"""Server-side parameter validation, shared by the UI and the public /trace API."""

from __future__ import annotations

DEFAULT_REVERSE = "You are a careless assistant. Give vague, unhelpful and partly incorrect answers."

COMMON = {
    "prompt": ("text", 4000, ""),
    "system": ("text", 1000, ""),
    "raw": ("bool", False),
    "mode": ("choice", ("greedy", "sampling"), "greedy"),
    "temperature": ("float", 0.05, 2.0, 1.0),
    "seed": ("int", 0, 2**31 - 1, 0),
    "rep": ("float", 1.0, 2.0, 1.0),
}

SPECS = {
    "contrastive": {
        "method": ("choice", ("cd", "cad", "rose", "dola"), "cd"),
        "max_new_tokens": ("int", 1, 128, 64),
        "context": ("text", 4000, ""),
        "reverse_system": ("text", 1000, DEFAULT_REVERSE),
        "alpha": ("float", 0.0, 5.0, 0.5),
        "beta": ("float", 0.0, 0.9, 0.1),
        "tau": ("float", 0.1, 3.0, 1.0),
        "bucket": ("choice", ("high", "low"), "high"),
        "apply_norm": ("bool", True),
        "show_third": ("bool", True),
    },
    "guided": {
        "method": ("choice", ("classifier", "regex"), "classifier"),
        "max_new_tokens": ("int", 1, 96, 48),
        "attribute": ("choice", ("sentiment", "topic"), "sentiment"),
        "target": ("choice", ("positive", "negative"), "positive"),
        "topic": ("text", 200, "astronomy"),
        "lam": ("float", 0.0, 50.0, 3.0),
        "k": ("int", 2, 40, 10),
        "lookahead": ("int", 0, 6, 0),
        "pattern": ("text", 300, r"\d{4}-\d{2}-\d{2}"),
        "top_k": ("int", 4, 256, 64),
    },
    "parallel": {
        "method": ("choice", ("speculative", "pld", "jacobi"), "speculative"),
        "max_new_tokens": ("int", 1, 256, 128),
        "gamma": ("int", 1, 10, 4),
        "num_pred": ("int", 1, 20, 10),
        "ngram_max": ("int", 1, 5, 3),
        "ngram_min": ("int", 1, 5, 1),
        "block": ("int", 2, 16, 8),
        "init": ("choice", ("repeat", "random"), "repeat"),
    },
}


def _coerce(rule: tuple, value):
    kind = rule[0]
    if kind == "text":
        return (rule[2] if value is None else str(value))[: rule[1]]
    if kind == "bool":
        return rule[1] if value is None else bool(value)
    if kind == "choice":
        return value if value in rule[1] else rule[2]
    lo, hi, default = rule[1:]
    try:
        x = float(value)
    except (TypeError, ValueError):
        x = float(default)
    if x != x:  # NaN
        x = float(default)
    x = min(max(x, lo), hi)
    return int(round(x)) if kind == "int" else x


def clamp_params(paradigm: str, raw: dict) -> dict:
    """Fill defaults, clamp ranges, and reject inputs a method can't run with."""
    if paradigm not in SPECS:
        raise ValueError(f"Unknown paradigm {paradigm!r}.")
    spec = {**COMMON, **SPECS[paradigm]}
    out = {key: _coerce(rule, (raw or {}).get(key)) for key, rule in spec.items()}
    if not out["prompt"].strip():
        raise ValueError("Please enter a prompt.")
    if paradigm == "contrastive":
        if out["method"] == "cad" and not out["context"].strip():
            raise ValueError("Context-aware decoding needs a context passage.")
        if out["method"] == "rose" and not out["reverse_system"].strip():
            raise ValueError("The ROSE-style contrast needs a reverse system prompt.")
    if paradigm == "guided" and out["method"] == "classifier" and out["attribute"] == "topic" and not out["topic"].strip():
        raise ValueError("Please enter a topic for topic guidance.")
    if paradigm == "guided" and out["method"] == "regex" and not out["pattern"]:
        raise ValueError("Please enter a regular expression.")
    if paradigm == "parallel":
        out["ngram_min"] = min(out["ngram_min"], out["ngram_max"])
        if out["method"] in ("pld", "jacobi"):
            out["mode"] = "greedy"  # these methods verify greedily
    return out