import { useCallback, useEffect, useState } from "react";
import { useTranslation } from "react-i18next";
import { FileText, ChevronDown, ChevronUp, Plus, Trash2, History } from "lucide-react";
import "./DocumentsView.css";
import "./TaskDocumentsTab.css";
import ReactMarkdown from "react-markdown";
import remarkGfm from "remark-gfm";
import type { ArtifactWithTask, Task, TaskDocument, TaskDocumentRevision } from "@fusion/core";
import { getErrorMessage } from "@fusion/core";
import type { ToastType } from "../hooks/useToast";
import {
  fetchTaskDocuments,
  fetchTaskDocumentRevisions,
  putTaskDocument,
  deleteTaskDocument,
  artifactMediaUrl,
} from "../api";
import { useArtifacts } from "../hooks/useArtifacts";
import { LoadingSpinner } from "./LoadingSpinner";
import { ArtifactMedia, getArtifactTypeLabel } from "./ArtifactMedia";

// Document key validation: alphanumeric, hyphens, underscores, 1-64 chars
const DOCUMENT_KEY_REGEX = /^[a-zA-Z0-9_-]{1,64}$/;
const MAX_CONTENT_PREVIEW = 200;

interface TaskDocumentsTabProps {
  taskId: string;
  addToast: (message: string, type?: ToastType) => void;
  onTaskUpdated?: (task: Task) => void;
  projectId?: string;
  canEdit?: boolean;
}

function formatTimestamp(iso?: string): string {
  if (!iso) return "";
  return new Date(iso).toLocaleString();
}

function getContentPreview(content: string, maxLength: number = MAX_CONTENT_PREVIEW): string {
  if (content.length <= maxLength) return content;
  return content.substring(0, maxLength) + "…";
}

function formatFileSize(bytes: number): string {
  if (bytes < 1024) {
    return `${bytes} B`;
  }

  if (bytes < 1024 * 1024) {
    return `${(bytes / 1024).toFixed(bytes >= 10 * 1024 ? 0 : 1)} KB`;
  }

  return `${(bytes / (1024 * 1024)).toFixed(1)} MB`;
}

interface TaskArtifactCardProps {
  artifact: ArtifactWithTask;
  projectId?: string;
}

function TaskArtifactCard({ artifact, projectId }: TaskArtifactCardProps) {
  const { t } = useTranslation("app");
  const mediaUrl = artifactMediaUrl(artifact.id, projectId);
  const typeLabel = getArtifactTypeLabel(t, artifact.type);
  const preview = artifact.content ? getContentPreview(artifact.content, 320) : artifact.description;
  const title = artifact.title || t("documents.untitledArtifact", "Untitled artifact");

  return (
    <article className="document-card documents-artifact-card" aria-label={t("documents.artifactCardLabel", "Artifact {{title}}", { title })}>
      <div className="documents-artifact-preview">
        <ArtifactMedia artifact={artifact} mediaUrl={mediaUrl} title={title} preview={preview} t={t} />
      </div>
      <div className="documents-artifact-body">
        <div className="documents-artifact-header">
          <span className="documents-artifact-type-badge">{typeLabel}</span>
          <span className="documents-artifact-author">{artifact.authorId}</span>
        </div>
        <h5 className="documents-artifact-title">{title}</h5>
        {artifact.description && <p className="documents-artifact-description">{artifact.description}</p>}
        <div className="documents-artifact-meta">
          <span>{formatTimestamp(artifact.createdAt)}</span>
          {artifact.sizeBytes !== undefined && <span>{formatFileSize(artifact.sizeBytes)}</span>}
        </div>
      </div>
    </article>
  );
}

export function TaskDocumentsTab({
  taskId,
  addToast,
  onTaskUpdated: _onTaskUpdated,
  projectId,
  canEdit = false,
}: TaskDocumentsTabProps) {
  const { t } = useTranslation("app");
  const [documents, setDocuments] = useState<TaskDocument[]>([]);
  const [loading, setLoading] = useState(true);
  const [expandedDocKey, setExpandedDocKey] = useState<string | null>(null);
  const [expandedContent, setExpandedContent] = useState("");
  const [editingDocKey, setEditingDocKey] = useState<string | null>(null);
  const [editContent, setEditContent] = useState("");
  const [showHistory, setShowHistory] = useState<string | null>(null);
  const [revisions, setRevisions] = useState<TaskDocumentRevision[]>([]);
  const [loadingRevisions, setLoadingRevisions] = useState(false);
  const [showCreateForm, setShowCreateForm] = useState(false);
  const [newDocKey, setNewDocKey] = useState("");
  const [newDocContent, setNewDocContent] = useState("");
  const [saving, setSaving] = useState(false);
  const [deletingKey, setDeletingKey] = useState<string | null>(null);
  const [confirmDelete, setConfirmDelete] = useState<string | null>(null);
  const [renderMarkdown, setRenderMarkdown] = useState(false);
  const { artifacts, loading: artifactsLoading, error: artifactsError } = useArtifacts({ projectId, taskId });

  const loadDocuments = useCallback(async () => {
    try {
      const docs = await fetchTaskDocuments(taskId, projectId);
      setDocuments(docs);
    } catch (error) {
      addToast(getErrorMessage(error) || t("taskDocuments.failedToLoad", "Failed to load documents"), "error");
    } finally {
      setLoading(false);
    }
  }, [taskId, projectId, addToast]);

  useEffect(() => {
    void loadDocuments();
  }, [loadDocuments]);

  useEffect(() => {
    if (artifactsError) {
      addToast(artifactsError || t("taskDocuments.failedToLoadArtifacts", "Failed to load artifacts"), "error");
    }
  }, [addToast, artifactsError, t]);

  async function handleExpandDocument(doc: TaskDocument) {
    if (expandedDocKey === doc.key) {
      setExpandedDocKey(null);
      setExpandedContent("");
      setEditingDocKey(null);
      setEditContent("");
      setShowHistory(null);
      setRevisions([]);
      setRenderMarkdown(false);
    } else {
      setExpandedDocKey(doc.key);
      setExpandedContent(doc.content);
      setEditingDocKey(null);
      setEditContent("");
      setShowHistory(null);
      setRevisions([]);
      setRenderMarkdown(false);
    }
  }

  async function handleToggleHistory(docKey: string) {
    if (showHistory === docKey) {
      setShowHistory(null);
      setRevisions([]);
    } else {
      setShowHistory(docKey);
      setLoadingRevisions(true);
      try {
        const revs = await fetchTaskDocumentRevisions(taskId, docKey, projectId);
        setRevisions(revs);
      } catch (error) {
        addToast(getErrorMessage(error) || t("taskDocuments.failedToLoadRevisions", "Failed to load revisions"), "error");
      } finally {
        setLoadingRevisions(false);
      }
    }
  }

  function handleStartEdit() {
    if (expandedDocKey) {
      setEditingDocKey(expandedDocKey);
      setEditContent(expandedContent);
    }
  }

  function handleCancelEdit() {
    setEditingDocKey(null);
    setEditContent("");
  }

  async function handleSaveEdit() {
    if (!editingDocKey || !editContent.trim()) return;
    setSaving(true);
    try {
      await putTaskDocument(taskId, editingDocKey, editContent, {}, projectId);
      setEditingDocKey(null);
      setEditContent("");
      await loadDocuments();
      // Refresh expanded content
      const updated = documents.find((d) => d.key === editingDocKey);
      if (updated) {
        setExpandedContent(updated.content);
      }
      addToast(t("taskDocuments.saved", "Document saved"), "success");
    } catch (error) {
      addToast(getErrorMessage(error) || t("taskDocuments.failedToSave", "Failed to save document"), "error");
    } finally {
      setSaving(false);
    }
  }

  async function handleCreateDocument() {
    const key = newDocKey.trim();
    const content = newDocContent.trim();

    // Validate key
    if (!key) {
      addToast(t("taskDocuments.keyRequired", "Document key is required"), "error");
      return;
    }
    if (!DOCUMENT_KEY_REGEX.test(key)) {
      addToast(t("taskDocuments.invalidKeyFormat", "Invalid key format. Use 1-64 alphanumeric characters, hyphens, or underscores."), "error");
      return;
    }
    if (!content) {
      addToast(t("taskDocuments.contentRequired", "Content is required"), "error");
      return;
    }

    setSaving(true);
    try {
      await putTaskDocument(taskId, key, content, {}, projectId);
      setShowCreateForm(false);
      setNewDocKey("");
      setNewDocContent("");
      await loadDocuments();
      addToast(t("taskDocuments.created", "Document created"), "success");
    } catch (error) {
      addToast(getErrorMessage(error) || t("taskDocuments.failedToCreate", "Failed to create document"), "error");
    } finally {
      setSaving(false);
    }
  }

  async function handleDeleteDocument(key: string) {
    setDeletingKey(key);
    try {
      await deleteTaskDocument(taskId, key, projectId);
      setConfirmDelete(null);
      setDeletingKey(null);
      if (expandedDocKey === key) {
        setExpandedDocKey(null);
        setExpandedContent("");
      }
      if (showHistory === key) {
        setShowHistory(null);
        setRevisions([]);
      }
      await loadDocuments();
      addToast(t("taskDocuments.deleted", "Document deleted"), "success");
    } catch (error) {
      addToast(getErrorMessage(error) || t("taskDocuments.failedToDelete", "Failed to delete document"), "error");
    } finally {
      setDeletingKey(null);
    }
  }

  function handleViewRevision(revision: TaskDocumentRevision) {
    setExpandedContent(revision.content);
    setEditingDocKey(null);
    setEditContent("");
  }

  if (loading || artifactsLoading) {
    return (
      <div className="detail-section">
        <h4>{t("taskDocuments.heading", "Artifacts")}</h4>
        <div className="detail-log-empty"><LoadingSpinner label={t("taskDocuments.loading", "Loading documents and artifacts…")} /></div>
      </div>
    );
  }

  const isEmpty = documents.length === 0 && artifacts.length === 0 && !showCreateForm;

  return (
    <div className="detail-section">
      <h4>{t("taskDocuments.heading", "Artifacts")}</h4>

      {isEmpty && (
        <div className="detail-log-empty">
          {t("taskDocuments.noDocuments", "No documents or artifacts yet.")}
        </div>
      )}

      {/*
       * FNXC:ArtifactRegistry 2026-06-21-21:44:
       * The per-task Artifacts tab must surface both traditional task documents and agent-created media artifacts so users can inspect all task-scoped outputs without leaving the task modal.
       */}
      {artifacts.length > 0 && (
        <section className="task-artifacts-section" aria-labelledby="task-artifacts-heading">
          <div className="task-artifacts-section-header">
            <h5 id="task-artifacts-heading">{t("taskDocuments.artifactsSubheading", "Media artifacts")}</h5>
            <span className="task-artifacts-section-count">{t("taskDocuments.artifactCount", "{{count}} artifact{{plural}}", { count: artifacts.length, plural: artifacts.length === 1 ? "" : "s" })}</span>
          </div>
          <div className="documents-artifact-gallery documents-artifact-gallery--mobile task-artifacts-gallery">
            {artifacts.map((artifact) => (
              <TaskArtifactCard key={artifact.id} artifact={artifact} projectId={projectId} />
            ))}
          </div>
        </section>
      )}

      <section className="task-documents-section" aria-labelledby="task-documents-heading">
        <div className="task-artifacts-section-header">
          <h5 id="task-documents-heading">{t("taskDocuments.documentsSubheading", "Task documents")}</h5>
          {documents.length > 0 && (
            <span className="task-artifacts-section-count">{t("taskDocuments.documentCount", "{{count}} document{{plural}}", { count: documents.length, plural: documents.length === 1 ? "" : "s" })}</span>
          )}
        </div>

      {/* Create Form */}
      {showCreateForm && (
        <div className="task-document-create-form">
          <h5>{t("taskDocuments.newDocumentTitle", "New Document")}</h5>
          <div className="form-group">
            <label htmlFor="doc-key">{t("taskDocuments.keyLabel", "Key")}</label>
            <input
              id="doc-key"
              type="text"
              className="task-document-key-input"
              value={newDocKey}
              onChange={(e) => setNewDocKey(e.target.value)}
              placeholder={t("taskDocuments.keyPlaceholder", "e.g., plan, notes, research")}
              disabled={saving}
            />
            <span className="form-hint">{t("taskDocuments.keyHint", "Alphanumeric, hyphens, underscores (1-64 chars)")}</span>
          </div>
          <div className="form-group">
            <label htmlFor="doc-content">{t("taskDocuments.contentLabel", "Content")}</label>
            <textarea
              id="doc-content"
              value={newDocContent}
              onChange={(e) => setNewDocContent(e.target.value)}
              rows={6}
              placeholder={t("taskDocuments.contentPlaceholder", "Enter document content…")}
              disabled={saving}
            />
          </div>
          <div className="form-actions">
            <button
              className="btn btn-sm"
              onClick={() => {
                setShowCreateForm(false);
                setNewDocKey("");
                setNewDocContent("");
              }}
              disabled={saving}
            >
              {t("taskDocuments.cancel", "Cancel")}
            </button>
            <button
              className="btn btn-primary btn-sm"
              onClick={() => void handleCreateDocument()}
              disabled={saving || !newDocKey.trim() || !newDocContent.trim()}
            >
              {saving ? t("taskDocuments.creating", "Creating…") : t("taskDocuments.create", "Create")}
            </button>
          </div>
        </div>
      )}

      {/* Document List */}
      {documents.length === 0 && !showCreateForm ? (
        !isEmpty && (
          <div className="detail-log-empty">
            {t("taskDocuments.noTaskDocuments", "No task documents yet.")}
          </div>
        )
      ) : (
        <div className="task-documents-list">
          {documents.map((doc) => (
            <div key={doc.key} className="task-document-card">
              <div className="task-document-card-header">
                <div className="task-document-card-title">
                  <FileText size={14} />
                  <span className="task-document-key">{doc.key}</span>
                  <span className="task-document-revision-badge">v{doc.revision}</span>
                </div>
                <div className="task-document-meta">
                  <span className="task-document-author">{doc.author}</span>
                  <span className="task-document-timestamp">{formatTimestamp(doc.updatedAt || doc.createdAt)}</span>
                </div>
              </div>

              {/* Expanded Content View */}
              {expandedDocKey === doc.key && editingDocKey !== doc.key && (
                <>
                  <div className="task-document-content-header">
                    <button
                      className="btn btn-sm document-mode-toggle"
                      onClick={() => setRenderMarkdown((prev) => !prev)}
                      aria-label={renderMarkdown ? t("taskDocuments.switchToPlainText", "Switch to plain text") : t("taskDocuments.switchToMarkdown", "Switch to markdown")}
                      aria-pressed={renderMarkdown}
                      title={renderMarkdown ? t("taskDocuments.switchToPlainText", "Switch to plain text") : t("taskDocuments.switchToMarkdown", "Switch to markdown")}
                    >
                      {renderMarkdown ? t("taskDocuments.modeMarkdown", "Markdown") : t("taskDocuments.modePlain", "Plain")}
                    </button>
                  </div>
                  <div className="task-document-content">
                    {renderMarkdown ? (
                      <div className="task-document-content-markdown">
                        <div className="markdown-body">
                          <ReactMarkdown remarkPlugins={[remarkGfm]}>{expandedContent}</ReactMarkdown>
                        </div>
                      </div>
                    ) : (
                      <pre className="task-document-content-text">{expandedContent}</pre>
                    )}
                  </div>

                  {/* Revision History */}
                  {showHistory === doc.key && (
                    <div className="task-document-revisions">
                      <h5>{t("taskDocuments.revisionHistory", "Revision History")}</h5>
                      {loadingRevisions ? (
                        <div className="detail-log-empty"><LoadingSpinner label={t("taskDocuments.loadingRevisions", "Loading…")} /></div>
                      ) : revisions.length <= 1 ? (
                        <div className="detail-log-empty">{t("taskDocuments.noPreviousRevisions", "No previous revisions.")}</div>
                      ) : (
                        <div className="task-document-revision-list">
                          {revisions
                            .filter((r) => r.revision < doc.revision)
                            .sort((a, b) => b.revision - a.revision)
                            .map((revision) => (
                              <div
                                key={revision.id}
                                className="task-document-revision-item"
                                onClick={() => handleViewRevision(revision)}
                              >
                                <div className="revision-header">
                                  <span className="revision-badge">v{revision.revision}</span>
                                  <span className="revision-author">{revision.author}</span>
                                  <span className="revision-timestamp">{formatTimestamp(revision.createdAt)}</span>
                                </div>
                                <div className="revision-preview">{getContentPreview(revision.content, 100)}</div>
                              </div>
                            ))}
                        </div>
                      )}
                    </div>
                  )}
                </>
              )}

              {/* Editing View */}
              {editingDocKey === doc.key && (
                <div className="task-document-edit-form">
                  <textarea
                    value={editContent}
                    onChange={(e) => setEditContent(e.target.value)}
                    rows={10}
                    disabled={saving}
                  />
                  <div className="form-actions">
                    <button className="btn btn-sm" onClick={handleCancelEdit} disabled={saving}>
                      {t("taskDocuments.cancel", "Cancel")}
                    </button>
                    <button
                      className="btn btn-primary btn-sm"
                      onClick={() => void handleSaveEdit()}
                      disabled={saving || !editContent.trim()}
                    >
                      {saving ? t("taskDocuments.saving", "Saving…") : t("taskDocuments.save", "Save")}
                    </button>
                  </div>
                </div>
              )}

              {/* Actions */}
              <div className="task-document-actions">
                <button
                  className="btn btn-sm"
                  onClick={() => void handleExpandDocument(doc)}
                >
                  {expandedDocKey === doc.key ? (
                    <>
                      <ChevronUp size={14} /> {t("taskDocuments.collapse", "Collapse")}
                    </>
                  ) : (
                    <>
                      <ChevronDown size={14} /> {t("taskDocuments.expand", "Expand")}
                    </>
                  )}
                </button>

                {expandedDocKey === doc.key && (
                  <>
                    <button
                      className="btn btn-sm"
                      onClick={() => void handleToggleHistory(doc.key)}
                    >
                      <History size={14} /> {t("taskDocuments.history", "History")}
                    </button>

                    {canEdit && editingDocKey !== doc.key && (
                      <button className="btn btn-sm" onClick={handleStartEdit}>
                        {t("taskDocuments.edit", "Edit")}
                      </button>
                    )}

                    {canEdit && (
                      confirmDelete === doc.key ? (
                        <div className="confirm-delete-actions">
                          <span>{t("taskDocuments.deleteConfirm", "Delete?")}</span>
                          <button
                            className="btn btn-danger btn-sm"
                            onClick={() => void handleDeleteDocument(doc.key)}
                            disabled={deletingKey === doc.key}
                          >
                            {deletingKey === doc.key ? "…" : t("taskDocuments.yes", "Yes")}
                          </button>
                          <button
                            className="btn btn-sm"
                            onClick={() => setConfirmDelete(null)}
                            disabled={deletingKey === doc.key}
                          >
                            {t("taskDocuments.no", "No")}
                          </button>
                        </div>
                      ) : (
                        <button
                          className="btn btn-danger btn-sm"
                          onClick={() => setConfirmDelete(doc.key)}
                        >
                          <Trash2 size={14} />
                        </button>
                      )
                    )}
                  </>
                )}
              </div>
            </div>
          ))}
        </div>
      )}

      {/* New Document Button */}
      {canEdit && !showCreateForm && (
        <button
          className="btn btn-sm task-document-new-btn"
          onClick={() => setShowCreateForm(true)}
        >
          <Plus size={14} /> {t("taskDocuments.newDocumentButton", "New Document")}
        </button>
      )}
      </section>
    </div>
  );
}