import {toString,
    NumberType,
    StringType,
    BooleanType,
    ColorType,
    ObjectType,
    ValueType,
    ErrorType,
    CollatorType,
    array,
    toString as typeToString,
} from './types';

import ParsingContext from './parsing_context';
import EvaluationContext from './evaluation_context';

import {expressions} from './definitions/index';
import CollatorExpression from './definitions/collator';
import Within from './definitions/within';
import Literal from './definitions/literal';
import Assertion from './definitions/assertion';
import Coercion from './definitions/coercion';
import Var from './definitions/var';
import Distance from './definitions/distance';

import type {Expression, ExpressionRegistry} from './expression';
import type {Value} from './values';
import type {Type} from './types';

import {typeOf, Color, validateRGBA, toString as valueToString} from './values';
import RuntimeError from './runtime_error';

export type Varargs = {
    type: Type;
};
type Signature = Array<Type> | Varargs;
type Evaluate = (b: EvaluationContext, a: Array<Expression>) => Value;

type Definition = [Type, Signature, Evaluate] | {
    type: Type;
    overloads: Array<[Signature, Evaluate]>;
};

class CompoundExpression implements Expression {
    name: string;
    type: Type;
    _evaluate: Evaluate;
    args: Array<Expression>;

    static definitions: {[_: string]: Definition};

    constructor(name: string, type: Type, evaluate: Evaluate, args: Array<Expression>) {
        this.name = name;
        this.type = type;
        this._evaluate = evaluate;
        this.args = args;
    }

    evaluate(ctx: EvaluationContext) {
        return this._evaluate(ctx, this.args);
    }

    eachChild(fn: (_: Expression) => void) {
        this.args.forEach(fn);
    }

    outputDefined() {
        return false;
    }

    static parse(args: ReadonlyArray<unknown>, context: ParsingContext): Expression {
        const op: string = (args[0] as any);
        const definition = CompoundExpression.definitions[op];
        if (!definition) {
            return context.error(`Unknown expression "${op}". If you wanted a literal array, use ["literal", [...]].`, 0) as null;
        }

        // Now check argument types against each signature
        const type = Array.isArray(definition) ?
            definition[0] : definition.type;

        const availableOverloads = Array.isArray(definition) ?
            [[definition[1], definition[2]]] :
            definition.overloads;

        const overloads = availableOverloads.filter(([signature]) => (
            !Array.isArray(signature) || // varags
            signature.length === args.length - 1 // correct param count
        ));

        let signatureContext: ParsingContext = null;

        for (const [params, evaluate] of overloads) {
            // Use a fresh context for each attempted signature so that, if
            // we eventually succeed, we haven't polluted `context.errors`.
            signatureContext = new ParsingContext(context.registry, isExpressionConstant, context.path, null, context.scope);

            // First parse all the args, potentially coercing to the
            // types expected by this overload.
            const parsedArgs: Array<Expression> = [];
            let argParseFailed = false;
            for (let i = 1; i < args.length; i++) {
                const arg = args[i];
                const expectedType = Array.isArray(params) ?
                    params[i - 1] :
                    (params as Varargs).type;

                const parsed = signatureContext.parse(arg, 1 + parsedArgs.length, expectedType);
                if (!parsed) {
                    argParseFailed = true;
                    break;
                }
                parsedArgs.push(parsed);
            }
            if (argParseFailed) {
                // Couldn't coerce args of this overload to expected type, move
                // on to next one.
                continue;
            }

            if (Array.isArray(params)) {
                if (params.length !== parsedArgs.length) {
                    signatureContext.error(`Expected ${params.length} arguments, but found ${parsedArgs.length} instead.`);
                    continue;
                }
            }

            for (let i = 0; i < parsedArgs.length; i++) {
                const expected = Array.isArray(params) ? params[i] : (params as Varargs).type;
                const arg = parsedArgs[i];
                signatureContext.concat(i + 1).checkSubtype(expected, arg.type);
            }

            if (signatureContext.errors.length === 0) {
                return new CompoundExpression(op, type, evaluate as Evaluate, parsedArgs);
            }
        }

        if (overloads.length === 1) {
            context.errors.push(...signatureContext.errors);
        } else {
            const expected = overloads.length ? overloads : availableOverloads;
            const signatures = expected
                .map(([params]) => stringifySignature(params as Signature))
                .join(' | ');

            const actualTypes = [];
            // For error message, re-parse arguments without trying to
            // apply any coercions
            for (let i = 1; i < args.length; i++) {
                const parsed = context.parse(args[i], 1 + actualTypes.length);
                if (!parsed) return null;
                actualTypes.push(toString(parsed.type));
            }
            context.error(`Expected arguments of type ${signatures}, but found (${actualTypes.join(', ')}) instead.`);
        }

        return null;
    }

    static register(
        registry: ExpressionRegistry,
        definitions: {[_: string]: Definition}
    ) {
        CompoundExpression.definitions = definitions;
        for (const name in definitions) {
            registry[name] = CompoundExpression;
        }
    }
}

function rgba(ctx, [r, g, b, a]) {
    r = r.evaluate(ctx);
    g = g.evaluate(ctx);
    b = b.evaluate(ctx);
    const alpha = a ? a.evaluate(ctx) : 1;
    const error = validateRGBA(r, g, b, alpha);
    if (error) throw new RuntimeError(error);
    return new Color(r / 255, g / 255, b / 255, alpha, false);
}

function has(key, obj) {
    return key in obj;
}

function get(key, obj) {
    const v = obj[key];
    return typeof v === 'undefined' ? null : v;
}

function binarySearch(v, a, i, j) {
    while (i <= j) {
        const m = (i + j) >> 1;
        if (a[m] === v)
            return true;
        if (a[m] > v)
            j = m - 1;
        else
            i = m + 1;
    }
    return false;
}

function varargs(type: Type): Varargs {
    return {type};
}

CompoundExpression.register(expressions, {
    'error': [
        ErrorType,
        [StringType],
        (ctx, [v]) => { throw new RuntimeError(v.evaluate(ctx)); }
    ],
    'typeof': [
        StringType,
        [ValueType],
        (ctx, [v]) => typeToString(typeOf(v.evaluate(ctx)))
    ],
    'to-rgba': [
        array(NumberType, 4),
        [ColorType],
        (ctx, [v]) => {
            const [r, g, b, a] = v.evaluate(ctx).rgb;
            return [r * 255, g * 255, b * 255, a];
        },
    ],
    'rgb': [
        ColorType,
        [NumberType, NumberType, NumberType],
        rgba
    ],
    'rgba': [
        ColorType,
        [NumberType, NumberType, NumberType, NumberType],
        rgba
    ],
    'has': {
        type: BooleanType,
        overloads: [
            [
                [StringType],
                (ctx, [key]) => has(key.evaluate(ctx), ctx.properties())
            ], [
                [StringType, ObjectType],
                (ctx, [key, obj]) => has(key.evaluate(ctx), obj.evaluate(ctx))
            ]
        ]
    },
    'get': {
        type: ValueType,
        overloads: [
            [
                [StringType],
                (ctx, [key]) => get(key.evaluate(ctx), ctx.properties())
            ], [
                [StringType, ObjectType],
                (ctx, [key, obj]) => get(key.evaluate(ctx), obj.evaluate(ctx))
            ]
        ]
    },
    'feature-state': [
        ValueType,
        [StringType],
        (ctx, [key]) => get(key.evaluate(ctx), ctx.featureState || {})
    ],
    'properties': [
        ObjectType,
        [],
        (ctx) => ctx.properties()
    ],
    'geometry-type': [
        StringType,
        [],
        (ctx) => ctx.geometryType()
    ],
    'id': [
        ValueType,
        [],
        (ctx) => ctx.id()
    ],
    'zoom': [
        NumberType,
        [],
        (ctx) => ctx.globals.zoom
    ],
    'heatmap-density': [
        NumberType,
        [],
        (ctx) => ctx.globals.heatmapDensity || 0
    ],
    'line-progress': [
        NumberType,
        [],
        (ctx) => ctx.globals.lineProgress || 0
    ],
    'accumulated': [
        ValueType,
        [],
        (ctx) => ctx.globals.accumulated === undefined ? null : ctx.globals.accumulated
    ],
    '+': [
        NumberType,
        varargs(NumberType),
        (ctx, args) => {
            let result = 0;
            for (const arg of args) {
                result += arg.evaluate(ctx);
            }
            return result;
        }
    ],
    '*': [
        NumberType,
        varargs(NumberType),
        (ctx, args) => {
            let result = 1;
            for (const arg of args) {
                result *= arg.evaluate(ctx);
            }
            return result;
        }
    ],
    '-': {
        type: NumberType,
        overloads: [
            [
                [NumberType, NumberType],
                (ctx, [a, b]) => a.evaluate(ctx) - b.evaluate(ctx)
            ], [
                [NumberType],
                (ctx, [a]) => -a.evaluate(ctx)
            ]
        ]
    },
    '/': [
        NumberType,
        [NumberType, NumberType],
        (ctx, [a, b]) => a.evaluate(ctx) / b.evaluate(ctx)
    ],
    '%': [
        NumberType,
        [NumberType, NumberType],
        (ctx, [a, b]) => a.evaluate(ctx) % b.evaluate(ctx)
    ],
    'ln2': [
        NumberType,
        [],
        () => Math.LN2
    ],
    'pi': [
        NumberType,
        [],
        () => Math.PI
    ],
    'e': [
        NumberType,
        [],
        () => Math.E
    ],
    '^': [
        NumberType,
        [NumberType, NumberType],
        (ctx, [b, e]) => Math.pow(b.evaluate(ctx), e.evaluate(ctx))
    ],
    'sqrt': [
        NumberType,
        [NumberType],
        (ctx, [x]) => Math.sqrt(x.evaluate(ctx))
    ],
    'log10': [
        NumberType,
        [NumberType],
        (ctx, [n]) => Math.log(n.evaluate(ctx)) / Math.LN10
    ],
    'ln': [
        NumberType,
        [NumberType],
        (ctx, [n]) => Math.log(n.evaluate(ctx))
    ],
    'log2': [
        NumberType,
        [NumberType],
        (ctx, [n]) => Math.log(n.evaluate(ctx)) / Math.LN2
    ],
    'sin': [
        NumberType,
        [NumberType],
        (ctx, [n]) => Math.sin(n.evaluate(ctx))
    ],
    'cos': [
        NumberType,
        [NumberType],
        (ctx, [n]) => Math.cos(n.evaluate(ctx))
    ],
    'tan': [
        NumberType,
        [NumberType],
        (ctx, [n]) => Math.tan(n.evaluate(ctx))
    ],
    'asin': [
        NumberType,
        [NumberType],
        (ctx, [n]) => Math.asin(n.evaluate(ctx))
    ],
    'acos': [
        NumberType,
        [NumberType],
        (ctx, [n]) => Math.acos(n.evaluate(ctx))
    ],
    'atan': [
        NumberType,
        [NumberType],
        (ctx, [n]) => Math.atan(n.evaluate(ctx))
    ],
    'min': [
        NumberType,
        varargs(NumberType),
        (ctx, args) => Math.min(...args.map(arg => arg.evaluate(ctx)))
    ],
    'max': [
        NumberType,
        varargs(NumberType),
        (ctx, args) => Math.max(...args.map(arg => arg.evaluate(ctx)))
    ],
    'abs': [
        NumberType,
        [NumberType],
        (ctx, [n]) => Math.abs(n.evaluate(ctx))
    ],
    'round': [
        NumberType,
        [NumberType],
        (ctx, [n]) => {
            const v = n.evaluate(ctx);
            // Javascript's Math.round() rounds towards +Infinity for halfway
            // values, even when they're negative. It's more common to round
            // away from 0 (e.g., this is what python and C++ do)
            return v < 0 ? -Math.round(-v) : Math.round(v);
        }
    ],
    'floor': [
        NumberType,
        [NumberType],
        (ctx, [n]) => Math.floor(n.evaluate(ctx))
    ],
    'ceil': [
        NumberType,
        [NumberType],
        (ctx, [n]) => Math.ceil(n.evaluate(ctx))
    ],
    'filter-==': [
        BooleanType,
        [StringType, ValueType],
        (ctx, [k, v]) => ctx.properties()[(k as any).value] === (v as any).value
    ],
    'filter-id-==': [
        BooleanType,
        [ValueType],
        (ctx, [v]) => ctx.id() === (v as any).value
    ],
    'filter-type-==': [
        BooleanType,
        [StringType],
        (ctx, [v]) => ctx.geometryType() === (v as any).value
    ],
    'filter-<': [
        BooleanType,
        [StringType, ValueType],
        (ctx, [k, v]) => {
            const a = ctx.properties()[(k as any).value];
            const b = (v as any).value;
            return typeof a === typeof b && a < b;
        }
    ],
    'filter-id-<': [
        BooleanType,
        [ValueType],
        (ctx, [v]) => {
            const a = ctx.id();
            const b = (v as any).value;
            return typeof a === typeof b && a < b;
        }
    ],
    'filter->': [
        BooleanType,
        [StringType, ValueType],
        (ctx, [k, v]) => {
            const a = ctx.properties()[(k as any).value];
            const b = (v as any).value;
            return typeof a === typeof b && a > b;
        }
    ],
    'filter-id->': [
        BooleanType,
        [ValueType],
        (ctx, [v]) => {
            const a = ctx.id();
            const b = (v as any).value;
            return typeof a === typeof b && a > b;
        }
    ],
    'filter-<=': [
        BooleanType,
        [StringType, ValueType],
        (ctx, [k, v]) => {
            const a = ctx.properties()[(k as any).value];
            const b = (v as any).value;
            return typeof a === typeof b && a <= b;
        }
    ],
    'filter-id-<=': [
        BooleanType,
        [ValueType],
        (ctx, [v]) => {
            const a = ctx.id();
            const b = (v as any).value;
            return typeof a === typeof b && a <= b;
        }
    ],
    'filter->=': [
        BooleanType,
        [StringType, ValueType],
        (ctx, [k, v]) => {
            const a = ctx.properties()[(k as any).value];
            const b = (v as any).value;
            return typeof a === typeof b && a >= b;
        }
    ],
    'filter-id->=': [
        BooleanType,
        [ValueType],
        (ctx, [v]) => {
            const a = ctx.id();
            const b = (v as any).value;
            return typeof a === typeof b && a >= b;
        }
    ],
    'filter-has': [
        BooleanType,
        [ValueType],
        (ctx, [k]) => (k as any).value in ctx.properties()
    ],
    'filter-has-id': [
        BooleanType,
        [],
        (ctx) => (ctx.id() !== null && ctx.id() !== undefined)
    ],
    'filter-type-in': [
        BooleanType,
        [array(StringType)],
        (ctx, [v]) => (v as any).value.indexOf(ctx.geometryType()) >= 0
    ],
    'filter-id-in': [
        BooleanType,
        [array(ValueType)],
        (ctx, [v]) => (v as any).value.indexOf(ctx.id()) >= 0
    ],
    'filter-in-small': [
        BooleanType,
        [StringType, array(ValueType)],
        // assumes v is an array literal
        (ctx, [k, v]) => (v as any).value.indexOf(ctx.properties()[(k as any).value]) >= 0
    ],
    'filter-in-large': [
        BooleanType,
        [StringType, array(ValueType)],
        // assumes v is a array literal with values sorted in ascending order and of a single type
        (ctx, [k, v]) => binarySearch(ctx.properties()[(k as any).value], (v as any).value, 0, (v as any).value.length - 1)
    ],
    'all': {
        type: BooleanType,
        overloads: [
            [
                [BooleanType, BooleanType],
                (ctx, [a, b]) => a.evaluate(ctx) && b.evaluate(ctx)
            ],
            [
                varargs(BooleanType),
                (ctx, args) => {
                    for (const arg of args) {
                        if (!arg.evaluate(ctx))
                            return false;
                    }
                    return true;
                }
            ]
        ]
    },
    'any': {
        type: BooleanType,
        overloads: [
            [
                [BooleanType, BooleanType],
                (ctx, [a, b]) => a.evaluate(ctx) || b.evaluate(ctx)
            ],
            [
                varargs(BooleanType),
                (ctx, args) => {
                    for (const arg of args) {
                        if (arg.evaluate(ctx))
                            return true;
                    }
                    return false;
                }
            ]
        ]
    },
    '!': [
        BooleanType,
        [BooleanType],
        (ctx, [b]) => !b.evaluate(ctx)
    ],
    'is-supported-script': [
        BooleanType,
        [StringType],
        // At parse time this will always return true, so we need to exclude this expression with isGlobalPropertyConstant
        (ctx, [s]) => {
            const isSupportedScript = ctx.globals && ctx.globals.isSupportedScript;
            if (isSupportedScript) {
                return isSupportedScript(s.evaluate(ctx));
            }
            return true;
        }
    ],
    'upcase': [
        StringType,
        [StringType],
        (ctx, [s]) => s.evaluate(ctx).toUpperCase()
    ],
    'downcase': [
        StringType,
        [StringType],
        (ctx, [s]) => s.evaluate(ctx).toLowerCase()
    ],
    'concat': [
        StringType,
        varargs(ValueType),
        (ctx, args) => args.map(arg => valueToString(arg.evaluate(ctx))).join('')
    ],
    'resolved-locale': [
        StringType,
        [CollatorType],
        (ctx, [collator]) => collator.evaluate(ctx).resolvedLocale()
    ]
});

function stringifySignature(signature: Signature): string {
    if (Array.isArray(signature)) {
        return `(${signature.map(toString).join(', ')})`;
    } else {
        return `(${toString(signature.type)}...)`;
    }
}

function isExpressionConstant(expression: Expression) {
    if (expression instanceof Var) {
        return isExpressionConstant(expression.boundExpression);
    } else if (expression instanceof CompoundExpression && expression.name === 'error') {
        return false;
    } else if (expression instanceof CollatorExpression) {
        // Although the results of a Collator expression with fixed arguments
        // generally shouldn't change between executions, we can't serialize them
        // as constant expressions because results change based on environment.
        return false;
    } else if (expression instanceof Within) {
        return false;
    } else if (expression instanceof Distance) {
        return false;
    }

    const isTypeAnnotation = expression instanceof Coercion ||
        expression instanceof Assertion;

    let childrenConstant = true;
    expression.eachChild(child => {
        // We can _almost_ assume that if `expressions` children are constant,
        // they would already have been evaluated to Literal values when they
        // were parsed.  Type annotations are the exception, because they might
        // have been inferred and added after a child was parsed.

        // So we recurse into isConstant() for the children of type annotations,
        // but otherwise simply check whether they are Literals.
        if (isTypeAnnotation) {
            childrenConstant = childrenConstant && isExpressionConstant(child);
        } else {
            childrenConstant = childrenConstant && child instanceof Literal;
        }
    });
    if (!childrenConstant) {
        return false;
    }

    return isFeatureConstant(expression) &&
           isGlobalPropertyConstant(expression,
               ['zoom', 'heatmap-density', 'line-progress', 'accumulated', 'is-supported-script']);
}

function isFeatureConstant(e: Expression) {
    if (e instanceof CompoundExpression) {
        if (e.name === 'get' && e.args.length === 1) {
            return false;
        } else if (e.name === 'feature-state') {
            return false;
        } else if (e.name === 'has' && e.args.length === 1) {
            return false;
        } else if (
            e.name === 'properties' ||
            e.name === 'geometry-type' ||
            e.name === 'id'
        ) {
            return false;
        } else if (/^filter-/.test(e.name)) {
            return false;
        }
    }

    if (e instanceof Within) {
        return false;
    }
    if (e instanceof Distance) {
        return false;
    }

    let result = true;
    e.eachChild(arg => {
        if (result && !isFeatureConstant(arg)) { result = false; }
    });
    return result;
}

function isStateConstant(e: Expression) {
    if (e instanceof CompoundExpression) {
        if (e.name === 'feature-state') {
            return false;
        }
    }
    let result = true;
    e.eachChild(arg => {
        if (result && !isStateConstant(arg)) { result = false; }
    });
    return result;
}

function isGlobalPropertyConstant(e: Expression, properties: Array<string>) {
    if (e instanceof CompoundExpression && properties.indexOf(e.name) >= 0) { return false; }
    let result = true;
    e.eachChild((arg) => {
        if (result && !isGlobalPropertyConstant(arg, properties)) { result = false; }
    });
    return result;
}

export {isFeatureConstant, isGlobalPropertyConstant, isStateConstant, isExpressionConstant};
export default CompoundExpression;