add /solver endpoint for PoW solver script download

app/api/routes.py

@@ -469,6 +469,7 @@ class IndexView(MethodView):
                     f"GET {prefixed_url('/')}": "API information",
                     f"GET {prefixed_url('/health')}": "Health check",
                     f"GET {prefixed_url('/client')}": "Download CLI client",
+                    f"GET {prefixed_url('/solver')}": "Download PoW solver script",
                     f"GET {prefixed_url('/challenge')}": "Get PoW challenge",
                     f"POST {prefixed_url('/')}": "Create paste",
                     f"GET {prefixed_url('/pastes')}": "List your pastes (auth required)",
@@ -756,6 +757,91 @@ class ClientView(MethodView):
             return error_response("Client not available", 404)
 
 
+class SolverView(MethodView):
+    """PoW solver script download endpoint."""
+
+    def get(self) -> Response:
+        """Serve a Python script for solving PoW challenges."""
+        server_url = base_url()
+        script = f'''#!/usr/bin/env python3
+"""FlaskPaste PoW solver - solves challenges for curl-based uploads."""
+import hashlib
+import json
+import sys
+import urllib.request
+
+SERVER = "{server_url}"
+
+
+def get_challenge():
+    """Fetch a new challenge from the server."""
+    with urllib.request.urlopen(f"{{SERVER}}/challenge") as r:
+        return json.load(r)
+
+
+def solve(nonce: str, difficulty: int) -> int:
+    """Find solution where sha256(nonce:solution) has sufficient leading zero bits."""
+    i = 0
+    while True:
+        h = hashlib.sha256(f"{{nonce}}:{{i}}".encode()).digest()
+        zero_bits = 0
+        for byte in h:
+            if byte == 0:
+                zero_bits += 8
+            else:
+                zero_bits += 8 - byte.bit_length()
+                break
+        if zero_bits >= difficulty:
+            return i
+        i += 1
+
+
+def main():
+    if len(sys.argv) < 2:
+        print("Usage: fpaste-solver <file>", file=sys.stderr)
+        print("       cat data | fpaste-solver -", file=sys.stderr)
+        sys.exit(1)
+
+    # Read content
+    if sys.argv[1] == "-":
+        content = sys.stdin.buffer.read()
+    else:
+        with open(sys.argv[1], "rb") as f:
+            content = f.read()
+
+    # Get and solve challenge
+    ch = get_challenge()
+    if not ch.get("enabled", True):
+        token, solution = "", ""
+    else:
+        print(f"Solving PoW (difficulty={{ch['difficulty']}})...", file=sys.stderr)
+        solution = solve(ch["nonce"], ch["difficulty"])
+        token = ch["token"]
+        print(f"Solved: {{solution}}", file=sys.stderr)
+
+    # Upload
+    req = urllib.request.Request(
+        f"{{SERVER}}/",
+        data=content,
+        headers={{
+            "Content-Type": "application/octet-stream",
+            "X-PoW-Token": token,
+            "X-PoW-Solution": str(solution),
+        }},
+    )
+    with urllib.request.urlopen(req) as r:
+        result = json.load(r)
+        print(result.get("raw", result.get("url", json.dumps(result))))
+
+
+if __name__ == "__main__":
+    main()
+'''
+        response = Response(script, mimetype="text/x-python")
+        response.headers["Content-Disposition"] = "attachment; filename=fpaste-solver"
+        return response
+
+
 class PasteView(MethodView):
     """Paste metadata operations."""
 
@@ -1399,6 +1485,7 @@ bp.add_url_rule("/", view_func=IndexView.as_view("index"))
 bp.add_url_rule("/health", view_func=HealthView.as_view("health"))
 bp.add_url_rule("/challenge", view_func=ChallengeView.as_view("challenge"))
 bp.add_url_rule("/client", view_func=ClientView.as_view("client"))
+bp.add_url_rule("/solver", view_func=SolverView.as_view("solver"))
 
 # Paste operations
 bp.add_url_rule("/pastes", view_func=PastesListView.as_view("pastes_list"))