# CAN Service API Reference

**Base URL:** `http://localhost:3210`
**API Prefix:** `/api/v1/can/0`
**Content-Type:** `application/json` (all responses are JSON)

> The `0` in the path is the `can_id`. MVP supports only container `0`.

---

## Quick Start

```bash
# Start the server
cargo run

# Store a file
curl -X POST http://localhost:3210/api/v1/can/0/ingest \
  -F "file=@photo.jpg" \
  -F "tags=vacation,beach" \
  -F "description=Summer trip"

# Store data (no file needed)
curl -X POST http://localhost:3210/api/v1/can/0/ingest/data \
  -H "Content-Type: application/json" \
  -d '{"data": {"sensor": "temp", "value": 22.5}, "tags": "iot,sensor"}'

# List everything
curl http://localhost:3210/api/v1/can/0/list

# Search by tag
curl "http://localhost:3210/api/v1/can/0/search?tags=vacation"
```

---

## Response Envelope

All responses use a standard wrapper:

```json
// Success
{
  "status": "success",
  "data": { ... }
}

// Error
{
  "status": "error",
  "error": "Human-readable error message"
}
```

**HTTP Status Codes:**
| Code | Meaning |
|------|---------|
| 200 | Success |
| 400 | Bad request (missing/invalid parameters) |
| 404 | Asset not found |
| 500 | Internal error / corrupted asset |

---

## Endpoints

### 1. Ingest File (Multipart)

Upload a binary file with optional metadata.

```
POST /api/v1/can/0/ingest
Content-Type: multipart/form-data
```

**Form Fields:**

| Field | Type | Required | Description |
|-------|------|----------|-------------|
| `file` | Binary | **Yes** | The file to store |
| `mime_type` | String | No | Override MIME type (auto-detected from filename if omitted) |
| `human_file_name` | String | No | Logical filename (e.g. `report.pdf`) |
| `human_readable_path` | String | No | Logical folder path (e.g. `/docs/reports/`) |
| `application` | String | No | Application that produced this file |
| `user` | String | No | User or agent identity |
| `tags` | String | No | Comma-separated tags (e.g. `finance,Q4,report`) |
| `description` | String | No | Human-readable description |

**Response:**

```json
{
  "status": "success",
  "data": {
    "timestamp": 1773014400123,
    "hash": "a3b2c4d5e6f7...",
    "filename": "1773014400123_a3b2c4d5e6f7_finance_Q4.pdf"
  }
}
```

**Example:**

```bash
curl -X POST http://localhost:3210/api/v1/can/0/ingest \
  -F "file=@quarterly_report.pdf" \
  -F "application=WebUI" \
  -F "user=jason" \
  -F "tags=finance,Q4,report" \
  -F "description=Q4 2025 financial report" \
  -F "human_file_name=quarterly_report.pdf" \
  -F "human_readable_path=/finance/reports/"
```

---

### 2. Ingest Data (JSON)

Store any JSON value directly -- no multipart needed. Designed for agents and programmatic use.

```
POST /api/v1/can/0/ingest/data
Content-Type: application/json
```

**JSON Body:**

| Field | Type | Required | Default | Description |
|-------|------|----------|---------|-------------|
| `data` | Any JSON | **Yes** | -- | The payload to store. Object, array, string, number, boolean, or null. |
| `mime_type` | String | No | `application/json` | Override MIME type (e.g. `text/plain` to store as `.txt`) |
| `human_file_name` | String | No | | Logical filename |
| `human_readable_path` | String | No | | Logical folder path |
| `application` | String | No | | Application/agent that produced this data |
| `user` | String | No | | User or agent identity |
| `tags` | String | No | | Comma-separated tags |
| `description` | String | No | | Human-readable description |

The `data` field is serialized to pretty-printed JSON and stored as a `.json` file (or `.txt` etc. if you override `mime_type`).

**Response:** Same as file ingest.

**Examples:**

```bash
# Minimal -- just dump an object
curl -X POST http://localhost:3210/api/v1/can/0/ingest/data \
  -H "Content-Type: application/json" \
  -d '{"data": {"key": "value"}}'

# Agent saving structured output
curl -X POST http://localhost:3210/api/v1/can/0/ingest/data \
  -H "Content-Type: application/json" \
  -d '{
    "data": {
      "agent_id": "planner-v2",
      "session": "abc-123",
      "steps": ["research", "outline", "draft"]
    },
    "application": "AgentOrchestrator",
    "user": "planner_agent",
    "tags": "agent,plan,session",
    "description": "Planning output for session abc-123",
    "human_file_name": "plan_output.json",
    "human_readable_path": "/agents/planner/"
  }'

# Store a plain string
curl -X POST http://localhost:3210/api/v1/can/0/ingest/data \
  -H "Content-Type: application/json" \
  -d '{"data": "Log: task completed at 14:30", "tags": "log"}'

# Store an array
curl -X POST http://localhost:3210/api/v1/can/0/ingest/data \
  -H "Content-Type: application/json" \
  -d '{"data": [1, 2, 3, "four"], "tags": "test"}'

# Store as plain text instead of JSON
curl -X POST http://localhost:3210/api/v1/can/0/ingest/data \
  -H "Content-Type: application/json" \
  -d '{"data": "plain text content", "mime_type": "text/plain"}'
```

---

### 3. Retrieve Asset

Download the physical file by its hash.

```
GET /api/v1/can/0/asset/{hash}
```

**Path Parameters:**

| Param | Type | Description |
|-------|------|-------------|
| `hash` | String | The SHA-256 hash returned from ingest |

**Response:** Raw file bytes with headers:
- `Content-Type` set to the asset's MIME type
- `Content-Disposition: attachment; filename="<human_filename>"`

Returns `500` if the asset is flagged as corrupted.

**Example:**

```bash
curl -o output.pdf http://localhost:3210/api/v1/can/0/asset/a3b2c4d5e6f7...
```

---

### 4. Get Asset Metadata

Retrieve all metadata for an asset without downloading the file.

```
GET /api/v1/can/0/asset/{hash}/meta
```

**Response:**

```json
{
  "status": "success",
  "data": {
    "hash": "a3b2c4d5e6f7...",
    "mime_type": "application/pdf",
    "application": "WebUI",
    "user": "jason",
    "tags": ["finance", "Q4", "report"],
    "description": "Q4 2025 financial report",
    "human_filename": "quarterly_report.pdf",
    "human_path": "/finance/reports/",
    "timestamp": 1773014400123,
    "is_trashed": false,
    "is_corrupted": false
  }
}
```

---

### 5. Update Metadata

Modify tags and/or description for an existing asset. The physical file is unchanged.

```
PATCH /api/v1/can/0/asset/{hash}
Content-Type: application/json
```

**JSON Body:**

| Field | Type | Required | Description |
|-------|------|----------|-------------|
| `tags` | String[] | No | New tag list (replaces all existing tags) |
| `description` | String | No | New description |

Both fields are optional. Only provided fields are updated.

**Example:**

```bash
curl -X PATCH http://localhost:3210/api/v1/can/0/asset/a3b2c4d5e6f7... \
  -H "Content-Type: application/json" \
  -d '{
    "tags": ["finance", "Q4", "report", "reviewed"],
    "description": "Q4 2025 report - reviewed by CFO"
  }'
```

**Response:**

```json
{
  "status": "success",
  "data": "updated"
}
```

---

### 6. List Assets

Paginated listing of all assets with optional filtering.

```
GET /api/v1/can/0/list
```

**Query Parameters:**

| Param | Type | Default | Description |
|-------|------|---------|-------------|
| `limit` | Integer | `50` | Page size |
| `offset` | Integer | `0` | Starting position |
| `offset_time` | Integer | -- | Epoch ms cursor. Lists items strictly before/after this timestamp (based on `order`). Faster than offset for large datasets. |
| `order` | String | `desc` | Sort direction: `asc` or `desc` (by timestamp) |
| `application` | String | -- | Filter to assets from this application |
| `include_trashed` | Boolean | `false` | Include soft-deleted assets |
| `include_corrupted` | Boolean | `false` | Include corrupted assets |

**Response:**

```json
{
  "status": "success",
  "data": {
    "items": [
      {
        "hash": "a3b2...",
        "mime_type": "application/pdf",
        "application": "WebUI",
        "user": "jason",
        "tags": ["finance"],
        "description": "...",
        "human_filename": "report.pdf",
        "human_path": "/docs/",
        "timestamp": 1773014400123,
        "is_trashed": false,
        "is_corrupted": false
      }
    ],
    "pagination": {
      "limit": 50,
      "offset": 0,
      "total": 142
    }
  }
}
```

**Examples:**

```bash
# First page, 10 items
curl "http://localhost:3210/api/v1/can/0/list?limit=10"

# Second page
curl "http://localhost:3210/api/v1/can/0/list?limit=10&offset=10"

# Only assets from a specific app, oldest first
curl "http://localhost:3210/api/v1/can/0/list?application=IoTAgent&order=asc"

# Include trashed assets
curl "http://localhost:3210/api/v1/can/0/list?include_trashed=true"
```

---

### 7. Search Assets

Search with multiple filters. All filters are AND-combined.

```
GET /api/v1/can/0/search
```

**Query Parameters:**

| Param | Type | Default | Description |
|-------|------|---------|-------------|
| `hash` | String | -- | Exact hash or prefix match (e.g. `a3b2` matches `a3b2c4d5...`) |
| `start_time` | Integer | -- | Epoch ms lower bound (inclusive) |
| `end_time` | Integer | -- | Epoch ms upper bound (inclusive) |
| `tags` | String | -- | Comma-separated. AND logic: asset must have **all** specified tags. |
| `mime_type` | String | -- | Exact MIME type match (e.g. `image/jpeg`) |
| `user` | String | -- | Exact user/agent identity match |
| `application` | String | -- | Exact application match |
| `limit` | Integer | `50` | Page size |
| `offset` | Integer | `0` | Starting position |
| `order` | String | `desc` | Sort direction: `asc` or `desc` |
| `include_trashed` | Boolean | `false` | Include soft-deleted assets |
| `include_corrupted` | Boolean | `false` | Include corrupted assets |

**Response:** Same structure as List (items + pagination).

**Examples:**

```bash
# Find by hash prefix
curl "http://localhost:3210/api/v1/can/0/search?hash=a3b2"

# All JPEG images from last 24 hours
curl "http://localhost:3210/api/v1/can/0/search?mime_type=image/jpeg&start_time=1773014400000"

# Assets tagged with BOTH "sensor" AND "temperature"
curl "http://localhost:3210/api/v1/can/0/search?tags=sensor,temperature"

# Everything from a specific agent
curl "http://localhost:3210/api/v1/can/0/search?application=PlannerAgent&user=agent_v2"

# Combine filters
curl "http://localhost:3210/api/v1/can/0/search?tags=report&application=WebUI&order=asc&limit=5"
```

---

### 8. Get Thumbnail

Generate a resized thumbnail for image assets. Non-image assets return a placeholder SVG.

```
GET /api/v1/can/0/asset/{hash}/thumb/{max_width}/{max_height}
```

**Path Parameters:**

| Param | Type | Description |
|-------|------|-------------|
| `hash` | String | Asset hash |
| `max_width` | Integer | Maximum width in pixels |
| `max_height` | Integer | Maximum height in pixels |

Aspect ratio is always preserved. The image fits within the `max_width x max_height` box.

**Response:**
- **Image assets:** JPEG bytes (`Content-Type: image/jpeg`). Cached in `.thumbs/` if enabled.
- **Non-image assets:** SVG placeholder icon (`Content-Type: image/svg+xml`).

**Example:**

```bash
# 200x200 thumbnail
curl -o thumb.jpg http://localhost:3210/api/v1/can/0/asset/a3b2.../thumb/200/200
```

---

## Configuration

`config.yaml` at the project root (or pass a custom path as the first CLI argument):

```yaml
storage_root: "/var/lib/can_data"       # Where files are stored
admin_token: "super_secret_rebuild"     # Bearer token for admin operations
enable_thumbnail_cache: true            # Cache thumbnails in .thumbs/
rebuild_error_threshold: 50             # Error tolerance before hard rebuild
verify_interval_hours: 12               # Hours between integrity scrubs
```

---

## Concepts

### Hash

Every asset gets a unique SHA-256 hash computed as `SHA256(timestamp_be_bytes + file_content)`. This hash is the primary identifier used in all API calls. Because the timestamp is mixed in, even identical file content produces different hashes at different times.

### Physical Filename

Files are stored as: `{timestamp}_{hash}_{tags}.{extension}`

For example: `1773014400123_a3b2c4d5e6f7_finance_Q4.pdf`

This naming allows offline integrity verification -- you can recompute the hash from the timestamp and file contents and compare it to the filename.

### Tags

Tags are comma-separated strings. On ingest and in search, pass them as a single string: `"finance,Q4,report"`. In metadata responses, they come back as an array: `["finance", "Q4", "report"]`.

When searching, tag matching uses AND logic: `?tags=finance,Q4` finds only assets that have **both** tags.

When patching, tags are **replaced** entirely (not merged).

### Integrity Verification

A background verifier runs automatically:
1. **On startup:** Scrubs all assets against their hashes.
2. **On file change:** Watches the storage directory for modifications.
3. **Periodically:** Every `verify_interval_hours`.

Corrupted assets are flagged (`is_corrupted: true`) and excluded from standard list/search results unless `include_corrupted=true` is passed. Retrieving a corrupted asset via GET returns a 500 error.

### OS File Attributes

Critical metadata is written to the host OS as file attributes for disaster recovery:
- **Linux/macOS:** Extended attributes (`xattr`) under the `user.can.*` namespace
- **Windows:** NTFS Alternate Data Streams (`:can.*`)

This means the SQLite database can be rebuilt from scratch by scanning the storage directory.