import { Pattern, NamedPattern, Schema, Input } from "./meta";
import * as M from './meta';
import { Annotated, Bytes, Dictionary, Fold, fold, preserves, Record, Tuple, Value } from "@preserves/core";
import { Formatter, parens, seq, Item, opseq, block, commas, brackets, anglebrackets, braces } from "./block";

function fnblock(... items: Item[]): Item {
    return seq('((() => ', block(... items), ')())');
}

export type CompileEnvEntry = {
    moduleName: string,
    modulePath: string,
    schema: Schema,
    inline: boolean,
};

export function compile(env: Array<CompileEnvEntry>, schema: Schema, preservesModule = '@preserves/core'): string {
    const literals = new Dictionary<string, never>();
    const types: Array<Item> = [];
    const predicates: Array<Item> = [];
    let temps: Array<string> = [];

    function environmentWith<R>(name: symbol,
                                kLocal: () => R,
                                kOther: (e: CompileEnvEntry, p: Pattern) => R): R {
        if (Schema._.definitions(schema).has(name)) {
            return kLocal();
        }
        for (const e of env) {
            const p = Schema._.definitions(e.schema).get(name);
            if (p !== void 0) {
                return kOther(e, p);
            }
        }
        throw new Error(`Undefined reference: ${name.description!}`);
    }

    function applyPredicate(name: symbol, v: string): Item {
        return environmentWith(name,
                               () => `is${name.description!}(${v})`,
                               (e, p) => {
                                   if (e.inline) {
                                       return walk(v, p);
                                   } else {
                                       return `${e.moduleName}.is${name.description!}(${v})`;
                                   }
                               });
    }

    function gentemp(): string {
        const varname = '_tmp' + temps.length;
        temps.push(varname);
        return varname;
    }

    function literal(v: Input): Item {
        let varname = literals.get(v);
        if (varname === void 0) {
            const s = '___' + (
                v.asPreservesText()
                    .replace('_', '__')
                    .replace('*', '_STAR_')
            );
            varname = M.isValidToken(s, true) ? s : '__lit' + literals.size;
            literals.set(v, varname);
        }
        return varname;
    }

    function typeFor(p: Pattern): Item {
        switch (p.label) {
            case M.___atom:
                switch (p[0]) {
                    case M.___Boolean: return `boolean`;
                    case M.___Float: return `_.SingleFloat`;
                    case M.___Double: return `_.DoubleFloat`;
                    case M.___SignedInteger: return `number`;
                    case M.___String: return `string`;
                    case M.___ByteString: return `_.Bytes`;
                    case M.___Symbol: return `symbol`;
                }
            case M.___lit:
                return `(typeof ${literal(p[0])})`;
            case M.___ref:
                return environmentWith(
                    p[0],
                    () => p[0].description!,
                    (e, pp) => {
                        if (e.inline) {
                            return typeFor(pp);
                        } else {
                            return `${e.moduleName}.${p[0].description!}`;
                        }
                    });
            case M.___or:
                return opseq('never', ' | ', ... p[0].map(pp => typeFor(pp)));
            case M.___and:
                return opseq('_.Value', ' & ', ... p[0].map(pp => typeFor(pp)));
            case M.___pointer:
                return `any`; // TODO: what to do here?
            case M.___rec:
                return seq('_.Record', anglebrackets(typeFor(p[0]), typeFor(p[1])));
            case M.___tuple:
                return brackets(... p[0].map(pp => typeFor(unname(pp))));
            case M.___tuple_STAR_:
                if (p[0].length === 0) {
                    return seq('Array<', typeFor(unname(p[1])), '>');
                } else {
                    return brackets(... p[0].map(pp => typeFor(unname(pp))),
                                    seq('... Array<', typeFor(unname(p[1])), '>'));
                }
            case M.___setof:
                return seq('_.KeyedSet<', typeFor(p[0]), '>');
            case M.___dictof:
                return seq('_.KeyedDictionary', anglebrackets(typeFor(p[0]), typeFor(p[1])));
            case M.___dict:
                return parens(seq(
                    block(
                        ... Array.from(p[0]).map(([k, vp]) =>
                            seq(`get(k: typeof ${literal(k)}): `, typeFor(vp))),
                        ... Array.from(p[0]).map(([k, _vp]) =>
                            seq(`has(k: typeof ${literal(k)}): true`))),
                    ' & _.Dictionary<_.Value>'));
            default:
                ((_p: never) => {})(p);
                throw new Error("Unreachable");
        }
    }

    function walk(v: string, p: Pattern, recordOkAsTuple = false): Item {
        switch (p.label) {
            case M.___atom:
                switch (p[0]) {
                    case M.___Boolean: return `typeof ${v} === 'boolean'`;
                    case M.___Float: return `_.Float.isSingle(${v})`;
                    case M.___Double: return `_.Float.isDouble(${v})`;
                    case M.___SignedInteger: return `typeof ${v} === 'number'`;
                    case M.___String: return `typeof ${v} === 'string'`;
                    case M.___ByteString: return `_.Bytes.isBytes(${v})`;
                    case M.___Symbol: return `typeof ${v} === 'symbol'`;
                }
            case M.___lit:
                switch (typeof p[0]) {
                    case 'boolean':
                    case 'number':
                    case 'string':
                    case 'symbol':
                        return `${v} === ${literal(p[0])}`;
                    default:
                        return `_.is(${v}, ${literal(p[0])})`;
                }
            case M.___ref:
                return applyPredicate(p[0], v);
            case M.___or:
                return opseq('false', ' || ', ... p[0].map(pp => walk(v, pp)));
            case M.___and:
                return opseq('true', ' && ', ... p[0].map(pp => walk(v, pp)));
            case M.___pointer:
                return `_.isPointer(${v})`;
            case M.___rec:
                return opseq('true', ' && ',
                             `_.Record.isRecord(${v})`,
                             walk(`${v}.label`, p[0]),
                             walk(v, p[1], true));
            case M.___tuple:
                return opseq('true', ' && ',
                             ... (recordOkAsTuple ? []
                                 : [`_.Array.isArray(${v})`, `!_.Record.isRecord(${v})`]),
                             `(${v}.length === ${p[0].length})`,
                             ... p[0].map((pp, i) => walk(`${v}[${i}]`, unname(pp))));
            case M.___tuple_STAR_:
                return opseq('true', ' && ',
                             ... (recordOkAsTuple ? []
                                 : [`_.Array.isArray(${v})`, `!_.Record.isRecord(${v})`]),
                             `(${v}.length >= ${p[0].length})`,
                             seq(`${v}.slice(${p[0].length})`,
                                 `.every(v => `,
                                 parens(walk('v', unname(p[1]))),
                                 `)`),
                             ... p[0].map((pp, i) => walk(`${v}[${i}]`, unname(pp))));
            case M.___setof:
                return opseq('true', ' && ',
                             `_.Set.isSet(${v})`,
                             fnblock(
                                 seq(`for (const vv of ${v}) `, block(
                                     seq('if (!(', walk('vv', p[0]), ')) return false'))),
                                 seq('return true')));
            case M.___dictof:
                return opseq('true', ' && ',
                             `_.Dictionary.isDictionary(${v})`,
                             fnblock(
                                 seq(`for (const e of ${v}) `, block(
                                     seq('if (!(', walk('e[0]', p[0]), ')) return false'),
                                     seq('if (!(', walk('e[1]', p[1]), ')) return false'))),
                                 seq('return true')));
            case M.___dict:
                return opseq('true', ' && ',
                             `_.Dictionary.isDictionary(${v})`,
                             ... Array.from(p[0]).map(([k, vp]) => {
                                 const tmp = gentemp();
                                 return parens(seq(
                                     `(${tmp} = ${v}.get(${literal(k)})) !== void 0 && `,
                                     walk(tmp, vp)));
                             }));
            default:
                ((_p: never) => {})(p);
                throw new Error("Unreachable");
        }
    }

    function unname(p: NamedPattern): Pattern {
        return (p.label === M.___named) ? p[1] : p;
    }

    function fieldName(np: NamedPattern, index: number): string {
        return (np.label === M.___named) ? np[0].description! : `_field${index}`;
    }

    function fieldEntry(np: NamedPattern, index: number): Item {
        return seq(JSON.stringify(fieldName(np, index)), ': ', typeFor(unname(np)));
    }

    for (const [name0, pattern] of Schema._.definitions(schema)) {
        const name = name0 as symbol;
        temps = [];
        const recognizer = walk('v', pattern);
        if (pattern.label === M.___rec &&
            pattern[0].label === M.___lit &&
            pattern[1].label === M.___tuple)
        {
            types.push(
                seq(`export const ${name.description!} = _.Record.makeConstructor<`,
                    braces(... pattern[1][0].map(fieldEntry)),
                    `>()(${literal(pattern[0][0])}, `,
                    JSON.stringify(pattern[1][0].map(fieldName)), `);`));
        }
        types.push(
            seq(`export type ${name.description!} = `, typeFor(pattern), `;`));
        predicates.push(
            seq('export function ', `is${name.description!}`,
                '(v: any): v is ', name.description!, ' ',
                block(
                    ... temps.length > 0 ? [seq('let ', commas(... temps), ': any')] : [],
                    seq('return ', recognizer))));
    }

    const f = new Formatter();
    f.write(`import * as _ from ${JSON.stringify(preservesModule)};\n`);
    f.newline();

    const sortedLiterals = Array.from(literals);
    sortedLiterals.sort((a, b) => a[1] < b[1] ? -1 : a[1] === b[1] ? 0 : 1);
    for (const [lit, varname] of sortedLiterals) {
        f.write(seq(`export const ${varname} = `, sourceCodeFor(lit), `;\n`));
    }
    f.newline();

    types.forEach(t => {
        f.write(t);
        f.newline();
        f.newline();
    });
    f.newline();

    predicates.forEach(p => {
        f.write(p);
        f.newline();
        f.newline();
    });

    return f.toString();
}

export function stringSource(s: string) {
    return JSON.stringify(s);
}

export function sourceCodeFor(v: Value<any>): Item {
    return fold(v, {
        boolean(b: boolean): Item { return b.toString(); },
        single(f: number): Item { return f.toString(); },
        double(f: number): Item { return f.toString(); },
        integer(i: number): Item { return i.toString(); },
        string(s: string): Item { return stringSource(s); },
        bytes(b: Bytes): Item {
            return seq(`Uint8Array.from(`, brackets(... Array.from(b).map(b => b.toString())), `)`);
        },
        symbol(s: symbol): Item { return `Symbol.for(${stringSource(s.description!)})`; },

        record(r: Record<Value<any>, Tuple<Value<any>>, any>, k: Fold<any, Item>): Item {
            return seq(`_.Record`, parens(k(r.label), brackets(... r.map(k))));
        },
        array(a: Array<Value<any>>, k: Fold<any, Item>): Item {
            return brackets(... a.map(k));
        },
        set(s: Set<any>, k: Fold<any, Item>): Item {
            return seq('new _.Set', parens(brackets(... Array.from(s).map(k))));
        },
        dictionary(d: Dictionary<Value<any>, any>, k: Fold<any, Item>): Item {
            return seq('new _.Dictionary', parens(brackets(... Array.from(d).map(([kk,vv]) =>
                brackets(k(kk), k(vv))))));
        },

        annotated(a: Annotated<any>, k: Fold<any, Item>): Item {
            return seq('_.annotate', parens(k(a.item), ... a.annotations.map(k)));
        },

        pointer(t: any, _k: Fold<any, Item>): Item {
            throw new Error(preserves`Cannot emit source code for construction of pointer ${t}`);
        },
    });
}