import * as monaco from 'monaco-editor';
import type { editor } from 'monaco-editor';
import { parse } from '../parser';
import { locate } from '../parser/locate';
import type { LogQLFieldCompletionContext, LogQLLanguage, VendorConfig } from '../types';
import { buildCompletions } from './completions';
import type { MutableRefObject } from 'react';
import { getHistoryCompletionItems } from '../history';

export interface ProviderOptions {
  vendor: VendorConfig;
  getVariables: () => string[];
  getLanguage: () => LogQLLanguage;
  getHistoryKey: () => string | undefined;
  getCanShowHistory: () => boolean;
  getFetchFieldNames: () => ((ctx: LogQLFieldCompletionContext) => Promise<string[]>) | undefined;
  getFetchFieldValues: () => ((fieldName: string, ctx: LogQLFieldCompletionContext) => Promise<string[]>) | undefined;
  editorRef: MutableRefObject<editor.IStandaloneCodeEditor | null>;
}

export function getLogQLCompletionProvider(opts: ProviderOptions): monaco.languages.CompletionItemProvider {
  return {
    triggerCharacters: ['$', ':', '=', '|', '(', ' ', ',', '.'],
    provideCompletionItems: async (model, position) => {
      // Only serve requests from this editor's own model
      if (opts.editorRef.current?.getModel()?.id !== model.id) {
        return { suggestions: [] };
      }
      const value = model.getValue();
      const offset = model.getOffsetAt(position);
      const { ast, tokens } = parse(value);
      const situation = locate(offset, ast, tokens);

      const startPos = model.getPositionAt(situation.replaceRange.start);
      const endPos = model.getPositionAt(situation.replaceRange.end);
      const range: monaco.IRange = {
        startLineNumber: startPos.lineNumber,
        startColumn: startPos.column,
        endLineNumber: endPos.lineNumber,
        endColumn: endPos.column,
      };
      const isHistoryContext =
        opts.getCanShowHistory() &&
        situation.section === 'search' &&
        offset === value.length;
      const fullRange: monaco.IRange = {
        startLineNumber: 1,
        startColumn: 1,
        endLineNumber: position.lineNumber,
        endColumn: position.column,
      };

      const suggestions = await buildCompletions({
        vendor: opts.vendor,
        situation,
        range,
        variables: opts.getVariables(),
        language: opts.getLanguage(),
        history: isHistoryContext ? getHistoryCompletionItems(opts.getHistoryKey()) : [],
        historyRange: fullRange,
        fetchFieldNames: opts.getFetchFieldNames(),
        fetchFieldValues: opts.getFetchFieldValues(),
      });

      return { suggestions };
    },
  };
}