api/main.py

"""JuaKazi Correction API — HTTP routing only."""

import time

from fastapi import FastAPI
from fastapi.middleware.cors import CORSMiddleware

from .audit import log as log_audit
from .ml_rewriter import ml_rewrite
from .rules_engine import apply_rules_on_spans, build_reason
from .schemas import RewriteRequest, RewriteResponse

import sys
from pathlib import Path
sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
from eval.correction_evaluator import SemanticPreservationMetrics

SEMANTIC_THRESHOLD = 0.70

app = FastAPI(title="JuaKazi Correction Engine (hybrid)", version="0.3")
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_methods=["*"],
    allow_headers=["*"],
)
semantic_metrics = SemanticPreservationMetrics()


@app.post("/rewrite", response_model=RewriteResponse)
def rewrite(req: RewriteRequest):
    t0 = time.time()
    rewritten, edits, matched_rules, skipped = apply_rules_on_spans(
        req.text, req.lang, flags=req.flags or None
    )
    source = "rules"
    ml_info = None
    semantic_score = None

    if rewritten != req.text:
        score = semantic_metrics.calculate_composite_preservation_score(req.text, rewritten)
        semantic_score = score["composite_score"]
        if semantic_score < SEMANTIC_THRESHOLD:
            rewritten, edits, source, semantic_score = req.text, [], "preserved", 1.0

    if matched_rules == 0 and source != "preserved":
        ml_out = ml_rewrite(req.text, lang=req.lang, num_return_sequences=3)
        ml_score = semantic_metrics.calculate_composite_preservation_score(req.text, ml_out["best"])
        if ml_score["composite_score"] < SEMANTIC_THRESHOLD:
            rewritten, source, semantic_score = req.text, "preserved", 1.0
        else:
            rewritten = ml_out["best"]
            source = "ml"
            semantic_score = ml_score["composite_score"]
            ml_info = ml_out
            edits.append({"from": req.text, "to": rewritten, "severity": "ml_fallback", "tags": "", "reason": "ML rewrite"})

    latency_ms = int((time.time() - t0) * 1000)
    confidence = {"rules": 0.85, "ml": 0.60, "preserved": 0.95}.get(source, 0.85)
    needs_review = source == "ml" or len(edits) == 0
    reason = build_reason(source, edits, skipped)
    has_bias_detected = any(e.get("severity") == "replace" for e in edits)

    response = {
        "id": req.id,
        "original_text": req.text,
        "rewrite": rewritten,
        "edits": edits,
        "confidence": confidence,
        "needs_review": needs_review,
        "source": source,
        "reason": reason,
        "semantic_score": semantic_score,
        "skipped_context": skipped or None,
        "has_bias_detected": has_bias_detected,
    }

    log_audit({
        "request": req.dict(),
        "response": response,
        "model_info": ml_info or {"model": "rulepack-v0.3"},
        "latency_ms": latency_ms,
        "region_dialect": req.region_dialect or "unknown",
    })
    return response


@app.post("/rewrite/batch")
def rewrite_batch(items: list):
    return [rewrite(RewriteRequest(**it)) for it in items]