openapi: 3.1.0
info:
  title: OpenData Log API
  version: 1.0.0
  description: HTTP API for the OpenData Log service — an append-only, key-partitioned log.

servers:
  - url: http://localhost:3001
    description: Local development server

paths:
  /api/v1/log/append:
    post:
      operationId: append
      summary: Append records
      description: |
        Append one or more records to the log. Each record has a key (used for
        partitioning scans) and a value (arbitrary bytes, both base64-encoded in
        JSON).

        Set `awaitDurable` to `true` to block until the records are persisted to
        durable storage. When `false` (the default), the server acknowledges the
        write as soon as records are buffered in memory.
      requestBody:
        required: true
        content:
          application/json:
            schema:
              $ref: "#/components/schemas/AppendRequest"
            example:
              records:
                - key: "dGVzdC1rZXk="
                  value: "dGVzdC12YWx1ZQ=="
              awaitDurable: false
      responses:
        "200":
          description: Records appended successfully.
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/AppendResponse"
              example:
                status: success
                recordsAppended: 1
                startSequence: 42
        "400":
          description: Invalid input (malformed JSON or missing fields).
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/ErrorResponse"
        "500":
          description: Internal server error.
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/ErrorResponse"

  /api/v1/log/scan:
    get:
      operationId: scan
      summary: Scan entries
      description: |
        Scan log entries for a given key within an optional sequence range.

        Supports **long-polling**: set `follow=true` to hold the connection open
        until new data arrives or `timeout_ms` elapses (default 30 000 ms). This
        is useful for tailing a log stream in near-real-time.
      parameters:
        - name: key
          in: query
          required: true
          description: Key to scan (URL-encoded if it contains special characters).
          schema:
            type: string
        - name: start_seq
          in: query
          required: false
          description: Start sequence number (inclusive). Defaults to `0`.
          schema:
            type: integer
            format: uint64
            minimum: 0
        - name: end_seq
          in: query
          required: false
          description: End sequence number (exclusive). Defaults to `max uint64`.
          schema:
            type: integer
            format: uint64
            minimum: 0
        - name: limit
          in: query
          required: false
          description: Maximum number of entries to return.
          schema:
            type: integer
            minimum: 0
        - name: follow
          in: query
          required: false
          description: If `true`, long-poll until data is available or timeout.
          schema:
            type: boolean
        - name: timeout_ms
          in: query
          required: false
          description: Timeout in milliseconds for long-polling. Default `30000`.
          schema:
            type: integer
            format: uint64
            minimum: 0
      responses:
        "200":
          description: Scan results.
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/ScanResponse"
              example:
                status: success
                key: "dGVzdC1rZXk="
                values:
                  - sequence: 42
                    value: "dGVzdC12YWx1ZQ=="
        "400":
          description: Invalid input (e.g. missing `key` parameter).
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/ErrorResponse"
        "500":
          description: Internal server error.
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/ErrorResponse"

  /api/v1/log/keys:
    get:
      operationId: listKeys
      summary: List keys
      description: |
        List distinct keys present in the log within an optional segment range.
      parameters:
        - name: start_segment
          in: query
          required: false
          description: Start segment ID (inclusive). Defaults to `0`.
          schema:
            type: integer
            format: uint32
            minimum: 0
        - name: end_segment
          in: query
          required: false
          description: End segment ID (exclusive). Defaults to `max uint32`.
          schema:
            type: integer
            format: uint32
            minimum: 0
        - name: limit
          in: query
          required: false
          description: Maximum number of keys to return.
          schema:
            type: integer
            minimum: 0
      responses:
        "200":
          description: List of keys.
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/KeysResponse"
              example:
                status: success
                keys:
                  - key: "ZXZlbnRz"
                  - key: "b3JkZXJz"
        "500":
          description: Internal server error.
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/ErrorResponse"

  /api/v1/log/segments:
    get:
      operationId: listSegments
      summary: List segments
      description: |
        List log segments whose start sequence falls within the given range.
        Segments are the physical storage units of the log.
      parameters:
        - name: start_seq
          in: query
          required: false
          description: Start sequence number (inclusive). Defaults to `0`.
          schema:
            type: integer
            format: uint64
            minimum: 0
        - name: end_seq
          in: query
          required: false
          description: End sequence number (exclusive). Defaults to `max uint64`.
          schema:
            type: integer
            format: uint64
            minimum: 0
      responses:
        "200":
          description: List of segments.
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/SegmentsResponse"
              example:
                status: success
                segments:
                  - id: 0
                    startSeq: 0
                    startTimeMs: 1705766400000
        "500":
          description: Internal server error.
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/ErrorResponse"

  /api/v1/log/count:
    get:
      operationId: count
      summary: Count entries
      description: |
        Count the number of log entries for a given key within an optional
        sequence range.
      parameters:
        - name: key
          in: query
          required: true
          description: Key to count (URL-encoded if it contains special characters).
          schema:
            type: string
        - name: start_seq
          in: query
          required: false
          description: Start sequence number (inclusive). Defaults to `0`.
          schema:
            type: integer
            format: uint64
            minimum: 0
        - name: end_seq
          in: query
          required: false
          description: End sequence number (exclusive). Defaults to `max uint64`.
          schema:
            type: integer
            format: uint64
            minimum: 0
      responses:
        "200":
          description: Entry count.
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/CountResponse"
              example:
                status: success
                count: 1024
        "400":
          description: Invalid input (e.g. missing `key` parameter).
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/ErrorResponse"
        "500":
          description: Internal server error.
          content:
            application/json:
              schema:
                $ref: "#/components/schemas/ErrorResponse"

components:
  schemas:
    Key:
      type: object
      description: Wrapper around a byte-string key (base64-encoded in JSON).
      properties:
        key:
          type: string
          format: byte
          description: The key bytes, base64-encoded.
      required:
        - key

    Record:
      type: object
      description: A single log record containing a key and a value.
      properties:
        key:
          type: string
          format: byte
          description: Partition key, base64-encoded.
        value:
          type: string
          format: byte
          description: Record payload, base64-encoded.
      required:
        - key
        - value

    AppendRequest:
      type: object
      description: Request body for appending records to the log.
      properties:
        records:
          type: array
          items:
            $ref: "#/components/schemas/Record"
          description: One or more records to append.
        awaitDurable:
          type: boolean
          default: false
          description: Whether to wait for durable persistence before responding.
      required:
        - records

    AppendResponse:
      type: object
      description: Response after successfully appending records.
      properties:
        status:
          type: string
          example: success
        recordsAppended:
          type: integer
          format: int32
          description: Number of records written.
        startSequence:
          type: integer
          format: uint64
          description: Sequence number assigned to the first appended record.
      required:
        - status
        - recordsAppended
        - startSequence

    Value:
      type: object
      description: A single log entry returned by scan.
      properties:
        sequence:
          type: integer
          format: uint64
          description: Global sequence number of this entry.
        value:
          type: string
          format: byte
          description: Entry payload, base64-encoded.
      required:
        - sequence
        - value

    ScanResponse:
      type: object
      description: Response containing scanned log entries for a key.
      properties:
        status:
          type: string
          example: success
        key:
          type: string
          format: byte
          description: The key that was scanned, base64-encoded.
        values:
          type: array
          items:
            $ref: "#/components/schemas/Value"
          description: Matching log entries.
      required:
        - status
        - values

    Segment:
      type: object
      description: Metadata for a log segment (physical storage unit).
      properties:
        id:
          type: integer
          format: uint32
          description: Segment ID.
        startSeq:
          type: integer
          format: uint64
          description: First sequence number in this segment.
        startTimeMs:
          type: integer
          format: int64
          description: Wall-clock timestamp (ms since epoch) when the segment was created.
      required:
        - id
        - startSeq
        - startTimeMs

    SegmentsResponse:
      type: object
      description: Response listing log segments.
      properties:
        status:
          type: string
          example: success
        segments:
          type: array
          items:
            $ref: "#/components/schemas/Segment"
      required:
        - status
        - segments

    KeysResponse:
      type: object
      description: Response listing distinct keys in the log.
      properties:
        status:
          type: string
          example: success
        keys:
          type: array
          items:
            $ref: "#/components/schemas/Key"
      required:
        - status
        - keys

    CountResponse:
      type: object
      description: Response containing the count of entries for a key.
      properties:
        status:
          type: string
          example: success
        count:
          type: integer
          format: uint64
          description: Number of entries matching the query.
      required:
        - status
        - count

    ErrorResponse:
      type: object
      description: Error response returned for all error cases.
      properties:
        status:
          type: string
          example: error
        message:
          type: string
          description: Human-readable error message.
      required:
        - status
        - message