"""
result.py — GET /result/{job_id}

Returns the full step history for a job plus backward-compatible top-level
status/image URL fields derived from the current step.

Response design
---------------
The response includes two layers:

1. Top-level fields (backward-compatible with the current frontend polling):
     status             — current step's status
     result_image_url   — current step's result image URL
     original_image_url — step 0's original image URL (the uploaded file)
     error_message      — current step's error (if failed)

2. steps[] array (for the future multi-step navigation UI):
     Each entry has step_number, status, original_image_url, result_image_url,
     error_message.  The frontend (next step) uses this to render a step
     navigator.

URL derivation
--------------
Files live under STORAGE_DIR and are served at /storage/... by StaticFiles.
Path.relative_to(STORAGE_DIR).as_posix() extracts the relative path and
normalises Windows backslashes to forward slashes.
"""

from pathlib import Path

from fastapi import APIRouter, HTTPException

from app.config import STORAGE_DIR
from app.jobs_store import get_job

router = APIRouter()


def _to_url(abs_path: str | None) -> str | None:
    """Convert an absolute path under STORAGE_DIR to a /storage/… URL."""
    if abs_path is None:
        return None
    try:
        rel = Path(abs_path).relative_to(STORAGE_DIR)
        return "/storage/" + rel.as_posix()
    except ValueError:
        return None


@router.get("/{job_id}")
def get_result(job_id: str) -> dict:
    """Return current job state including full step history.

    The top-level status/result_image_url/original_image_url fields reflect
    the current step, keeping existing frontend polling code working until
    the multi-step UI is implemented.
    """
    job = get_job(job_id)
    if job is None:
        raise HTTPException(status_code=404, detail=f"Job '{job_id}' not found.")

    # Find current step record.
    current = next(
        (s for s in job.steps if s.step_number == job.current_step), None
    )

    # Step 0's original is the canonical "uploaded image" for before/after.
    step0 = next((s for s in job.steps if s.step_number == 0), None)

    # Build per-step summary for the history navigator.
    steps_summary = [
        {
            "step_number":       s.step_number,
            "status":            s.status,
            "original_image_url": _to_url(s.original_image),
            "result_image_url":   _to_url(s.result_image),
            "error_message":      s.error_message,
        }
        for s in sorted(job.steps, key=lambda s: s.step_number)
    ]

    return {
        # Backward-compatible top-level fields (polled by existing frontend).
        "job_id":             job.id,
        "current_step":       job.current_step,
        "status":             current.status            if current else "unknown",
        "error_message":      current.error_message     if current else None,
        "original_image_url": _to_url(step0.original_image) if step0 else None,
        "result_image_url":   _to_url(current.result_image) if current else None,
        # Full history for the multi-step UI (used in the next frontend step).
        "steps":              steps_summary,
    }