from __future__ import annotations

import math
import random
from typing import Any

from src import config
from src.config import GenerationParams
from src.errors import UserFacingError


def _as_int(name: str, value: Any, lo: int, hi: int) -> int:
    if value is None:
        raise UserFacingError(f"Missing value for {name!r}.")
    try:
        n = int(round(float(value)))
    except (TypeError, ValueError):
        raise UserFacingError(
            f"Invalid {name!r}: expected a number in [{lo}, {hi}].", details=str(value)
        )
    if n < lo or n > hi:
        raise UserFacingError(
            f"Invalid {name!r}: {n} is outside the allowed range [{lo}, {hi}]."
        )
    return n


def _as_float(name: str, value: Any, lo: float, hi: float) -> float:
    if value is None:
        raise UserFacingError(f"Missing value for {name!r}.")
    try:
        n = float(value)
    except (TypeError, ValueError):
        raise UserFacingError(
            f"Invalid {name!r}: expected a number in [{lo}, {hi}].", details=str(value)
        )
    if not math.isfinite(n):
        raise UserFacingError(f"Invalid {name!r}: must be a finite number.")
    if n < lo or n > hi:
        raise UserFacingError(
            f"Invalid {name!r}: {n} is outside the allowed range [{lo}, {hi}]."
        )
    return n


def _clamp_int(name: str, value: Any, lo: int, hi: int) -> tuple[int, str | None]:
    """Return clamped int and optional warning if clamped from out-of-range input."""
    try:
        n = int(round(float(value)))
    except (TypeError, ValueError):
        raise UserFacingError(
            f"Invalid {name!r}: expected a number; got {value!r}.", details=repr(value)
        )
    if n < lo:
        return lo, f"{name} was {n} (below minimum {lo}); using {lo}."
    if n > hi:
        return hi, f"{name} was {n} (above maximum {hi}); using {hi}."
    return n, None


def _clamp_float(
    name: str,
    value: Any,
    lo: float,
    hi: float,
    *,
    step: float | None = None,
    decimals: int | None = None,
) -> tuple[float, str | None]:
    try:
        n = float(value)
    except (TypeError, ValueError):
        raise UserFacingError(
            f"Invalid {name!r}: expected a number; got {value!r}.", details=repr(value)
        )
    if not math.isfinite(n):
        raise UserFacingError(f"Invalid {name!r}: must be a finite number.")
    warn = None
    if n < lo:
        warn = f"{name} was {n} (below minimum {lo}); using {lo}."
        n = lo
    elif n > hi:
        warn = f"{name} was {n} (above maximum {hi}); using {hi}."
        n = hi
    if step is not None and step > 0:
        # Snap to grid relative to lo
        n = lo + round((n - lo) / step) * step
        n = min(hi, max(lo, n))
    if decimals is not None:
        n = round(n, decimals)
    return n, warn


def _normalize_sampler(name: str) -> tuple[str, str | None]:
    s = (name or "").strip()
    if not s:
        return config.DEFAULT_SAMPLER, f"Empty sampler: using default {config.DEFAULT_SAMPLER!r}."
    if s in config.SAMPLER_CHOICES:
        return s, None
    # Common alias from Z-Image / Z-Anime docs
    if s in ("euler_a", "euler-a", "euler a"):
        return "euler_ancestral", (
            f"Sampler {name!r} is not a known id; remapped to 'euler_ancestral'."
        )
    return config.DEFAULT_SAMPLER, (
        f"Sampler {name!r} is not in the supported set for this Space; using "
        f"{config.DEFAULT_SAMPLER!r}. Supported examples: {', '.join(config.SAMPLER_CHOICES[:6])}…"
    )


def _normalize_scheduler(name: str) -> tuple[str, str | None]:
    s = (name or "").strip()
    if not s:
        return config.DEFAULT_SCHEDULER, f"Empty scheduler: using default {config.DEFAULT_SCHEDULER!r}."
    if s in config.SCHEDULER_CHOICES:
        return s, None
    return config.DEFAULT_SCHEDULER, (
        f"Scheduler {name!r} is not in the supported set for this Space; using "
        f"{config.DEFAULT_SCHEDULER!r}."
    )


def validate_and_clamp(
    *,
    prompt: str,
    negative_prompt: str | None,
    width: Any,
    height: Any,
    steps: Any,
    cfg: Any,
    batch_size: Any,
    sampler_name: str | None,
    scheduler: str | None,
    denoise: Any,
    seed: Any = None,
    randomize_seed: bool = True,
) -> GenerationParams:
    """
    Validate and clamp all user parameters; collect non-fatal warnings.
    Rejects unparseable types with clear messages.
    """
    warnings: list[str] = []
    p = (prompt or "").strip()
    if not p:
        raise UserFacingError("Prompt must not be empty.")
    if len(p) > 20_000:
        raise UserFacingError("Prompt is too long (max 20,000 characters).")

    neg = (negative_prompt or "").strip()
    if len(neg) > 20_000:
        raise UserFacingError("Negative prompt is too long (max 20,000 characters).")

    w, wmsg = _clamp_int("width", width, config.MIN_WH, config.MAX_WH)
    if wmsg:
        warnings.append(wmsg)
    h, hmsg = _clamp_int("height", height, config.MIN_WH, config.MAX_WH)
    if hmsg:
        warnings.append(hmsg)
    st, stmsg = _clamp_int("steps", steps, config.MIN_STEPS, config.MAX_STEPS)
    if stmsg:
        warnings.append(stmsg)

    cfg_v, cmsg = _clamp_float("cfg", cfg, config.MIN_CFG, config.MAX_CFG, step=0.1, decimals=1)
    if cmsg:
        warnings.append(cmsg)
    d_v, dmsg = _clamp_float(
        "denoise", denoise, config.MIN_DENOISE, config.MAX_DENOISE, step=0.01, decimals=2
    )
    if dmsg:
        warnings.append(dmsg)

    bs, bmsg = _clamp_int("batch_size", batch_size, config.MIN_BATCH, config.MAX_BATCH)
    if bmsg:
        warnings.append(bmsg)

    sampler, sm = _normalize_sampler(sampler_name or "")
    if sm:
        warnings.append(sm)
    sched, sc = _normalize_scheduler(scheduler or "")
    if sc:
        warnings.append(sc)

    if randomize_seed:
        seed_value = random.randint(config.MIN_SEED, config.MAX_SEED)
    else:
        seed_value, seed_msg = _clamp_int("seed", seed, config.MIN_SEED, config.MAX_SEED)
        if seed_msg:
            warnings.append(seed_msg)

    return GenerationParams(
        prompt=p,
        negative_prompt=neg,
        width=w,
        height=h,
        steps=st,
        cfg=cfg_v,
        batch_size=bs,
        sampler_name=sampler,
        scheduler=sched,
        denoise=d_v,
        seed=seed_value,
        warnings=tuple(warnings),
    )