import {ValidationError} from '../error/validation_error';
import {getType} from '../util/get_type';
import {validateObject} from './validate_object';
import {validateArray} from './validate_array';
import {validateNumber} from './validate_number';
import {isExpression} from '../expression';
import {unbundle, deepUnbundle} from '../util/unbundle_jsonlint';
import {
    supportsPropertyExpression,
    supportsZoomExpression,
    supportsInterpolation
} from '../util/properties';

export function validateFunction(options): Array<ValidationError> {
    const functionValueSpec = options.valueSpec;
    const functionType = unbundle(options.value.type);
    let stopKeyType;
    let stopDomainValues = {};
    let previousStopDomainValue;
    let previousStopDomainZoom;

    const isZoomFunction = functionType !== 'categorical' && options.value.property === undefined;
    const isPropertyFunction = !isZoomFunction;
    const isZoomAndPropertyFunction =
        getType(options.value.stops) === 'array' &&
        getType(options.value.stops[0]) === 'array' &&
        getType(options.value.stops[0][0]) === 'object';

    const errors = validateObject({
        key: options.key,
        value: options.value,
        valueSpec: options.styleSpec.function,
        validateSpec: options.validateSpec,
        style: options.style,
        styleSpec: options.styleSpec,
        objectElementValidators: {
            stops: validateFunctionStops,
            default: validateFunctionDefault
        }
    });

    if (functionType === 'identity' && isZoomFunction) {
        errors.push(
            new ValidationError(options.key, options.value, 'missing required property "property"')
        );
    }

    if (functionType !== 'identity' && !options.value.stops) {
        errors.push(
            new ValidationError(options.key, options.value, 'missing required property "stops"')
        );
    }

    if (
        functionType === 'exponential' &&
        options.valueSpec.expression &&
        !supportsInterpolation(options.valueSpec)
    ) {
        errors.push(
            new ValidationError(options.key, options.value, 'exponential functions not supported')
        );
    }

    if (options.styleSpec.$version >= 8) {
        if (isPropertyFunction && !supportsPropertyExpression(options.valueSpec)) {
            errors.push(
                new ValidationError(options.key, options.value, 'property functions not supported')
            );
        } else if (isZoomFunction && !supportsZoomExpression(options.valueSpec)) {
            errors.push(
                new ValidationError(options.key, options.value, 'zoom functions not supported')
            );
        }
    }

    if (
        (functionType === 'categorical' || isZoomAndPropertyFunction) &&
        options.value.property === undefined
    ) {
        errors.push(
            new ValidationError(options.key, options.value, '"property" property is required')
        );
    }

    return errors;

    function validateFunctionStops(options) {
        if (functionType === 'identity') {
            return [
                new ValidationError(
                    options.key,
                    options.value,
                    'identity function may not have a "stops" property'
                )
            ];
        }

        let errors = [];
        const value = options.value;

        errors = errors.concat(
            validateArray({
                key: options.key,
                value,
                valueSpec: options.valueSpec,
                validateSpec: options.validateSpec,
                style: options.style,
                styleSpec: options.styleSpec,
                arrayElementValidator: validateFunctionStop
            })
        );

        if (getType(value) === 'array' && value.length === 0) {
            errors.push(
                new ValidationError(options.key, value, 'array must have at least one stop')
            );
        }

        return errors;
    }

    function validateFunctionStop(options) {
        let errors = [];
        const value = options.value;
        const key = options.key;

        if (getType(value) !== 'array') {
            return [new ValidationError(key, value, `array expected, ${getType(value)} found`)];
        }

        if (value.length !== 2) {
            return [
                new ValidationError(
                    key,
                    value,
                    `array length 2 expected, length ${value.length} found`
                )
            ];
        }

        if (isZoomAndPropertyFunction) {
            if (getType(value[0]) !== 'object') {
                return [
                    new ValidationError(key, value, `object expected, ${getType(value[0])} found`)
                ];
            }
            if (value[0].zoom === undefined) {
                return [new ValidationError(key, value, 'object stop key must have zoom')];
            }
            if (value[0].value === undefined) {
                return [new ValidationError(key, value, 'object stop key must have value')];
            }
            if (previousStopDomainZoom && previousStopDomainZoom > unbundle(value[0].zoom)) {
                return [
                    new ValidationError(
                        key,
                        value[0].zoom,
                        'stop zoom values must appear in ascending order'
                    )
                ];
            }
            if (unbundle(value[0].zoom) !== previousStopDomainZoom) {
                previousStopDomainZoom = unbundle(value[0].zoom);
                previousStopDomainValue = undefined;
                stopDomainValues = {};
            }
            errors = errors.concat(
                validateObject({
                    key: `${key}[0]`,
                    value: value[0],
                    valueSpec: {zoom: {}},
                    validateSpec: options.validateSpec,
                    style: options.style,
                    styleSpec: options.styleSpec,
                    objectElementValidators: {
                        zoom: validateNumber,
                        value: validateStopDomainValue
                    }
                })
            );
        } else {
            errors = errors.concat(
                validateStopDomainValue(
                    {
                        key: `${key}[0]`,
                        value: value[0],
                        valueSpec: {},
                        validateSpec: options.validateSpec,
                        style: options.style,
                        styleSpec: options.styleSpec
                    },
                    value
                )
            );
        }

        if (isExpression(deepUnbundle(value[1]))) {
            return errors.concat([
                new ValidationError(
                    `${key}[1]`,
                    value[1],
                    'expressions are not allowed in function stops.'
                )
            ]);
        }

        return errors.concat(
            options.validateSpec({
                key: `${key}[1]`,
                value: value[1],
                valueSpec: functionValueSpec,
                validateSpec: options.validateSpec,
                style: options.style,
                styleSpec: options.styleSpec
            })
        );
    }

    function validateStopDomainValue(options, stop) {
        const type = getType(options.value);
        const value = unbundle(options.value);

        const reportValue = options.value !== null ? options.value : stop;

        if (!stopKeyType) {
            stopKeyType = type;
        } else if (type !== stopKeyType) {
            return [
                new ValidationError(
                    options.key,
                    reportValue,
                    `${type} stop domain type must match previous stop domain type ${stopKeyType}`
                )
            ];
        }

        if (type !== 'number' && type !== 'string' && type !== 'boolean') {
            return [
                new ValidationError(
                    options.key,
                    reportValue,
                    'stop domain value must be a number, string, or boolean'
                )
            ];
        }

        if (type !== 'number' && functionType !== 'categorical') {
            let message = `number expected, ${type} found`;
            if (supportsPropertyExpression(functionValueSpec) && functionType === undefined) {
                message +=
                    '\nIf you intended to use a categorical function, specify `"type": "categorical"`.';
            }
            return [new ValidationError(options.key, reportValue, message)];
        }

        if (
            functionType === 'categorical' &&
            type === 'number' &&
            (!isFinite(value as number) || Math.floor(value as number) !== value)
        ) {
            return [
                new ValidationError(options.key, reportValue, `integer expected, found ${value}`)
            ];
        }

        if (
            functionType !== 'categorical' &&
            type === 'number' &&
            previousStopDomainValue !== undefined &&
            value < previousStopDomainValue
        ) {
            return [
                new ValidationError(
                    options.key,
                    reportValue,
                    'stop domain values must appear in ascending order'
                )
            ];
        } else {
            previousStopDomainValue = value;
        }

        if (functionType === 'categorical' && (value as any) in stopDomainValues) {
            return [
                new ValidationError(options.key, reportValue, 'stop domain values must be unique')
            ];
        } else {
            stopDomainValues[value as any] = true;
        }

        return [];
    }

    function validateFunctionDefault(options): Array<ValidationError> {
        return options.validateSpec({
            key: options.key,
            value: options.value,
            valueSpec: functionValueSpec,
            validateSpec: options.validateSpec,
            style: options.style,
            styleSpec: options.styleSpec
        });
    }
}