Final acceptance: Консольная утилита поиска и скачивания изображений для вызова ИИ-агентом (#18)
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Co-authored-by: AI Tester <ai-tester@git.p2prod.ru>
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# product-54354138-1
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# product-54354138-1 image toolkit
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agent-intake-source: platform/product-requests#1
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A plain native-process command-line tool for a calling AI agent. One invocation
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accepts a request, searches an approved free image source, verifies every
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candidate against its *downloaded bytes* and writes **exactly one
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machine-readable JSON document** to stdout. The process exit code mirrors the
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document's `status`, so success, "nothing matched", a broken request and an
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unusable source are distinguishable without parsing prose.
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There is no Docker, no container image and no packaging step: the tool is run
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directly as an executable process with the interpreter that is already present.
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## Contents
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- [Requirements](#requirements)
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- [Running the tool](#running-the-tool)
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- [Request parameters](#request-parameters)
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- [JSON request document](#json-request-document)
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- [JSON response document](#json-response-document)
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- [Status vocabulary and exit codes](#status-vocabulary-and-exit-codes)
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- [Image sources](#image-sources)
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- [Download and resize behaviour](#download-and-resize-behaviour)
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- [Tests and checks](#tests-and-checks)
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## Requirements
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- Python >= 3.11 (declared in `pyproject.toml`).
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- No runtime third-party dependencies: the HTTPS client, PNG/ICO container
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parsing, decoding, resampling and re-encoding all live in the standard
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library and in `tools/`.
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- No API keys, tokens or registration for any source (see
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[Image sources](#image-sources)).
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There is nothing to install to *use* the tool from a checkout. Installing the
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project (`pip install .`, `uv sync`, ...) only matters for the optional test
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tooling.
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## Running the tool
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The tool is always invoked as a module of the working tree:
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```console
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python -m tools.example --topic "red fox" --width 640 --height 480 --format png
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```
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A JSON request document can be passed instead:
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```console
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python -m tools.example examples/input.json
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```
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`--help` is the authoritative parameter list; the table below is a summary:
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```console
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python -m tools.example --help
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```
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Rules for the two invocation styles:
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- Either a request document **or** flags must be given. With neither, the run
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fails with `invalid_request` (exit code 2).
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- A request document cannot be combined with any flag; doing so is
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`invalid_request` (exit code 2).
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## Request parameters
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| Parameter | Kind | Meaning |
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| --- | --- | --- |
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| `REQUEST.json` | positional | Path to a JSON request document holding the same fields as the flags. It cannot be combined with any of the flags. |
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| `-t`, `--topic TEXT` | text | Search topic (required unless a request document is given). |
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| `--width PX` | positive integer | Target width in pixels; only images at least this wide are accepted. |
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| `--height PX` | positive integer | Target height in pixels; only images at least this tall are accepted. |
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| `-f`, `--format FMT` | `png` or `ico` | Image format; required. Any other value is `invalid_request`. |
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| `-s`, `--source ID` | source id | Image source id (default: `wikimedia_commons`); unknown ids are rejected with the list of available sources. |
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| `-c`, `--count N` | integer 1-50 | How many candidates to request (default: `10`). |
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| `--download` | flag | Download every matching image into the output directory. |
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| `-o`, `--output-dir DIR` | path | Caller-specified download directory; required with `--download`. |
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| `--resize` | flag | Downscale every downloaded image that is larger than the request in either dimension to exactly the requested width and height, re-encoded in the requested format; images are never scaled up. Without it the original bytes and dimensions are written. |
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| `--dry-run` | flag | Validate the request and emit the envelope without any network access. |
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`--width` and `--height` are a **minimum**, not an exact match: an image that
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is at least that large is usable because it can be downscaled, while a smaller
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image would have to be scaled up and is therefore rejected. `--resize` decides
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whether the *stored* file is downscaled; it never changes this filter.
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`--count` bounds how many matching images are reported. Because nothing a
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source reports about a hit is trusted, the tool inspects a bounded window of up
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to `count * 4` candidates (capped at 50) and stops as soon as `count` verified
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images have been found.
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Short flags: `-t`/`--topic`, `-f`/`--format`, `-s`/`--source`, `-c`/`--count`,
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`-o`/`--output-dir`, `-h`/`--help`. Every other parameter is long-form only.
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## JSON request document
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The document accepted as the positional argument (see `examples/input.json`)
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is a single JSON **object** using the same names as the flags, in
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`snake_case`:
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```json
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{
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"version": 1,
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"topic": "red fox in the snow",
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"width": 640,
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"height": 480,
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"format": "png",
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"source": "wikimedia_commons",
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"count": 5,
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"download": false,
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"output_dir": "downloads",
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"resize": false,
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"dry_run": true
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}
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```
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| Field | Type | Required | Notes |
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| --- | --- | --- | --- |
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| `topic` | string, non-empty | yes | Same as `--topic`. |
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| `width` | integer > 0 or `null` | no | Minimum width; omitted/`null` means unconstrained. |
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| `height` | integer > 0 or `null` | no | Minimum height; omitted/`null` means unconstrained. |
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| `format` | `"png"` or `"ico"` | yes | Same as `--format`. |
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| `source` | string | no | Defaults to `wikimedia_commons`. |
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| `count` | integer 1-50 | no | Defaults to `10`. |
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| `download` | boolean | no | Defaults to `false`. |
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| `output_dir` | string, non-empty | required when `download` is `true` | Download directory. |
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| `resize` | boolean | no | Defaults to `false`. |
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| `dry_run` | boolean | no | Defaults to `false`. |
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| `version` | integer | no | Optional document metadata; accepted and otherwise ignored. |
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Document rules that produce `invalid_request` (exit code 2):
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- the file cannot be read, is not valid JSON, or is not a JSON object;
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- an unknown field is present (`error.code = "request_field"`, with
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`details.unknown_fields` and `details.accepted_fields`);
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- a field has the wrong type, is empty, or is out of range;
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- `format` is outside `png|ico`;
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- `download` is `true` while `output_dir` is absent or empty.
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## JSON response document
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Every run - success or failure - prints exactly one JSON document (one line) to
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stdout, with this fixed set of top-level keys:
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```json
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{
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"status": "ok",
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"source": "wikimedia_commons",
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"request": {"topic": "red fox", "width": 640, "height": 480, "format": "png", "source": "wikimedia_commons", "count": 1, "download": false, "output_dir": null, "resize": false, "dry_run": false},
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"items": [
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{
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"source": "wikimedia_commons",
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"url": "https://upload.wikimedia.org/wikipedia/commons/.../Fox.png",
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"file_url": "https://upload.wikimedia.org/wikipedia/commons/.../Fox.png",
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"format": "png",
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"width": 1280,
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"height": 853,
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"size_bytes": 1489231,
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"title": "File:Fox.png",
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"page_url": "https://commons.wikimedia.org/wiki/File:Fox.png",
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"mime_type": "image/png"
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}
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],
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"error": null
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}
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```
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| Key | Type | Meaning |
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| --- | --- | --- |
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| `status` | string | One value of the fixed vocabulary below. |
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| `source` | string or `null` | Source id the request selected, when known. |
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| `request` | object or `null` | The validated request (every field, defaults filled in), `null` when the request could not be validated. |
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| `items` | array | Verified images (empty unless `status` is `ok` or `partial_download`). |
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| `error` | object or `null` | `{"code", "message", "details"}`; `details` is optional. |
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An item is only reported after its bytes were downloaded and parsed, so its
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`format`, `width` and `height` are the **actual** values read from the payload
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container, never what the source claimed. `url` and `file_url` are the same
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direct HTTPS location; `file_url` is kept as an alias. `title`, `page_url` and
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`mime_type` are present only when the source provides them. `size_bytes` is the
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number of stored/fetched bytes.
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With `download` enabled every item additionally carries a `download` record:
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```json
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{"ok": true, "path": "downloads/001-file-fox.png", "bytes": 1489231, "format": "png", "width": 1280, "height": 853}
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```
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With `resize` enabled the record also carries a `resize` fragment:
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`{"requested": {...}, "from": {...}, "to": {...}, "format": "png", "applied": true}`
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(`"applied": false, "reason": "already_fits"` when nothing had to change).
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A file whose stored bytes do not read back as the requested format at the
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expected size is deleted and reported as `{"ok": false, "target": "...",
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"error": {...}}` instead of being named as saved.
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## Status vocabulary and exit codes
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The status vocabulary is fixed and every branch reuses it; the exit code is
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derived from the status.
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| `status` | Exit code | Meaning |
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| --- | --- | --- |
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| `ok` | 0 | At least one image really is the requested format and at least the requested width and height (all downloads completed when requested). |
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| `dry_run` | 0 | The request was validated and echoed without contacting a source. |
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| `invalid_request` | 2 | The request itself is unusable: bad or missing flags, unreadable/invalid document, unknown field, unsupported format, unknown source, or `download` without `output_dir`. |
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| `no_format` | 3 | The source answered but offers nothing in the requested format for the topic. |
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| `no_size` | 4 | The source has images of the requested format, but all of them are smaller than requested. |
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| `access_error` | 5 | The source could not be searched, or not a single candidate could be downloaded; never reported as "no match". |
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| `partial_download` | 6 | A download run where some images were saved and some could not be (see below). |
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The distinction is intentional and stable:
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- `no_format` / `no_size` describe the *topic*, not an outage, so they are not
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errors of the source.
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- A candidate whose bytes turn out to be a different format (JPEG, SVG, TIFF,
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an HTML error page, ...) is a format rejection that feeds `no_format`, not an
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access error.
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- `access_error` means the source could not be used at all; its `error.code`
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comes from the typed error (`source_unreachable`, `source_http_error`,
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`source_invalid_response`, `source_host_not_allowed`, `candidate_unreadable`,
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`access_error`).
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- `invalid_request` always carries a machine-readable `error.code`
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(`request_invalid`, `request_document`, `request_field`,
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`request_format_unsupported`, `source_unknown`) plus `error.details`.
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## Image sources
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Two working free sources ship with the tool. Neither needs an API key, a token,
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registration or a personal account; both are queried anonymously over HTTPS
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with a stable identifying `User-Agent`.
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| Source id | Service | Approved hosts |
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| --- | --- | --- |
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| `wikimedia_commons` (default) | Wikimedia Commons | `commons.wikimedia.org`, `upload.wikimedia.org` |
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| `openverse` | Openverse | `api.openverse.org` |
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Only those hosts on `https`/port 443 are contacted; any other URL is refused
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with `source_host_not_allowed` rather than fetched. HTTP 429 and 5xx responses
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are retried a bounded number of times with capped exponential backoff and then
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reported as `access_error`; a failed or unknown source is never silently
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degraded into an empty result.
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An unknown `--source` value fails with `invalid_request` and lists the
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available ids:
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```json
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{"error": {"code": "source_unknown", "message": "unknown image source 'nope'; available sources: openverse, wikimedia_commons", "details": {"source_id": "nope", "available_sources": ["openverse", "wikimedia_commons"]}}}
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```
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### Adding another source
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The registry in `tools/sources.py` is the extension point:
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- Implement the `SourceAdapter` protocol: a non-empty `source_id` string and
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`search(topic, limit) -> list[SourceCandidate]`.
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- Build `SourceCandidate` values whose `file_url` is an approved HTTPS URL and
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whose `fetch_bytes()` returns the image bytes through `HTTPSClient`.
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- Register the adapter with `SourceRegistry.register(adapter)` (a duplicate id
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raises `DuplicateSourceError`; `unregister(source_id)` removes one) and wire
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it into `build_registry()` / `default_registry()`, which is what the CLI uses.
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`HTTPSClient(allowed_hosts=...)` and `validate_source_url()` extend the
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approved-host allowlist for a new provider.
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- The new id becomes selectable through `--source` / `"source"` immediately;
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`SourceRegistry.get()` raises `UnknownSourceError` listing all registered ids
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for anything else.
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## Download and resize behaviour
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Two product decisions are fixed and documented here:
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1. **`--download` without `--output-dir` is an invalid request.** There is no
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hidden default directory; a download run without a caller-supplied
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directory could only guess where files should go. Such a run fails with
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`status: "invalid_request"`, exit code 2, and
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`error.code: "request_field"`, `error.details.field: "output_dir"`.
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The same rule applies to a request document with `"download": true` and no
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`output_dir`.
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2. **Partial saves are reported as `partial_download`.** When a download run
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saves some images but fails to fetch or verify others, the status is
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`partial_download` (exit code 6) - never `ok`. The document still lists every
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successfully saved item, and `error.code: "download_incomplete"` carries
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`details.saved`, `details.failed`, `details.total`, `details.saved_paths`
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and `details.failures`. A run in which every image was saved is `ok`
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(exit code 0); a run in which nothing could be fetched at all is
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`access_error` (exit code 5).
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Files are written into `--output-dir` as `NNN-<slug>.<format>`, created with
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`mkdir -p` semantics. Without `--resize` the verified original bytes are
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stored unchanged. With `--resize` each stored image is downscaled to exactly
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the requested width and height (a dimension left open keeps its source value)
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and re-encoded in the requested container format; an image already at or below
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the requested size is written unchanged and the resize fragment reports
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`"applied": false`. `--resize` never enlarges an image. A search without
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`--download` never touches the filesystem.
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## Tests and checks
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The test suite entry point is `pytest` from the repository root:
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```console
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pytest
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```
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Other repository checks used by CI:
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```console
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python -m compileall tools tests
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python -m tools.example --help
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python -m tools.example examples/input.json
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```
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`examples/input.json` is a `--dry-run` request, so the smoke command validates
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the contract and prints the envelope without any network access.
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Running the tests may require the declared dev dependency (`pytest>=8.0`) to be
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installed, for example `pip install -e '.[dev]'` or `uv sync`. That install is
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only for development; the tool itself runs as a plain process with no Docker or
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container packaging at any stage.
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Reference in New Issue
Block a user