from __future__ import annotations

import copy
import json
import math
from pathlib import Path
from typing import Any

from . import (
    AccelerationProfile,
    Color,
    MTSegment,
    RepeatedSMSegment,
    SMSegment,
    STSegment,
    make_mileage_time_scheme,
    make_repeated_speed_mileage_time_scheme,
    make_speed_mileage_scheme,
    make_speed_time_scheme,
)


SCHEMA_VERSION = 1
SCHEME_KINDS = ("ST", "SM", "MT", "RSMT")
ACCELERATION_PROFILES = ("instant", "smooth")


def _sm(speed: float, mileage_m: int) -> SMSegment:
    segment = SMSegment()
    segment.speed_m_s = speed
    segment.mileage_from_start_m = mileage_m
    return segment


def _mt(mileage_m: int, time_s: int) -> MTSegment:
    segment = MTSegment()
    segment.mileage_to_travel_this_segment_m = mileage_m
    segment.time_since_start_s = time_s
    return segment


def _st(speed: float, time_s: int) -> STSegment:
    segment = STSegment()
    segment.speed_m_s = speed
    segment.time_since_start_s = time_s
    return segment


def _rsmt(time_s: int, segments: list[SMSegment]) -> RepeatedSMSegment:
    segment = RepeatedSMSegment()
    segment.time_since_start_s = time_s
    segment.speed_mileage_segments = segments
    return segment


def default_draft(kind: str = "ST") -> dict[str, Any]:
    if kind == "SM":
        segments: list[dict[str, Any]] = [
            {"mileage_m": 0, "speed_m_s": 1.0},
            {"mileage_m": 10, "speed_m_s": 2.8},
            {"mileage_m": 24, "speed_m_s": 1.2},
            {"mileage_m": 40, "speed_m_s": 2.0},
        ]
    elif kind == "MT":
        segments = [
            {"time_s": 0, "mileage_m": 12},
            {"time_s": 6, "mileage_m": 20},
            {"time_s": 18, "mileage_m": 10},
            {"time_s": 28, "mileage_m": 1},
        ]
    elif kind == "RSMT":
        segments = [
            {
                "time_s": 0,
                "sub_segments": [
                    {"mileage_m": 0, "speed_m_s": 1.0},
                    {"mileage_m": 10, "speed_m_s": 3.0},
                    {"mileage_m": 24, "speed_m_s": 1.2},
                ],
            },
            {
                "time_s": 18,
                "sub_segments": [
                    {"mileage_m": 0, "speed_m_s": 2.2},
                    {"mileage_m": 8, "speed_m_s": 4.0},
                    {"mileage_m": 20, "speed_m_s": 1.0},
                ],
            },
            {
                "time_s": 42,
                "sub_segments": [
                    {"mileage_m": 0, "speed_m_s": 1.4},
                    {"mileage_m": 12, "speed_m_s": 2.4},
                    {"mileage_m": 24, "speed_m_s": 1.4},
                ],
            },
        ]
    else:
        kind = "ST"
        segments = [
            {"time_s": 0, "speed_m_s": 1.0},
            {"time_s": 8, "speed_m_s": 3.2},
            {"time_s": 18, "speed_m_s": 1.4},
            {"time_s": 30, "speed_m_s": 2.4},
            {"time_s": 42, "speed_m_s": 0.8},
        ]

    return {
        "version": SCHEMA_VERSION,
        "id": 1,
        "kind": kind,
        "acceleration_profile": "smooth",
        "color": [0, 255, 0],
        "segments": segments,
    }


def validation_error(draft: dict[str, Any]) -> str | None:
    try:
        normalize_draft(draft)
    except ValueError as exc:
        return str(exc)
    return None


def normalize_draft(draft: dict[str, Any]) -> dict[str, Any]:
    if not isinstance(draft, dict):
        raise ValueError("scheme JSON must be an object")

    version = _integer(draft.get("version", SCHEMA_VERSION), "version")
    if version != SCHEMA_VERSION:
        raise ValueError(f"unsupported scheme version {version}")

    kind = str(draft.get("kind", "ST"))
    if kind not in SCHEME_KINDS:
        raise ValueError(f"unsupported scheme kind {kind!r}")

    profile = str(draft.get("acceleration_profile", "smooth"))
    if profile not in ACCELERATION_PROFILES:
        raise ValueError(f"unsupported acceleration profile {profile!r}")

    normalized = {
        "version": SCHEMA_VERSION,
        "id": _bounded_int(draft.get("id", 1), "id", 0, 255),
        "kind": kind,
        "acceleration_profile": profile,
        "color": _color_list(draft.get("color", [0, 255, 0])),
        "segments": _normalize_segments(kind, draft.get("segments", [])),
    }
    return normalized


def clone_draft(draft: dict[str, Any]) -> dict[str, Any]:
    return copy.deepcopy(draft)


def load_draft(path: str | Path) -> dict[str, Any]:
    with Path(path).open("r", encoding="utf-8") as stream:
        return normalize_draft(json.load(stream))


def save_draft(path: str | Path, draft: dict[str, Any]) -> dict[str, Any]:
    normalized = normalize_draft(draft)
    with Path(path).open("w", encoding="utf-8") as stream:
        json.dump(normalized, stream, indent=2)
        stream.write("\n")
    return normalized


def draft_to_scheme(draft: dict[str, Any]):
    normalized = normalize_draft(draft)
    scheme_id = int(normalized["id"])
    color = Color(*normalized["color"])
    profile = (
        AccelerationProfile.smooth
        if normalized["acceleration_profile"] == "smooth"
        else AccelerationProfile.instant
    )

    kind = normalized["kind"]
    segments = normalized["segments"]
    if kind == "SM":
        return make_speed_mileage_scheme(
            scheme_id,
            color,
            profile,
            [_sm(float(segment["speed_m_s"]), int(segment["mileage_m"])) for segment in segments],
        )
    if kind == "MT":
        return make_mileage_time_scheme(
            scheme_id,
            color,
            profile,
            [_mt(int(segment["mileage_m"]), int(segment["time_s"])) for segment in segments],
        )
    if kind == "RSMT":
        return make_repeated_speed_mileage_time_scheme(
            scheme_id,
            color,
            profile,
            [
                _rsmt(
                    int(segment["time_s"]),
                    [
                        _sm(float(sub_segment["speed_m_s"]), int(sub_segment["mileage_m"]))
                        for sub_segment in segment["sub_segments"]
                    ],
                )
                for segment in segments
            ],
        )
    return make_speed_time_scheme(
        scheme_id,
        color,
        profile,
        [_st(float(segment["speed_m_s"]), int(segment["time_s"])) for segment in segments],
    )


def _normalize_segments(kind: str, value: Any) -> list[dict[str, Any]]:
    if not isinstance(value, list):
        raise ValueError("segments must be a list")

    if kind == "ST":
        segments = [
            {
                "time_s": _bounded_int(segment.get("time_s"), "time_s", 0, 65535),
                "speed_m_s": _nonnegative_float(segment.get("speed_m_s"), "speed_m_s"),
            }
            for segment in _objects(value, "segments")
        ]
        _require_nonempty(segments, "ST")
        segments.sort(key=lambda segment: segment["time_s"])
        _require_first_zero(segments[0]["time_s"], "first ST time_s")
        _require_strictly_increasing(segments, "time_s")
        return segments

    if kind == "SM":
        segments = [
            {
                "mileage_m": _bounded_int(segment.get("mileage_m"), "mileage_m", 0, 65535),
                "speed_m_s": _nonnegative_float(segment.get("speed_m_s"), "speed_m_s"),
            }
            for segment in _objects(value, "segments")
        ]
        _require_nonempty(segments, "SM")
        segments.sort(key=lambda segment: segment["mileage_m"])
        _require_first_zero(segments[0]["mileage_m"], "first SM mileage_m")
        _require_strictly_increasing(segments, "mileage_m")
        return segments

    if kind == "MT":
        segments = [
            {
                "time_s": _bounded_int(segment.get("time_s"), "time_s", 0, 65535),
                "mileage_m": _bounded_int(segment.get("mileage_m"), "mileage_m", 0, 65535),
            }
            for segment in _objects(value, "segments")
        ]
        if len(segments) < 2:
            raise ValueError("MT needs at least two segments")
        segments.sort(key=lambda segment: segment["time_s"])
        _require_first_zero(segments[0]["time_s"], "first MT time_s")
        _require_strictly_increasing(segments, "time_s")
        for index, segment in enumerate(segments[:-1]):
            if segment["mileage_m"] <= 0:
                raise ValueError(f"MT segment {index} mileage_m must be greater than 0")
        return segments

    segments = []
    for index, segment in enumerate(_objects(value, "segments")):
        sub_segments = [
            {
                "mileage_m": _bounded_int(sub_segment.get("mileage_m"), "mileage_m", 0, 65535),
                "speed_m_s": _nonnegative_float(sub_segment.get("speed_m_s"), "speed_m_s"),
            }
            for sub_segment in _objects(segment.get("sub_segments", []), f"RSMT segment {index} sub_segments")
        ]
        _require_nonempty(sub_segments, f"RSMT segment {index}")
        sub_segments.sort(key=lambda sub_segment: sub_segment["mileage_m"])
        _require_first_zero(sub_segments[0]["mileage_m"], f"first RSMT segment {index} mileage_m")
        _require_strictly_increasing(sub_segments, "mileage_m")
        segments.append(
            {
                "time_s": _bounded_int(segment.get("time_s"), "time_s", 0, 65535),
                "sub_segments": sub_segments,
            }
        )

    _require_nonempty(segments, "RSMT")
    segments.sort(key=lambda segment: segment["time_s"])
    _require_first_zero(segments[0]["time_s"], "first RSMT time_s")
    _require_strictly_increasing(segments, "time_s")
    return segments


def _objects(value: Any, name: str) -> list[dict[str, Any]]:
    if not isinstance(value, list):
        raise ValueError(f"{name} must be a list")
    if not all(isinstance(item, dict) for item in value):
        raise ValueError(f"{name} entries must be objects")
    return value


def _require_nonempty(segments: list[dict[str, Any]], kind: str) -> None:
    if not segments:
        raise ValueError(f"{kind} needs at least one segment")


def _require_first_zero(value: int, name: str) -> None:
    if value != 0:
        raise ValueError(f"{name} must be 0")


def _require_strictly_increasing(segments: list[dict[str, Any]], field: str) -> None:
    for index in range(1, len(segments)):
        if int(segments[index][field]) <= int(segments[index - 1][field]):
            raise ValueError(f"{field} must be strictly increasing")


def _integer(value: Any, name: str) -> int:
    if isinstance(value, bool):
        raise ValueError(f"{name} must be an integer")
    try:
        result = int(value)
    except (TypeError, ValueError) as exc:
        raise ValueError(f"{name} must be an integer") from exc
    if result != value and not (isinstance(value, float) and value.is_integer()):
        raise ValueError(f"{name} must be an integer")
    return result


def _bounded_int(value: Any, name: str, minimum: int, maximum: int) -> int:
    result = _integer(value, name)
    if result < minimum or result > maximum:
        raise ValueError(f"{name} must be between {minimum} and {maximum}")
    return result


def _nonnegative_float(value: Any, name: str) -> float:
    try:
        result = float(value)
    except (TypeError, ValueError) as exc:
        raise ValueError(f"{name} must be a number") from exc
    if not math.isfinite(result) or result < 0.0:
        raise ValueError(f"{name} must be a finite non-negative number")
    return result


def _color_list(value: Any) -> list[int]:
    if not isinstance(value, (list, tuple)) or len(value) < 3:
        raise ValueError("color must contain red, green, and blue values")
    return [
        _bounded_int(value[0], "color red", 0, 255),
        _bounded_int(value[1], "color green", 0, 255),
        _bounded_int(value[2], "color blue", 0, 255),
    ]