import Database from '../service/Database.ts'
import ModelResultOperator from './ModelResultOperator.ts'
import ObjectResultOperator from '../builder/type/result/ObjectResultOperator.ts'
import {Builder} from '../builder/Builder.ts'
import {FieldSet, FieldValueObject, QuerySource} from '../builder/types.ts'
import {make} from '../../../di/src/global.ts'
import {QueryRow, ModelKey} from '../db/types.ts'
import {get_fields_meta, ModelField, set_model_fields_meta} from './Field.ts'
import {Collection} from '../../../lib/src/collection/Collection.ts'
import {logger} from '../../../lib/src/service/logging/global.ts'
import {QueryFilter} from './filter.ts'
import {BehaviorSubject} from '../../../lib/src/support/BehaviorSubject.ts'
import {Scope} from '../builder/Scope.ts'
import {JSONState, Rehydratable} from '../../../lib/src/support/Rehydratable.ts'

// TODO separate read/write connections
// TODO manual dirty flags

/**
 * Base class for database models.
 * @extends Builder
 */
export abstract class Model<T extends Model<T>> extends Builder<T> implements Rehydratable {
    /**
     * The name of the connection this model should run through.
     * @type string
     */
    protected static connection: string = 'default'

    /**
     * The name of the table this model is stored in.
     * @type string
     */
    protected static table: string

    /**
     * The name of the column that uniquely identifies this model.
     * @type string
     */
    protected static key: string

    /**
     * If false (default), the primary key will be excluded from INSERTs.
     */
    protected static populate_key_on_insert: boolean = false

    /**
     * Optionally, the timestamp field set on creation.
     * @type string
     */
    protected static readonly CREATED_AT: string | null = 'created_at'

    /**
     * Optionally, the timestamp field set op update.
     * @type string
     */
    protected static readonly UPDATED_AT: string | null = 'updated_at'

    /**
     * If true, the CREATED_AT and UPDATED_AT columns will be automatically set.
     * @type boolean
     */
    protected static timestamps = true

    /**
     * Array of global scopes to be applied to this model.
     * @type Scope[]
     */
    protected static global_scopes: Scope[] = []

    /**
     * Array of additional fields on the class that should
     * be included in the object serializations.
     * @type string[]
     */
    protected static appends: string[] = []

    /**
     * Array of fields on the class that should be excluded
     * from the object serializations.
     * @type string[]
     */
    protected static masks: string[] = []

    /**
     * The original query row that was fetched from the database.
     * @type QueryRow
     */
    protected _original?: QueryRow

    /**
     * Behavior subject that fires after the model is populated.
     */
    protected retrieved$ = new BehaviorSubject<Model<T>>()

    /**
     * Behavior subject that fires right before the model is saved.
     */
    protected saving$ = new BehaviorSubject<Model<T>>()

    /**
     * Behavior subject that fires right after the model is saved.
     */
    protected saved$ = new BehaviorSubject<Model<T>>()

    /**
     * Behavior subject that fires right before the model is updated.
     */
    protected updating$ = new BehaviorSubject<Model<T>>()

    /**
     * Behavior subject that fires right after the model is updated.
     */
    protected updated$ = new BehaviorSubject<Model<T>>()

    /**
     * Behavior subject that fires right before the model is inserted.
     */
    protected creating$ = new BehaviorSubject<Model<T>>()

    /**
     * Behavior subject that fires right after the model is inserted.
     */
    protected created$ = new BehaviorSubject<Model<T>>()

    /**
     * Behavior subject that fires right before the model is deleted.
     */
    protected deleting$ = new BehaviorSubject<Model<T>>()

    /**
     * Behavior subject that fires right after the model is deleted.
     */
    protected deleted$ = new BehaviorSubject<Model<T>>()

    /**
     * Get the model table name.
     * @return string
     */
    public static table_name() {
        return this.table
    }

    /**
     * Get the model connection name.
     * @return string
     */
    public static connection_name() {
        return this.connection
    }

    /**
     * Get the model connection.
     * @return Connection
     */
    public static get_connection() {
        return make(Database).connection(this.connection_name())
    }

    /**
     * Get a SELECT statement scoped to the model.
     * @param {...string[]} fields
     * @return Select
     */
    public static select(...fields: FieldSet[]) {
        return this.prototype.select(...fields)
    }

    /**
     * Get an UPDATE query scoped to this model.
     * @return Update
     */
    public static update() {
        return this.prototype.update()
    }

    /**
     * Get an INSERT query scoped to this model.
     * @return Insert
     */
    public static insert() {
        return this.prototype.insert()
    }

    /**
     * Get a DELETE query scoped to this model.
     * @return Delete
     */
    public static delete() {
        return this.prototype.delete()
    }

    /**
     * Get a TRUNCATE query scoped to this model.
     * @return Truncate
     */
    public static truncate() {
        return this.prototype.truncate()
    }

    /**
     * Get an UPDATE query scoped to this model.
     * @param {QuerySource} [target]
     * @param {string} [alias]
     * @return Update
     */
    public update(target?: QuerySource, alias?: string) {
        const constructor = (this.constructor as typeof Model)
        return super.update()
            .to(constructor.table_name())
            .with_scopes(constructor.global_scopes)
            .target_connection(constructor.get_connection())
            .target_operator(make(ModelResultOperator, constructor))
    }

    /**
     * Get a SELECT query scoped to this model.
     * @param {...FieldSet} fields
     */
    public select(...fields: FieldSet[]) {
        const constructor = (this.constructor as typeof Model)
        return super.select(...fields)
            .from(constructor.table_name())
            .with_scopes(constructor.global_scopes)
            .target_connection(constructor.get_connection())
            .target_operator(make(ModelResultOperator, constructor))
    }

    /**
     * Get an INSERT query scoped to this model.
     * @param {QuerySource} [target]
     * @param {string} [alias]
     * @return Insert
     */
    public insert(target?: QuerySource, alias?: string) {
        const constructor = (this.constructor as typeof Model)
        return super.insert()
            .into(constructor.table_name())
            .target_connection(constructor.get_connection())
            .target_operator(make(ModelResultOperator, constructor))
    }

    /**
     * Get a DELETE query scoped to this model.
     * @param {QuerySource} [target]
     * @param {string} [alias]
     * @return Delete
     */
    public delete(target?: QuerySource, alias?: string) {
        const constructor = (this.constructor as typeof Model)
        return super.delete()
            .from(constructor.table_name())
            .with_scopes(constructor.global_scopes)
            .target_connection(constructor.get_connection())
            .target_operator(make(ModelResultOperator, constructor))
    }

    /**
     * Get a TRUNCATE query scoped to this model.
     * @param {QuerySource} [target]
     * @param {string} [alias]
     * @return Truncate
     */
    public truncate(target?: QuerySource, alias?: string) {
        const constructor = (this.constructor as typeof Model)
        return super.truncate()
            .table(constructor.table_name())
            .target_connection(constructor.get_connection())
            .target_operator(make(ObjectResultOperator))
    }

    /**
     * Instantiate the model.
     * @param {object} [values] - optionally, row values to populate the model
     */
    constructor(
        values?: any
    ) {
        super()
        this.boot(values)
    }

    /**
     * Boot the model after creation.
     * @param [values]
     */
    public boot(values?: any) {
        if ( values ) {
            get_fields_meta(this).each(field_def => {
                // TODO special type casting
                // @ts-ignore
                this[field_def.model_key] = values[field_def.model_key]
            })
        }
    }

    /**
     * Given a query row, load the values into this model.
     * @param {QueryRow} row
     * @return Model
     */
    public assume_from_source(row: QueryRow) {
        this._original = row
        get_fields_meta(this).each(field_def => {
            // TODO special type casting
            // @ts-ignore
            this[field_def.model_key] = row[field_def.database_key]
        })
        this.retrieved$.next(this)
        return this
    }

    /**
     * If applicable get an object of normalized timestamps.
     * @return { updated_at?: Date, created_at?: Date }
     */
    public timestamps(): { updated_at?: Date, created_at?: Date } {
        const constructor = (this.constructor as typeof Model)
        const timestamps: { updated_at?: Date, created_at?: Date } = {}
        if ( constructor.timestamps ) {
            // @ts-ignore
            if ( constructor.CREATED_AT ) timestamps.created_at = this[constructor.CREATED_AT]

            // @ts-ignore
            if ( constructor.UPDATED_AT ) timestamps.updated_at = this[constructor.UPDATED_AT]
        }
        return timestamps
    }

    /**
     * Get a Select statement to pull back this model's database fields.
     * @param {...FieldSet} other_fields
     */
    public static model_select(...other_fields: FieldSet[]) {
        const fields = get_fields_meta(this.prototype).pluck('database_key').toArray()
        return this.select(...[...fields, ...other_fields])
    }

    /**
     * Find a collection of model instances given a filter.
     * @param {QueryFilter} filter
     * @return ResultCollection
     */
    public static async find(filter: QueryFilter = {}) {
        // @ts-ignore
        return await this.model_select().filter(filter).results()
    }

    /**
     * Find a single instance of the model given a filter.
     * @param {QueryFilter} filter
     * @return undefined | Model
     */
    public static async find_one(filter: QueryFilter = {}) {
        // @ts-ignore
        const result = await this.model_select().filter(filter).limit(1).results()
        return result.first()
    }

    /**
     * Find an instance of this model by primary key.
     * @param {ModelKey} key
     * @return undefined | Model
     */
    public static async find_by_key(key: ModelKey): Promise<undefined | typeof Model> {
        const result = await this.model_select()
            .where(this.qualified_key_name(), '=', key)
            .limit(1)
            .results()

        return result.first()
    }

    /**
     * Count the number of records of this model.
     * @return Promise<number>
     */
    public static async count(): Promise<number> {
        const result = this.model_select().results()
        return await result.count()
    }

    /**
     * Get a filter checking if a model field is dirty.
     * @private
     */
    protected get _is_dirty() {
        return (field_def: ModelField) => {
            // @ts-ignore
            return this[field_def.model_key] !== this._original[field_def.database_key]
        }
    }

    /**
     * Get a query row containing all database values from this model.
     * @return QueryRow
     */
    public to_row(): QueryRow {
        const row = {}
        this.field_defs()
            .each(field_def => {
                // @ts-ignore
                row[field_def.database_key] = this[field_def.model_key]
            })
        return row
    }

    /**
     * Get a query row containing the changed values from this model.
     * @return QueryRow
     */
    public dirty_to_row(): QueryRow {
        const row = {}
        this.field_defs()
            .filter(this._is_dirty)
            .each(field_def => {
                // TODO additional casting and serializing logic here
                // @ts-ignore
                row[field_def.database_key] = this[field_def.model_key]
            })
        return row
    }

    /**
     * Get a collection of field definitions that contains information
     * on which database fields correspond to which model fields, and
     * their types.
     * @return Collection<ModelField>
     */
    public static fields(): Collection<ModelField> {
        return get_fields_meta(this.prototype)
    }

    /**
     * Get a collection of field definitions that contains information
     * on which database fields correspond to which model fields, and
     * their types.
     * @return Collection<ModelField>
     */
    public field_defs(): Collection<ModelField> {
        return (this.constructor as typeof Model).fields()
    }

    /**
     * Sets the model field metadata to the specified collection of
     * model field definitions. You should rarely need to use this.
     * @param Collection<ModelField> fields
     */
    public static set_fields(fields: Collection<ModelField>) {
        set_model_fields_meta(this.prototype, fields)
    }

    /**
     * Get the original values of the model as they were retrieved from
     * the database. These are never updated when the model is modified.
     * @return QueryRow
     */
    public get_original_values() {
        return this._original
    }

    /**
     * Get an object with only the fields specified as arguments.
     * Note that this is NOT a QueryRow.
     * @param {...string} fields
     */
    public only(...fields: string[]) {
        const row = {}
        for ( const field of fields ) {
            // @ts-ignore
            row[field] = this[field]
        }
        return row
    }

    /**
     * Returns true if any of the defined fields have been modified from
     * the values that were originally fetched from the database.
     * @return boolean
     */
    public is_dirty() {
        return this.field_defs().some(this._is_dirty)
    }

    /**
     * Get an array of model field names that have been modified from
     * the values that were originally fetched from the database.
     * @return string[]
     */
    public dirty_fields() {
        return this.field_defs()
            .filter(this._is_dirty)
            .pluck('model_key')
            .toArray()
    }

    /**
     * Returns true if the model has an ID from, and therefore exists in,
     * the database backend.
     * @return boolean
     */
    public exists(): boolean {
        return !!this._original && !!this.key()
    }

    /**
     * Returns true if none of the defined fields have been modified from
     * the values that were originally fetched from the database.
     * @return boolean
     */
    public is_clean() {
        return !this.is_dirty()
    }

    /**
     * Returns true if the given field has been changed from the original
     * value fetched from the database.
     * @param string field
     * @return boolean
     */
    public was_changed(field: string) {
        // @ts-ignore
        return this.field_defs().pluck('model_key').includes(field) && this[field] !== this._original[field]
    }

    // has one
    // morph one
    // belongs to
    // morph to
    // has many
    // has many through
    // belongs to many
    // morph to many
    // morphed by many
    // is relation loaded
    // load relations
    // load missing relations
    // relations
    // with
    // relations_to_row

    // support for soft deletes!
    // force delete - for soft deleted models

    /**
     * Touch the UPDATED_AT/CREATED_AT timestamps where appropriate.
     */
    public touch() {
        const constructor = (this.constructor as typeof Model)
        if ( constructor.timestamps ) {
            if ( this.exists() && constructor.UPDATED_AT ) {
                // @ts-ignore
                this[constructor.UPDATED_AT] = new Date()
            }

            if ( constructor.CREATED_AT ) {
                // @ts-ignore
                this[constructor.CREATED_AT] = new Date()
            }
        }
        return this
    }

    /**
     * Get the result collection for all records of this model.
     * @return ResultCollection
     */
    public static all() {
        return this.model_select().results()
    }

    /**
     * Persist the model's record into the database. If we have a key,
     * update the record. Otherwise, perform an insert.
     * @param without_timestamps - if true, the UPDATED_AT/CREATED_AT timestamps will not be touched
     * @return Promise<Model>
     */
    public async save({ without_timestamps = false } = {}): Promise<Model<T>> {
        await this.saving$.next(this)
        const constructor = (this.constructor as typeof Model)

        // TODO timestamps
        if ( this.exists() && this.is_dirty() ) { // We're updating an existing record
            await this.updating$.next(this)

            if ( !without_timestamps && constructor.timestamps && constructor.UPDATED_AT ) {
                // @ts-ignore
                this[constructor.UPDATED_AT] = new Date()
            }

            const mutable = this.update()
                .data(this.dirty_to_row())
                .where(constructor.qualified_key_name(), '=', this.key())
                .returning(...this._loaded_database_fields())
                .target_operator(make(ObjectResultOperator))
                .results()

            const result = await mutable

            const modified_rows = await mutable.count()
            if ( modified_rows !== 1 ) {
                logger.warn(`Model update modified ${modified_rows} rows! (Key: ${constructor.qualified_key_name()})`)
            }

            const model = result.firstWhere(this.key_name(), '=', this.key())
            if ( model ) this.assume_from_source(model)
            await this.updated$.next(this)
        } else if ( !this.exists() ) { // We're inserting a new record
            await this.creating$.next(this)

            if ( !without_timestamps && constructor.timestamps && constructor.CREATED_AT ) {
                // @ts-ignore
                this[constructor.CREATED_AT] = new Date()
            }

            if ( constructor.timestamps && constructor.UPDATED_AT ) {
                // @ts-ignore
                this[constructor.UPDATED_AT] = new Date()
            }

            const insert_object: FieldValueObject = this._build_insert_field_object()
            const mutable = this.insert()
                .row(insert_object)
                .returning(this.key_name(), ...Object.keys(insert_object))
                .target_operator(make(ObjectResultOperator))
                .results()

            const result = await mutable

            const inserted_rows = await mutable.count()
            if ( inserted_rows !== 1 ) {
                logger.warn(`Model insert created ${inserted_rows} rows! (Key: ${constructor.qualified_key_name()})`)
            }

            const model = result.first()
            if ( model ) this.assume_from_source(model)
            await this.created$.next(this)
        }

        await this.saved$.next(this)
        return this
    }

    /**
     * Build a field value object from the values on this model to
     * populate an INSERT query.
     * @private
     * @return FieldValueObject
     */
    protected _build_insert_field_object(): FieldValueObject {
        let fields = this.field_defs()

        if ( !(this.constructor as typeof Model).populate_key_on_insert )
            fields = fields.whereNot('model_key', '=', this.key_name())

        const values = {}
        fields.each(field_def => {
            // @ts-ignore
            values[field_def.database_key] = this[field_def.model_key] ?? null
        })
        return values
    }

    /**
     * Return an array of fields that were loaded from the DB.
     * @private
     * @return string[]
     */
    protected _loaded_database_fields(): string[] {
        if ( typeof this._original === 'undefined' ) return []
        return Object.keys(this._original).map(String)
    }

    /**
     * Delete one or more records from this model's table by ID.
     * @param {ModelKey | ModelKey[]} id_or_ids
     */
    public static async destroy(id_or_ids: ModelKey | ModelKey[]) {
        const ids = Array.isArray(id_or_ids) ? id_or_ids : [id_or_ids]
        const constructor = (this.constructor as typeof Model)
        const mutable = this.delete()
            .whereIn(constructor.qualified_key_name(), ids)
            .target_operator(make(ObjectResultOperator))
            .results()

        const result = await mutable

        const modified_rows = await mutable.count()
        if ( modified_rows !== ids.length ) {
            logger.warn(`Model bulk destroy modified ${modified_rows} when ${ids.length} keys were provided. (Key: ${constructor.qualified_key_name()})`)
        }
    }

    /**
     * Delete this model's record from the database.
     */
    public async destroy(): Promise<void> {
        await this.deleting$.next(this)

        const constructor = (this.constructor as typeof Model)
        const mutable = this.delete()
            .where(constructor.qualified_key_name, '=', this.key())
            .target_operator(make(ObjectResultOperator))
            .results()

        const result = await mutable

        const modified_rows = await mutable.count()
        if ( modified_rows !== 1 ) {
            logger.warn(`Model delete modified ${modified_rows} rows! (Key: ${constructor.qualified_key_name()})`)
        }

        await this.deleted$.next(this)
    }

    /**
     * Convert this model's record to a plain object.
     * @return object
     */
    public to_object(): { [key: string]: any } {
        const constructor = (this.constructor as typeof Model)
        const obj = {}
        this.field_defs()
            .each(field_def => {
                // @ts-ignore
                obj[field_def.model_key] = this[field_def.model_key]
            })

        constructor.appends.forEach(appended_field => {
            // @ts-ignore
            obj[appended_field] = this[appended_field]
        })

        constructor.masks.forEach(masked_field => {
            // @ts-ignore
            delete obj[masked_field]
        })

        return obj
    }

    /**
     * Convert this model's record to a JSON string.
     * @return string
     */
    public to_json(): string {
        return JSON.stringify(this.to_object())
    }

    /**
     * Fetch a fresh instance of this model's record from the database.
     * @return Model
     */
    public async fresh(): Promise<Model<T>> {
        const constructor = (this.constructor as typeof Model)
        const fields = this.field_defs()
            .whereNot('model_key', '=', this.key_name())
            .pluck('database_key')
            .toArray()

        const result = await constructor.select(...fields)
            .where(constructor.qualified_key_name(), '=', this.key())
            .limit(1)
            .results()
        return result.first()
    }

    /**
     * Re-fetch the fields on this model from the database.
     */
    public async refresh() {
        const constructor = (this.constructor as typeof Model)
        const values = await this.select(this._loaded_database_fields())
            .where(constructor.qualified_key_name(), '=', this.key())
            .limit(1)
            .target_operator(make(ObjectResultOperator))
            .results()

        const row = values.first()
        if ( row ) this.assume_from_source(row)
    }

    /**
     * Populate the fields on the given model from the fields on this model, except for the key.
     * @param Model other
     * @return Model
     */
    public populate(other: Model<T>): Model<T> {
        const row = this.to_row()
        delete row[this.key_name()]
        other.assume_from_source(row)
        return other
    }

    /**
     * Given another model, determines if that model represents the same
     * record as this model.
     * @param Model other_instance
     * @return boolean
     */
    public is(other_instance: Model<any>): boolean {
        const this_constructor = (this.constructor as typeof Model)
        const other_constructor = (other_instance.constructor as typeof Model)
        return (
            other_instance.key() === this.key()
            && this_constructor.qualified_key_name() === other_constructor.qualified_key_name()
        )
    }

    /**
     * Given another model, determines if that model represents a different
     * record as this model.
     * @param Model other_instance
     * @return boolean
     */
    public is_not(other_instance: Model<any>): boolean {
        return !this.is(other_instance)
    }

    /**
     * Returns the field name of the primary key for this model.
     * @return string
     */
    public key_name() {
        return (this.constructor as typeof Model).key
    }

    /**
     * If defined, returns the value of the primary key for this model.
     */
    public key(): ModelKey {
        return this?._original?.[(this.constructor as typeof Model).key]
    }

    /**
     * Returns the table-qualified field name of the primary key for this model.
     */
    public static qualified_key_name() {
        return `${this.table_name()}.${this.key}`
    }

    /**
     * Dehydrate the model. Implements Rehydratable interface.
     */
    public async dehydrate(): Promise<JSONState> {
        return this.to_object()
    }

    /**
     * Rehydrate the model. Implements Rehydratable interface.
     * @param state
     */
    public async rehydrate(state: JSONState) {
        this.assume_from_source(state)
    }
}