Extract text, tables, and form key-value pairs from a single-page document with Amazon Textract AnalyzeDocument and reassemble the Block graph into structured output

Documented steps

1. Grant IAM permission textract:AnalyzeDocument to the caller, plus s3:GetObject if the input is passed as an S3Object rather than inline Bytes.
2. Call AnalyzeDocument with Document={Bytes|S3Object} and FeatureTypes=["TABLES","FORMS"]. Reference: https://docs.aws.amazon.com/textract/latest/dg/API_AnalyzeDocument.html
3. Confirm the input is a single page in JPEG/PNG/PDF/TIFF and under 10 MB — synchronous operations accept one page and 10 MB maximum (limits-document.html).
4. Parse the response Blocks array and build an Id->Block map first, so Relationships (arrays of {Type, Ids}) can be resolved by lookup instead of repeated scans.
5. For plain text: walk PAGE -> Relationships[Type=CHILD] -> LINE -> Relationships[Type=CHILD] -> WORD, concatenating each WORD's Text field.
6. For tables: for each TABLE block follow Relationships[Type=CHILD] to CELL ids; read each CELL's 1-based RowIndex/ColumnIndex, then follow that CELL's own Relationships[Type=CHILD] to WORD/SELECTION_ELEMENT blocks for the cell text. Handle TABLE-level Relationships[Type=MERGED_CELL] separately.
7. For forms: for each KEY_VALUE_SET block with EntityTypes=["KEY"], follow Relationships[Type=VALUE] to the paired VALUE block, then read Relationships[Type=CHILD] on both KEY and VALUE to reach the WORD blocks holding the actual text.
8. Attach each block's Confidence (0-100 float) to the corresponding output field so downstream logic can flag low-confidence extractions for review.
9. Assemble a normalized result object such as {lines:[], tables:[[...]], forms:{key:value}} from the traversed blocks.