import { TextDocumentPositionParams, CompletionItem, CompletionItemKind, Range, MarkupContent } from "vscode-languageserver/node";
import { TextDocument } from "vscode-languageserver-textdocument";
import { PerlDocument, PerlElem, CompletionPrefix, PerlSymbolKind, completionElem, ElemSource} from "./types";
import { getPod } from "./pod";
import Uri from "vscode-uri";

export function getCompletions(
    params: TextDocumentPositionParams,
    perlDoc: PerlDocument,
    txtDoc: TextDocument,
    modMap: Map<string, string>
): CompletionItem[] {
    let position = params.position;
    const start = { line: position.line, character: 0 };
    const end = { line: position.line + 1, character: 0 };
    const text = txtDoc.getText({ start, end });
    const index = txtDoc.offsetAt(position) - txtDoc.offsetAt(start);

    const imPrefix = getImportPrefix(text, index);
    if (imPrefix) {
        const replace: Range = {
            start: { line: position.line, character: imPrefix.charStart },
            end: { line: position.line, character: imPrefix.charEnd },
        };

        const matches = getImportMatches(modMap, imPrefix.symbol, replace, perlDoc);
        return matches;
    } else {
        const prefix = getPrefix(text, index);

        if (!prefix.symbol) return [];

        const replace: Range = {
            start: { line: position.line, character: prefix.charStart },
            end: { line: position.line, character: prefix.charEnd },
        };

        const matches = getMatches(perlDoc, prefix.symbol, replace, prefix.stripPackage);
        return matches;
    }
}


export async function getCompletionDoc(elem: PerlElem, perlDoc: PerlDocument, modMap: Map<string, string>): Promise<string | undefined> {
    let docs = await getPod(elem, perlDoc, modMap);
    return docs;
}

// Similar to getSymbol for navigation, but don't "move right".
function getPrefix(text: string, position: number): CompletionPrefix {
    const canShift = (c: string) => /[\w\:\>\-]/.exec(c);
    let l = position - 1; // left
    for (; l >= 0 && canShift(text[l]); --l);
    
    if (l < 0 || text[l] != "$" && text[l] != "@" && text[l] != "%") ++l;

    let symbol = text.substring(l, position);
    const prefix = text.substring(0, l);
    let stripPackage = false;
    if (symbol.match(/^-(?:>\w*)?$/)) { // Matches -  or -> or ->\w
        // If you have Foo::Bar->new(...)->func, the extracted symbol will be ->func
        // We can special case this to Foo::Bar->func. The regex allows arguments to new(), including params with matched ()
        let match = prefix.match(/(\w(?:\w|::\w)*)->new\((?:\([^()]*\)|[^()])*\)$/);

        if (match){
            symbol = match[1] + symbol;
            stripPackage = true
        }
    }

    return { symbol: symbol, charStart: l, charEnd: position, stripPackage: stripPackage};
}

// First we check if it's an import statement, which is a special type of autocomplete with far more options
function getImportPrefix(text: string, position: number): CompletionPrefix | undefined {
    text = text.substring(0, position);

    let partialImport = /^\s*(?:use|require)\s+([\w:]+)$/.exec(text);
    if (!partialImport) return;
    const symbol = partialImport[1];

    return { symbol: symbol, charStart: position - symbol.length, charEnd: position, stripPackage: false };
}

function getImportMatches(modMap: Map<string, string>, symbol: string, replace: Range, perlDoc: PerlDocument): CompletionItem[] {
    const matches: CompletionItem[] = [];
    const mods = Array.from(modMap.keys());

    const lcSymbol = symbol.toLowerCase();
    modMap.forEach((modFile, mod) => {
        if (mod.toLowerCase().startsWith(lcSymbol)) {

            const modUri = Uri.parse(modFile).toString();
            const modElem: PerlElem = {
                name: symbol,
                type: PerlSymbolKind.Module,
                typeDetail: "",
                uri: modUri,
                package: symbol,
                line: 0,
                lineEnd: 0,
                value: "",
                source: ElemSource.modHunter,
            };
            const newElem: completionElem = {perlElem: modElem, docUri: perlDoc.uri}

            matches.push({
                label: mod,
                textEdit: { newText: mod, range: replace },
                kind: CompletionItemKind.Module,
                data: newElem
            });
        }
    });
    return matches;
}

function getMatches(perlDoc: PerlDocument, symbol: string, replace: Range, stripPackage: boolean): CompletionItem[] {
    let matches: CompletionItem[] = [];

    let qualifiedSymbol = symbol.replaceAll("->", "::"); // Module->method() can be found via Module::method
    if (qualifiedSymbol.endsWith('-'))
    	qualifiedSymbol = qualifiedSymbol.replace('-', ':');

    let bKnownObj = false;
    // Check if we know the type of this object
    let knownObject = /^(\$\w+):(?::\w*)?$/.exec(qualifiedSymbol);
    if (knownObject) {
        const targetVar = perlDoc.canonicalElems.get(knownObject[1]);
        if (targetVar) {
            qualifiedSymbol = qualifiedSymbol.replace(/^\$\w+(?=:)/, targetVar.typeDetail);
            bKnownObj = true;
        }
    }

    // If the magic variable $self->, then autocomplete to everything in main.
    const bSelf = /^(\$self):(?::\w*)?$/.exec(qualifiedSymbol);
    if (bSelf) bKnownObj = true;

    // const lcQualifiedSymbol = qualifiedSymbol.toLowerCase(); Case insensitive matches are hard since we restore what you originally matched on

    perlDoc.elems.forEach((elements: PerlElem[], elemName: string) => {
        if (/^[\$\@\%].$/.test(elemName)) return; // Remove single character magic perl variables. Mostly clutter the list

        let element = perlDoc.canonicalElems.get(elemName) || elements[0]; // Get the canonical (typed) element, otherwise just grab the first one.

        // All plain and inherited subroutines should match with $self. We're excluding PerlSymbolKind.ImportedSub here because imports clutter the list, despite perl allowing them called on $self->
        if (bSelf && [PerlSymbolKind.LocalSub, PerlSymbolKind.Inherited, PerlSymbolKind.LocalMethod, PerlSymbolKind.Field].includes(element.type))
            elemName = `$self::${elemName}`;

        if (goodMatch(perlDoc, elemName, qualifiedSymbol, symbol, bKnownObj)) {
            // Hooray, it's a match!
            // You may have asked for FOO::BAR->BAZ or $qux->BAZ and I found FOO::BAR::BAZ. Let's put back the arrow or variable before sending
            const quotedSymbol = qualifiedSymbol.replaceAll("$", "\\$"); // quotemeta for $self->FOO
            let aligned = elemName.replace(new RegExp(`^${quotedSymbol}`, "gi"), symbol);

            if (symbol.endsWith("-")) aligned = aligned.replaceAll('-:', "->"); // Half-arrows count too

            // Don't send invalid constructs
            // like FOO->BAR::BAZ
            if (/\-\>\w+::/.test(aligned)) return;
            // FOO->BAR if Bar is not a sub/method.
            if (
                /\-\>\w+$/.test(aligned) &&
                ![
                    PerlSymbolKind.LocalSub,
                    PerlSymbolKind.ImportedSub,
                    PerlSymbolKind.Inherited,
                    PerlSymbolKind.LocalMethod,
                    PerlSymbolKind.Method,
                    PerlSymbolKind.Field,
                    PerlSymbolKind.PathedField,
                ].includes(element.type)
            )
                return;
            // FOO::BAR if Bar is a instance method or attribute (I assume them to be instance methods/attributes, not class)
            if (
                !/^\$.*\-\>\w+$/.test(aligned) &&
                [PerlSymbolKind.LocalMethod, PerlSymbolKind.Method, PerlSymbolKind.Field, PerlSymbolKind.PathedField].includes(element.type)
            )
                return;
            if (
                aligned.indexOf("-:") != -1 || // We look things up like this, but don't let them slip through
		aligned.startsWith('$') && aligned.indexOf("::", 1) != -1
            )
                // $Foo::Bar, I don't really hunt for these anyway
                return;
            matches = matches.concat(buildMatches(aligned, element, replace, stripPackage, perlDoc));
        }
    });

    return matches;
}

// TODO: preprocess all "allowed" matches so we don't waste time iterating over them for every autocomplete.
function goodMatch(perlDoc: PerlDocument, elemName: string, qualifiedSymbol: string, origSymbol: string, bKnownObj: boolean): boolean {
    if (!elemName.startsWith(qualifiedSymbol)) return false;
    // All uppercase methods are generally private or autogenerated and unhelpful
    if (/(?:::|->)[A-Z][A-Z_]+$/.test(elemName)) return false;
    if (bKnownObj) {
        // If this is a known object type, we probably aren't importing the package or building a new one.
        if (/(?:::|->)(?:new|import)$/.test(elemName)) return false;
        // If we known the object type (and variable name is not $self), then exclude the double underscore private variables (rare anyway. single underscore kept, but ranked last in the autocomplete)
        if (origSymbol.startsWith('$') && !origSymbol.startsWith("$self") && /(?:::|->)__\w+$/.test(elemName)) return false;
        // Otherwise, always autocomplete, even if the module has not been explicitly imported.
        return true;
    }
    // Get the module name to see if it's been imported. Otherwise, don't allow it.
    let modRg = /^(.+)::.*?$/;
    var match = modRg.exec(elemName);
    if (match && !perlDoc.imported.has(match[1])) {
        // TODO: Allow completion on packages/class defined within the file itself (e.g. Foo->new, $foo->new already works)
        // Thing looks like a module, but was not explicitly imported
        return false;
    } else {
        // Thing was either explictly imported or not a module function
        return true;
    }
}

function buildMatches(lookupName: string, elem: PerlElem, range: Range, stripPackage: boolean, perlDoc: PerlDocument): CompletionItem[] {
    let kind: CompletionItemKind;
    let detail: string | undefined = undefined;
    let documentation: MarkupContent | undefined = undefined;
    let docs: string[] = [];

    if ([PerlSymbolKind.LocalVar, PerlSymbolKind.ImportedVar, PerlSymbolKind.Canonical].includes(elem.type)) {
        if (elem.typeDetail.length > 0) {
            kind = CompletionItemKind.Variable;
            detail = `${lookupName}: ${elem.typeDetail}`;
        } else if (lookupName == "$self") {
            kind = CompletionItemKind.Variable;
            // elem.package can be misleading if you use $self in two different packages in the same module. Get scoped matches will address this
            detail = `${lookupName}: ${elem.package}`;
        }
    }
    if (!detail) {
        switch (elem.type) {
            case PerlSymbolKind.LocalVar:
                kind = CompletionItemKind.Variable;
                break;
            case PerlSymbolKind.ImportedVar:
                kind = CompletionItemKind.Constant;
                // detail = elem.name;
                docs.push(elem.name);
                docs.push(`Value: ${elem.value}`);
                break;
            case PerlSymbolKind.ImportedHash:
            case PerlSymbolKind.Constant:
                kind = CompletionItemKind.Constant;
                break;
            case PerlSymbolKind.LocalSub:
                if (lookupName.startsWith("$self-")) docs.push(elem.name); // For consistency with the other $self methods. VScode seems to hide documentation if less populated?
                kind = CompletionItemKind.Function;
                break;
            case PerlSymbolKind.ImportedSub:
            case PerlSymbolKind.Inherited:
            case PerlSymbolKind.Method:
            case PerlSymbolKind.LocalMethod:
                kind = CompletionItemKind.Method;
                docs.push(elem.name);
                if (elem.typeDetail && elem.typeDetail != elem.name) docs.push(`\nDefined as:\n  ${elem.typeDetail}`);
                break;
            case PerlSymbolKind.Package:
            case PerlSymbolKind.Module:
                kind = CompletionItemKind.Module;
                break;
            case PerlSymbolKind.Label: // Loop labels
                kind = CompletionItemKind.Reference;
                break;
            case PerlSymbolKind.Class:
                kind = CompletionItemKind.Class;
                break;
            case PerlSymbolKind.Role:
                kind = CompletionItemKind.Interface;
                break;
            case PerlSymbolKind.Field:
            case PerlSymbolKind.PathedField:
                kind = CompletionItemKind.Field;
                break;
            case PerlSymbolKind.Phaser:
            case PerlSymbolKind.HttpRoute:
            case PerlSymbolKind.OutlineOnlySub:
                return [];
            default: // A sign that something needs fixing. Everything should've been enumerated.
                kind = CompletionItemKind.Property;
                break;
        }
    }
    if (docs.length > 0) documentation = { kind: "markdown", value: "```\n" + docs.join("\n") + "\n```" };

    let labelsToBuild = [lookupName];

    if (lookupName.endsWith("::new"))
        // Having ->new at the top (- sorts before :) is the more common way to call packages (although you can call it either way).
        labelsToBuild.push(lookupName.replace(/::new$/, "->new"));

    let matches: CompletionItem[] = [];

    labelsToBuild.forEach((label) => {

        let replaceText = label;
        if(stripPackage)
            // When autocompleting Foo->new(...)->, we need the dropdown to show Foo->func, but the replacement only to be ->func
            replaceText = replaceText.replace(/^(\w(?:\w|::\w)*)(?=->)/, '');

        const newElem: completionElem = {perlElem: elem, docUri: perlDoc.uri}

        matches.push({
            label: label,
            textEdit: { newText: replaceText, range },
            kind: kind,
            sortText: getSortText(label),
            detail: detail,
            documentation: documentation,
            data: newElem, 
        });
    });

    return matches;
}

function getSortText(label: string): string {
    // Ensure sorting has public methods up front, followed by private and then capital. (private vs somewhat capital is arbitrary, but public makes sense).
    // Variables will still be higher when relevant.
    // use English puts a lot of capital variables, so these will end up lower as well (including Hungarian notation capitals)

    let sortText: string;

    if (/^[@\$%]?[a-z]?[a-z]?[A-Z][A-Z_]*$/.test(label) || /(?:::|->)[A-Z][A-Z_]+$/.test(label)) {
        sortText = "4" + label;
    } else if (label == "_" || /(?:::|->)_\w+$/.test(label)) {
        sortText = "3" + label;
    } else if (/^\w$/.test(label) || /(?:::|->)\w+$/.test(label)) {
        // Public methods / functions
        sortText = "2";
        // Prioritize '->new'
        if (label.indexOf("->new") != -1) sortText += "1";
        sortText += label;
    } else {
        // Variables and regex mistakes
        sortText = "1" + label;
    }
    return sortText;
}