Harden Ollama HTTP and JSON error handling

[LostOne1000]

Priority

High

Summary

sendDataToApi() assumes that every Ollama response contains valid outer JSON, a string-valued response field, and valid model-generated JSON.

Several normal failures can therefore raise unhandled Lua exceptions:

• Ollama is unavailable.
• Ollama returns an HTTP error.
• The selected model rejects image input.
• The outer API response is malformed.
• response_data.response is missing or has the wrong type.
• The model response is not valid JSON.
• Markdown cleanup encounters a nil value.

The current failure path also returns a string while callers assume the result is a table.

Relevant code

lightroom-llama.lrplugin/LrLlama.lua

local response_data = JSON:decode(response)
local rawResponse = response_data.response

rawResponse = string.gsub(rawResponse, ...)

local response_json = JSON:decode(rawResponse)
return response_json

Failure path:

return "Error: Failed to send data to the API."

Caller:

props.title = apiResponse.title
props.caption = apiResponse.caption

Expected behavior

Every Ollama or parsing failure should leave the dialog operational and provide a useful error message.

Implementation notes

Introduce a consistent result contract, for example:

{
    success = true,
    data = {
        title = "...",
        caption = "...",
        keywords = {}
    }
}

or:

{
    success = false,
    error = "Ollama returned invalid JSON."
}

Protect JSON operations with pcall() and validate each layer before continuing.

Validate:

1. HTTP response exists.
2. HTTP status indicates success.
3. Outer response decodes to a table.
4. response exists and is a string.
5. Model response decodes to a table.

Acceptance criteria

• Ollama connection failures do not raise an unhandled Lua exception.
• Invalid outer JSON produces a recoverable error.
• Missing response fields produce a recoverable error.
• Invalid model-generated JSON produces a recoverable error.
• The function never returns a string where the caller expects a response table.
• The dialog returns to a usable state after every failure.
• Error messages contain actionable information without exposing the image payload.