module dcd.server.autocomplete.ufcs;

import dcd.server.autocomplete.util;
import dsymbol.symbol;
import dsymbol.scope_;
import dcd.common.messages;
import std.functional : unaryFun;
import std.algorithm;
import std.array;
import std.range;
import dsymbol.builtin.names;
import std.string;
import dparse.lexer : tok;
import std.regex;
import containers.hashset : HashSet;

void lookupUFCS(Scope* completionScope, DSymbol* beforeDotSymbol, size_t cursorPosition, ref AutocompleteResponse response)
{
    // UFCS completion
    DSymbol*[] ufcsSymbols = getSymbolsForUFCS(completionScope, beforeDotSymbol, cursorPosition);
    response.completions ~= map!(s => createCompletionForUFCS(s))(ufcsSymbols).array;
}

AutocompleteResponse.Completion createCompletionForUFCS(const DSymbol* symbol)
{
    return AutocompleteResponse.Completion(symbol.name, CompletionKind.ufcsName, symbol.callTip, symbol
            .symbolFile, symbol
            .location, symbol
            .doc);
}

// Check if beforeDotSymbol is null or void
bool isInvalidForUFCSCompletion(const(DSymbol)* beforeDotSymbol)
{
    return beforeDotSymbol is null
        || beforeDotSymbol.name is getBuiltinTypeName(tok!"void")
        || (beforeDotSymbol.type !is null && beforeDotSymbol.type.name is getBuiltinTypeName(
                tok!"void"));
}
/**
 * Get symbols suitable for UFCS.
 *
 * a symbol is suitable for UFCS if it satisfies the following:
 * $(UL
 *  $(LI is global or imported)
 *  $(LI is callable with $(D beforeDotSymbol) as it's first argument)
 * )
 *
 * Params:
 *     completionScope = current scope
 *     beforeDotSymbol = the symbol before the dot (implicit first argument to UFCS function)
 *     cursorPosition = current position
 * Returns:
 *     callable an array of symbols suitable for UFCS at $(D cursorPosition)
 */
DSymbol*[] getSymbolsForUFCS(Scope* completionScope, const(DSymbol)* beforeDotSymbol, size_t cursorPosition)
{
    if (beforeDotSymbol.isInvalidForUFCSCompletion)
    {
        return null;
    }

    Scope* currentScope = completionScope.getScopeByCursor(cursorPosition);
    assert(currentScope);
    HashSet!size_t visited;

    // local appender
    FilteredAppender!(a => a.isCallableWithArg(beforeDotSymbol), DSymbol*[]) localAppender;

    while (currentScope !is null && currentScope.parent !is null)
    {
        auto localImports = currentScope.symbols.filter!(a => a.kind == CompletionKind.importSymbol);
        foreach (sym; localImports)
        {
            if (sym.type is null)
                continue;
            if (sym.qualifier == SymbolQualifier.selectiveImport)
                localAppender.put(sym.type);
            else
                sym.type.getParts(internString(null), localAppender, visited);
        }

        currentScope = currentScope.parent;
    }

    // global appender
    FilteredAppender!(a => a.isCallableWithArg(beforeDotSymbol, true), DSymbol*[]) globalAppender;

    // global symbols and global imports
    assert(currentScope !is null);
    assert(currentScope.parent is null);
    foreach (sym; currentScope.symbols)
    {
        if (sym.kind != CompletionKind.importSymbol)
            localAppender.put(sym);
        else if (sym.type !is null)
        {
            if (sym.qualifier == SymbolQualifier.selectiveImport)
                localAppender.put(sym.type);
            else
            {
                sym.type.getParts(istring(null), globalAppender, visited);
            }
        }
    }
    return localAppender.opSlice ~ globalAppender.opSlice;
}

/**
   Params:
   symbol = the symbol to check
   incomingSymbol = symbols we check on
   Returns:
   true if incomingSymbols first parameter matches beforeDotSymbol
   false otherwise
*/
bool isCallableWithArg(const(DSymbol)* incomingSymbol, const(DSymbol)* beforeDotSymbol, bool isGlobalScope = false)
{
    if (isGlobalScope && incomingSymbol.protection == tok!"private")
    {
        return false;
    }

    if (incomingSymbol.kind == CompletionKind.functionName && !incomingSymbol
        .functionParameters.empty)
    {
        return incomingSymbol.functionParameters.front.type is beforeDotSymbol;
    }

    return false;
}

/// $(D appender) with filter on $(D put)
struct FilteredAppender(alias predicate, T:
    T[] = DSymbol*[]) if (__traits(compiles, unaryFun!predicate(T.init) ? 0 : 0))
{
    alias pred = unaryFun!predicate;
    private Appender!(T[]) app;

    void put(T item)
    {
        if (pred(item))
            app.put(item);
    }

    void put(R)(R items) if (isInputRange!R && __traits(compiles, put(R.init.front)))
    {
        foreach (item; items)
            put(item);
    }

    void opOpAssign(string op : "~")(T rhs)
    {
        put(rhs);
    }

    alias app this;
}

@safe pure nothrow unittest
{
    FilteredAppender!("a%2", int[]) app;
    app.put(iota(10));
    assert(app.data == [1, 3, 5, 7, 9]);
}

bool doUFCSSearch(string beforeToken, string lastToken)
{
    // we do the search if they are different from eachother
    return beforeToken != lastToken;
}

void getUFCSParenCompletion(ref DSymbol*[] symbols, Scope* completionScope, istring firstToken, istring nextToken, size_t cursorPosition)
{
    DSymbol* firstSymbol = completionScope.getFirstSymbolByNameAndCursor(firstToken, cursorPosition);

    if (firstSymbol is null)
        return;

    DSymbol*[] possibleUFCSSymbol = completionScope.getSymbolsByNameAndCursor(nextToken, cursorPosition);
    foreach(nextSymbol; possibleUFCSSymbol){
        if (nextSymbol && nextSymbol.functionParameters)
        {
            if (firstSymbol.type is nextSymbol.functionParameters.front.type)
            {
                nextSymbol.kind = CompletionKind.ufcsName;
                symbols ~= nextSymbol;
            }
        }
    }
}