/**
 * LangChain Integration Pattern Tests
 *
 * Tests that validate the patterns documented in LANGCHAIN_INTEGRATION.md
 * without requiring actual LangChain dependencies.
 */

import { describe, it, expect } from 'vitest';

/**
 * Types that mirror the expected tool interface from LangChain.
 */
interface MockTool {
  name: string;
  description: string;
  inputSchema: Record<string, unknown>;
}

/**
 * Mock Flywheel read tools (subset for testing).
 */
const mockFlywheelTools: MockTool[] = [
  {
    name: 'get_section_content',
    description: 'Get content of a specific section from a note',
    inputSchema: {
      type: 'object',
      properties: {
        path: { type: 'string', description: 'Path to the note' },
        heading: { type: 'string', description: 'Section heading' },
      },
      required: ['path', 'heading'],
    },
  },
  {
    name: 'get_backlinks',
    description: 'Get notes that link to this note',
    inputSchema: {
      type: 'object',
      properties: {
        path: { type: 'string', description: 'Path to the note' },
      },
      required: ['path'],
    },
  },
  {
    name: 'search_notes',
    description: 'Search notes by content or metadata',
    inputSchema: {
      type: 'object',
      properties: {
        query: { type: 'string', description: 'Search query' },
        limit: { type: 'number', description: 'Max results' },
      },
      required: ['query'],
    },
  },
  {
    name: 'get_note_metadata',
    description: 'Get note frontmatter and metadata',
    inputSchema: {
      type: 'object',
      properties: {
        path: { type: 'string', description: 'Path to the note' },
      },
      required: ['path'],
    },
  },
];

/**
 * Mock Flywheel Memory write tools (subset for testing).
 */
const mockWriteTools: MockTool[] = [
  {
    name: 'vault_add_to_section',
    description: 'Add content to a section in a note',
    inputSchema: {
      type: 'object',
      properties: {
        path: { type: 'string' },
        section: { type: 'string' },
        content: { type: 'string' },
        format: { type: 'string', enum: ['bullet', 'task', 'timestamp-bullet', 'plain'] },
        position: { type: 'string', enum: ['append', 'prepend'] },
        commit: { type: 'boolean' },
      },
      required: ['path', 'section', 'content'],
    },
  },
  {
    name: 'vault_add_task',
    description: 'Add a task to a section',
    inputSchema: {
      type: 'object',
      properties: {
        path: { type: 'string' },
        section: { type: 'string' },
        task: { type: 'string' },
        position: { type: 'string', enum: ['append', 'prepend'] },
        commit: { type: 'boolean' },
      },
      required: ['path', 'section', 'task'],
    },
  },
  {
    name: 'vault_toggle_task',
    description: 'Toggle a task checkbox',
    inputSchema: {
      type: 'object',
      properties: {
        path: { type: 'string' },
        task: { type: 'string' },
        section: { type: 'string' },
        commit: { type: 'boolean' },
      },
      required: ['path', 'task'],
    },
  },
  {
    name: 'vault_update_frontmatter',
    description: 'Update note frontmatter',
    inputSchema: {
      type: 'object',
      properties: {
        path: { type: 'string' },
        frontmatter: { type: 'object' },
        commit: { type: 'boolean' },
      },
      required: ['path', 'frontmatter'],
    },
  },
];

/**
 * Simulate prefixed tools from MultiServerMCPClient.
 */
function prefixTools(serverName: string, tools: MockTool[]): MockTool[] {
  return tools.map(tool => ({
    ...tool,
    name: `${serverName}__${tool.name}`,
  }));
}

describe('LangChain Tool Schema Patterns', () => {
  const flywheelPrefixed = prefixTools('flywheel', mockFlywheelTools);
  const writePrefixed = prefixTools('flywheel-memory', mockWriteTools);
  const allPrefixed = [...flywheelPrefixed, ...writePrefixed];

  describe('tool schema structure', () => {
    it('should have name, description, and inputSchema for each tool', () => {
      for (const tool of allPrefixed) {
        expect(tool.name).toBeDefined();
        expect(typeof tool.name).toBe('string');
        expect(tool.description).toBeDefined();
        expect(typeof tool.description).toBe('string');
        expect(tool.inputSchema).toBeDefined();
        expect(typeof tool.inputSchema).toBe('object');
      }
    });

    it('should have valid inputSchema with type object', () => {
      for (const tool of allPrefixed) {
        expect(tool.inputSchema.type).toBe('object');
        expect(tool.inputSchema.properties).toBeDefined();
      }
    });

    it('should have required array in inputSchema', () => {
      for (const tool of allPrefixed) {
        expect(Array.isArray(tool.inputSchema.required)).toBe(true);
      }
    });
  });

  describe('read tools have path parameter', () => {
    it('should have path in required for read tools', () => {
      for (const tool of flywheelPrefixed) {
        // Most read tools require a path (except search which requires query)
        const required = tool.inputSchema.required as string[];
        const hasPathOrQuery = required.includes('path') || required.includes('query');
        expect(hasPathOrQuery).toBe(true);
      }
    });
  });

  describe('write tools have common parameters', () => {
    it('should have path in required for write tools', () => {
      for (const tool of writePrefixed) {
        const required = tool.inputSchema.required as string[];
        expect(required.includes('path')).toBe(true);
      }
    });

    it('should have commit as optional boolean', () => {
      for (const tool of writePrefixed) {
        const properties = tool.inputSchema.properties as Record<string, { type?: string }>;
        if (properties.commit) {
          expect(properties.commit.type).toBe('boolean');
        }
      }
    });
  });
});

describe('LangChain Workflow Patterns', () => {
  describe('read-before-write pattern', () => {
    // Simulate a workflow that reads then writes
    interface WorkflowStep {
      tool: string;
      isRead: boolean;
      purpose: string;
    }

    const meetingToTasksWorkflow: WorkflowStep[] = [
      { tool: 'flywheel__get_section_content', isRead: true, purpose: 'Read meeting action items' },
      { tool: 'flywheel__get_backlinks', isRead: true, purpose: 'Find related projects' },
      { tool: 'flywheel-memory__vault_add_task', isRead: false, purpose: 'Add tasks to daily note' },
      { tool: 'flywheel-memory__vault_add_to_section', isRead: false, purpose: 'Update project log' },
      { tool: 'flywheel__get_section_content', isRead: true, purpose: 'Verify changes' },
    ];

    it('should start with read operations', () => {
      const firstStep = meetingToTasksWorkflow[0];
      expect(firstStep.isRead).toBe(true);
      expect(firstStep.tool.startsWith('flywheel__')).toBe(true);
    });

    it('should have reads before writes', () => {
      const readSteps = meetingToTasksWorkflow.filter(s => s.isRead);
      const writeSteps = meetingToTasksWorkflow.filter(s => !s.isRead);

      // At least one read before first write
      const firstWriteIndex = meetingToTasksWorkflow.findIndex(s => !s.isRead);
      const readsBeforeWrite = meetingToTasksWorkflow.slice(0, firstWriteIndex).filter(s => s.isRead);

      expect(readsBeforeWrite.length).toBeGreaterThan(0);
      expect(readSteps.length).toBeGreaterThan(0);
      expect(writeSteps.length).toBeGreaterThan(0);
    });

    it('should end with verification read', () => {
      const lastStep = meetingToTasksWorkflow[meetingToTasksWorkflow.length - 1];
      expect(lastStep.isRead).toBe(true);
      expect(lastStep.purpose).toContain('Verify');
    });
  });

  describe('multi-agent coordination pattern', () => {
    interface AgentConfig {
      name: string;
      tools: string[];
      canRead: boolean;
      canWrite: boolean;
    }

    function createAgentConfig(name: string, toolFilter: (t: string) => boolean): AgentConfig {
      const allTools = [
        'flywheel__get_section_content',
        'flywheel__get_backlinks',
        'flywheel-memory__vault_add_task',
        'flywheel-memory__vault_add_to_section',
      ];

      const tools = allTools.filter(toolFilter);
      const canRead = tools.some(t => t.startsWith('flywheel__'));
      const canWrite = tools.some(t => t.startsWith('flywheel-memory__'));

      return { name, tools, canRead, canWrite };
    }

    it('should create reader agent with only read capabilities', () => {
      const reader = createAgentConfig('reader', t => t.startsWith('flywheel__'));

      expect(reader.canRead).toBe(true);
      expect(reader.canWrite).toBe(false);
      expect(reader.tools.every(t => t.startsWith('flywheel__'))).toBe(true);
    });

    it('should create writer agent with only write capabilities', () => {
      const writer = createAgentConfig('writer', t => t.startsWith('flywheel-memory__'));

      expect(writer.canRead).toBe(false);
      expect(writer.canWrite).toBe(true);
      expect(writer.tools.every(t => t.startsWith('flywheel-memory__'))).toBe(true);
    });

    it('should allow combined agent with both capabilities', () => {
      const combined = createAgentConfig('combined', () => true);

      expect(combined.canRead).toBe(true);
      expect(combined.canWrite).toBe(true);
      expect(combined.tools.length).toBe(4);
    });
  });
});

describe('LangChain Permission Patterns', () => {
  describe('permission escalation pattern', () => {
    // Simulate gradual permission approval
    const permissionStages = [
      {
        stage: 1,
        name: 'Read Only',
        allowed: ['mcp__flywheel__*'],
        denied: ['mcp__flywheel-memory__*'],
      },
      {
        stage: 2,
        name: 'Safe Writes',
        allowed: [
          'mcp__flywheel__*',
          'mcp__flywheel-memory__vault_add_task',
          'mcp__flywheel-memory__vault_toggle_task',
        ],
        denied: ['mcp__flywheel-memory__vault_delete_note'],
      },
      {
        stage: 3,
        name: 'Full Writes',
        allowed: [
          'mcp__flywheel__*',
          'mcp__flywheel-memory__*',
        ],
        denied: ['mcp__flywheel-memory__vault_delete_note'],
      },
    ];

    it('should start with read-only permissions', () => {
      const stage1 = permissionStages[0];
      expect(stage1.allowed).toContain('mcp__flywheel__*');
      expect(stage1.denied).toContain('mcp__flywheel-memory__*');
    });

    it('should gradually expand write permissions', () => {
      const stage2 = permissionStages[1];
      expect(stage2.allowed).toContain('mcp__flywheel-memory__vault_add_task');
      expect(stage2.allowed).toContain('mcp__flywheel-memory__vault_toggle_task');
    });

    it('should always deny destructive operations explicitly or by wildcard', () => {
      for (const stage of permissionStages) {
        // Either explicitly denied or covered by wildcard
        const explicitlyDenied = stage.denied.includes('mcp__flywheel-memory__vault_delete_note');
        const deniedByWildcard = stage.denied.includes('mcp__flywheel-memory__*');
        expect(explicitlyDenied || deniedByWildcard).toBe(true);
      }
    });
  });
});

describe('LangChain Tool Invocation Patterns', () => {
  describe('tool argument validation', () => {
    interface ToolCall {
      tool: string;
      args: Record<string, unknown>;
    }

    function validateToolCall(call: ToolCall, schema: MockTool): { valid: boolean; errors: string[] } {
      const errors: string[] = [];
      const required = schema.inputSchema.required as string[];

      for (const param of required) {
        if (!(param in call.args)) {
          errors.push(`Missing required parameter: ${param}`);
        }
      }

      return { valid: errors.length === 0, errors };
    }

    it('should validate required parameters', () => {
      const tool = mockWriteTools.find(t => t.name === 'vault_add_to_section')!;

      const validCall: ToolCall = {
        tool: 'vault_add_to_section',
        args: { path: 'test.md', section: 'Log', content: 'Entry' },
      };

      const invalidCall: ToolCall = {
        tool: 'vault_add_to_section',
        args: { path: 'test.md' }, // missing section and content
      };

      expect(validateToolCall(validCall, tool).valid).toBe(true);
      expect(validateToolCall(invalidCall, tool).valid).toBe(false);
      expect(validateToolCall(invalidCall, tool).errors).toContain('Missing required parameter: section');
      expect(validateToolCall(invalidCall, tool).errors).toContain('Missing required parameter: content');
    });
  });

  describe('tool result handling', () => {
    interface MutationResult {
      success: boolean;
      message: string;
      path?: string;
      preview?: string;
      gitCommit?: string;
      undoAvailable?: boolean;
    }

    it('should expect standard MutationResult from Write tools', () => {
      const successResult: MutationResult = {
        success: true,
        message: 'Added content to section "Log"',
        path: 'daily-notes/2026-02-10.md',
        preview: '- **10:30** New entry\n→ [[Project]]',
        gitCommit: 'abc123f',
        undoAvailable: true,
      };

      expect(successResult.success).toBe(true);
      expect(successResult.path).toBeDefined();
      expect(successResult.preview).toBeDefined();
    });

    it('should handle failure results', () => {
      const failureResult: MutationResult = {
        success: false,
        message: "Section 'Log' not found. Available sections: Tasks, Notes",
      };

      expect(failureResult.success).toBe(false);
      expect(failureResult.message).toContain('not found');
    });

    it('should handle git commit failures gracefully', () => {
      const partialResult: MutationResult = {
        success: true, // File was mutated
        message: 'Added content to section',
        path: 'test.md',
        // gitCommit is undefined (commit failed)
      };

      // File was saved even though commit failed
      expect(partialResult.success).toBe(true);
      expect(partialResult.gitCommit).toBeUndefined();
    });
  });
});
