if (!primaryKey) throw new Error('Primary key not found');
        let originId;

        if (definition.settings.log.relation) {
            // RELATIONS LOG
            primaryKey = ctx.Model.relations[definition.settings.log.relation].keyFrom;

            if(ctx.where && ctx.where[primaryKey])
                originId = ctx.where[primaryKey]
            else
                originId = ctx.instance[primaryKey];
        } else {
            if (ctx.instance) {
                originId = ctx.instance.id;
            } else {
                originId = ctx.currentInstance.id;
            }
        }

        // This adds the originDescription field if it doesnt exists in the instances

        let originDescription = definition.settings.log.originDescription;

        if (originDescription && (!ctx.instance || !ctx.instance[originDescription]))
            await Self.modelBuilder.models[definition.name].findById()

        if (ctx.hookState.oldInstance && !ctx.hookState.oldInstance[originDescription]){
            ctx.hookState.oldInstance[originDescription] = ctx.instance[originDescription];
            ctx.hookState.newInstance[originDescription] = ctx.instance[originDescription];
        }

        // This put some order in the intances putting the originDescription in first place

        let oldInstance = {};
        if (ctx.hookState.oldInstance) {
            oldInstance[originDescription] = ctx.hookState.oldInstance[originDescription];
            delete ctx.hookState.oldInstance[originDescription];
            Object.assign(oldInstance, ctx.hookState.oldInstance);
        }

        let newInstance = {};
        if (ctx.hookState.newInstance) {
            newInstance[originDescription] = ctx.hookState.newInstance[originDescription];
            delete ctx.hookState.newInstance[originDescription];
            Object.assign(newInstance, ctx.hookState.newInstance)
        }

        let action = setActionType(ctx);
        let userFk = loopBackContext.active.accessToken.userId;

        let logRecord = {
            originFk: originId,
            userFk: userFk,
            model: ctx.Model.definition.name,
            action: action,
            oldInstance: oldInstance,
            newInstance: newInstance
        };


        let logModel = definition.settings.log.model
        await Self.modelBuilder.models[logModel].create(logRecord);
    }

    function setActionType(ctx) {
        let oldInstance = ctx.hookState.oldInstance;
        let newInstance = ctx.hookState.newInstance;

        if  (oldInstance && newInstance) {
            return 'update';
        } else if (!oldInstance && newInstance) {
            return 'insert';
        }
    }
};