class StructuredNode {
    constructor(json) {
        if (this.constructor === StructuredNode) {
            throw new TypeError('Cannot instantiate object of abstract type StructuredNode!')
        }

        this.json = json
        this.changes = {}
        this.definition = StructuredNode.classes[this.constructor.name]
        this.hooks = []
        this.deleted = false
        this.__name__ = this.constructor.name.toLowerCase()
    }

    check(name, type, new_value) {
        return true
    }

    _link_property(name, elm) {
        const relation = this.definition.rels[name]

        if (!relation) {
            throw new ApiError(`Cannot find realation ${name} of object ${this.constructor.name}!`, 404, {obj: this, elm: elm})
        }
        const type = StructuredNode.classes[relation.target].klass

        if (typeof elm == "string") {
            elm = type.by_id(elm)
        }
        if (elm instanceof type) {
            if (!elm.exists() || !this.exists()) {
                throw new ApiError("Cannot connect object before it exists on the backend!")
            }

            // make results available immediately
            if (relation.cardinality.endsWith('OrMore')) {
                if (!this.json[name].contains(elm)) {
                    this.json[name].push(elm)
                }
            } else {
                this.json[name] = elm
            }

            return Api.post(`/${this.__name__}/${this.json.uid}/${name}/${elm.json.uid}`).then(json => {
                this.json = json
                this.update('link')
                return this
            })
        }
    }

    _unlink_property(name, type, elm) {
        return Api.delete(`/${this.__name__}/${this.json.uid}/${name}/${elm.json.uid}`).then(json => {
            this.json = json
            this.update('link')
            return this
        })
    }

    static by_id(uid) {
        return Api.get('/' + this.name.toLowerCase() + '/' + uid).then(x => new this(x))
    }

    static find(attributes, settings) {

    }

    save() {
        if (this.deleted) {
            throw new ApiError("Cannot save deleted object!", {obj: this})
        }

        if (this.json.uid) {
            return Api.put(`/${this.__name__}/${this.json.uid}`, this.changes).then(json => {
                this.json = json
                this.changes = {}
                this.update('save')
                return this
            })
        } else {
            return Api.post('/' + this.__name__, this.json).then(json => {
                this.json = json
                this.changes = {}
                this.update('created')
                return this
            })
        }
    }

    delete() {
        if (!this.exists()) {
            throw new ApiError("Cannot delete object that does not exist yet!", {obj: this})
        }
        this.deleted = true
        Api.delete(`/${this.__name__}/${this.json.uid}`).then(r => {
            this.update('deleted')
            return this
        })
    }

    exists() {
        return !this.deleted && !!this.json.uid
    }

    onupdate(callback) {
        this.hooks.push(callback)
    }

    update(event) {
        this.hooks.forEach(cb => {
            try {
                cb(this, event)
            } catch (e) {
                console.error(`Error while running update on ${this.constructor.name} update function ${cb}: ${e}`)
                console.error(cb, event, e)
            }
        })
    }

    static registerClassDefinition(klass, props, rels) {
        console.log(klass, props, rels)
        StructuredNode.classes[klass.name] = {klass, props, rels}
    }

}
StructuredNode.classes = {}

class Api {
    static set_auth(token) {
        Api.token = token;
    }

    static get(url) {
        return fetch('/api' + url, {headers: Api.headers()}).then(r => {
            if (r.ok) {
                return r.json()
            } else {
                // evaluate response and raise error
                return ApiError.fromResponse(r)
            }
        })
    }
    static post(url, body="") {
        return fetch('/api' + url, {headers: Api.headers(), body: JSON.stringify(body), method: 'POST'}).then(r => {
            if (r.ok) {
                return r.json()
            } else {
                // evaluate response and raise error
                return ApiError.fromResponse(r)
            }
        })
    }
    static put(url, body) {
        return fetch('/api' + url, {headers: Api.headers(), body: JSON.stringify(body), method: 'PUT'}).then(r => {
            if (r.ok) {
                return r.json()
            } else {
                // evaluate response and raise error
                return ApiError.fromResponse(r)
            }
        })
    }
    static delete(url) {
        return fetch('/api' + url, {headers: Api.headers(), method: 'DELETE'}).then(r => {
            if (r.ok) {
                return r
            } else {
                // evaluate response and raise error
                return ApiError.fromResponse(r)
            }
        })
    }

    static headers() {
        return {
            'Content-Type': 'application/json',
            // 'Authorization': 'Bearer ' + Api.token
        }
    }
}

class ApiError {
    constructor(msg, code, data) {
        this.msg = msg
        this.code = code
        this.data = data
    }

    static fromResponse(r) {
        if (r.headers.get('Content-Type') === 'application/json') {
            return r.json().then(json => {
                throw new ApiError(json.msg, r.status, json.data)
            })
        } else {
            return r.text().then(text => {
                throw new ApiError(text, r.status)
            })
        }
    }
}