import { ViewPlugin, ViewUpdate } from '@codemirror/view';
import { Extension } from '@codemirror/state';
import { categoryForType, LogfireSettings } from '../types';
import { EventBus } from '../core/event-bus';
import { SessionManager } from '../core/session-manager';

interface PendingChange {
  inserted: number;
  deleted: number;
  from: number;
  to: number;
}

export class EditorCollector {
  constructor(
    private eventBus: EventBus,
    private sessionManager: SessionManager,
    private settings: LogfireSettings,
    private shouldTrack: (path: string) => boolean,
    private getActiveFilePath: () => string | null,
  ) {}

  createExtension(): Extension {
    const collector = this;

    return ViewPlugin.fromClass(
      class {
        private pendingChanges: PendingChange[] = [];
        private debounceTimer: ReturnType<typeof setTimeout> | null = null;
        private batchStartTime = 0;

        update(update: ViewUpdate): void {
          if (!update.docChanged) return;
          if (!collector.settings.tracking.editorChanges) return;

          const filePath = collector.getActiveFilePath();
          if (!filePath || !collector.shouldTrack(filePath)) return;

          if (this.pendingChanges.length === 0) {
            this.batchStartTime = Date.now();
          }

          update.changes.iterChanges((fromA, toA, _fromB, toB, inserted) => {
            this.pendingChanges.push({
              inserted: inserted.length,
              deleted: toA - fromA,
              from: fromA,
              to: toB,
            });
          });

          if (this.debounceTimer !== null) {
            clearTimeout(this.debounceTimer);
          }
          this.debounceTimer = setTimeout(
            () => this.flush(filePath),
            collector.settings.advanced.debounceMs,
          );
        }

        private flush(filePath: string): void {
          if (this.pendingChanges.length === 0) return;

          const changes = this.pendingChanges.splice(0);
          const duration = Date.now() - this.batchStartTime;

          let insertedChars = 0;
          let deletedChars = 0;
          let rangeStart = Infinity;
          let rangeEnd = 0;

          for (const c of changes) {
            insertedChars += c.inserted;
            deletedChars += c.deleted;
            if (c.from < rangeStart) rangeStart = c.from;
            if (c.to > rangeEnd) rangeEnd = c.to;
          }

          collector.emitChange(filePath, {
            insertedChars,
            deletedChars,
            rangeStart: rangeStart === Infinity ? 0 : rangeStart,
            rangeEnd,
            duration,
          });
        }

        destroy(): void {
          if (this.debounceTimer !== null) {
            clearTimeout(this.debounceTimer);
          }
        }
      },
    );
  }

  private emitChange(source: string, payload: Record<string, unknown>): void {
    this.eventBus.emit({
      id: crypto.randomUUID(),
      timestamp: Date.now(),
      type: 'editor:change',
      category: categoryForType('editor:change'),
      source,
      payload,
      session: this.sessionManager.currentSessionId,
    });
  }
}