import pandas as pd
import argparse
import re
import os
import yaml
import numpy as np
import warnings
from pathlib import Path

from sklearn.pipeline import Pipeline
from sklearn.compose import ColumnTransformer
from sklearn.preprocessing import OneHotEncoder,KBinsDiscretizer
from skmultilearn.model_selection import iterative_train_test_split

def extract_index_from_filename(filename : str):
    """
    Extract the numeric index from the filename (after first underscore).

    Parameters:
        filename (str): Filename to extract index from.

    Returns:
        str: Extracted index or None if not found.
    """
    match = re.search(r'_(\d+)_', os.path.basename(filename))
    if match:
        return match.group(0).replace("_","") 
    else:
        raise NameError(f"Run file {filename} does not contain the necessary run index information")


def extract_ride_height_from_filename(filename:str):
    """
    Parses the filename to extract front and rear ride heights

    Parameters:
        filename (str): .case Filename

    Returns:
        list[int]: Extracted ride heights
    """
    if re.search(r'(\d+)_(\d+)',os.path.basename(filename)):
        rh = (os.path.basename(filename).split("_")[2][:2]) + (os.path.basename(filename).split("_")[2][2:4])
    else:
        raise NameError(f"Run file {filename} does not contain the necessary ride height information")
    return rh

def get_run_info(run_folder: str, prefix:str) -> list[str]:
        """
        Looks for .npz or .zarr or .vtp or .vtu files and returns a dictionary containing run information
        about the available files

        Parameters:
            run_folder (str): path to the folder containing the preprocessed run files

        Returns:
            available_labels (dict): dictionary containing information about the available run files
                Run # (list[str]): list of available run numbers
                Rh (list[list[int]]): list of available ride heights
        """
        # Find all run files
        patterns = [
            rf"^{re.escape(prefix)}(\d+)\.(?:npz|zarr|vtp|vtu)$",
            rf"^{re.escape(prefix)}(\d+)_(\d+)\.(?:npz|zarr|vtp|vtu)$"
        ]
        pattern = re.compile("(" + ")|(".join(patterns) + ")")
        run_files = [str(f) for f in Path(run_folder).rglob('*') if f.is_file() and re.match(pattern, f.name)]

        if len(run_files) == 0:
            raise ValueError("No valid files found. Exiting.")
        
        # Extract run ids and ride heighs
        run_ids = [extract_index_from_filename(r) for r in run_files]
        rhs = [extract_ride_height_from_filename(r) for r in run_files]

        # Combine the run info
        available_labels = [x + "_" + y for x,y in zip(run_ids,rhs)]

        return available_labels


def parse_cfd_db(csv_file:str,label_cols:list[str],available_labels:list[str])-> pd.DataFrame:
    """
    Reads the CFD result database and parses the necessary columns for train/val/test split
    
    Parameters:
        csv_file (str): path to the .csv file
        label_cols (list[str]): list of columns to extract for stratified splitting
        available_labels (list[str]): list of conjoined Run # and RH information for each available data file
    Returns:
        df (pandas.Dataframe): Dataframe containing only the necessary information for splitting the data
    """

    geometry_cols = ["P", "CA", "OA", "CS", "OS", "AF"]
    columns = list(dict.fromkeys(label_cols + geometry_cols))

    # Load csv reading only selected columns
    df = pd.read_csv(csv_file,sep=";",usecols=columns,dtype=str)

    # Create column joining necessary run information for database filtering 
    df["RH"] = df["FRH"] + df["RRH"]
    df["run_index"] = df["Run #"].str.replace("_","") + "_" + df["RH"]

    # Filter rows based on available vtk files
    df = df.loc[df["run_index"].isin(available_labels)]

    for column in geometry_cols:
        df[column] = pd.to_numeric(df[column], errors="coerce")

    df.reset_index(inplace=True,drop=True)

    return df

def add_rh_info(split: list[str], db: pd.DataFrame, rh: list[str] | None):
    """
        Recompiles the split list by adding ride height information back into the indexes
        Finds all runs matching the given run ids, and adds new elements corresponding to the available ride heights

        Parameters:
            split (list[str]): list of run prefixes without ride height information
            db (pd.DataFrame): database containing information about the available run files
            rh (list[str] | None): ride heights to include, or all available ride heights

        Returns:
            split (list[str]): list of run indexes with associated ride height information
    """
    run_prefixes = db["run_index"].str.split("_").str[0]
    matching_rows = db[run_prefixes.isin(split)]
    if rh:
        matching_rows = matching_rows[matching_rows["RH"].isin(rh)]
    return matching_rows["run_index"].to_list()


def split_by_drag(run_prefixes: list[str], db: pd.DataFrame, drag_rh: str, val_size: float,
                   test_size: float, random_state: int) -> tuple[list[str], list[str], list[str]]:
    """
    Splits run prefixes into train/validation/test using drag coefficient (SCxav) outliers
    measured at one ride height. Outliers (lowest/highest SCxav) fill half of validation and
    half of test; the remaining quota of every split is filled randomly.

    Parameters:
        run_prefixes (list[str]): unique run prefixes to split
        db (pd.DataFrame): database containing run_index, RH and SCxav columns
        drag_rh (str): ride height used to compare SCxav values
        val_size (float): fraction of run_prefixes assigned to validation
        test_size (float): fraction of run_prefixes assigned to test
        random_state (int): seed for the random allocation of non-outlier runs

    Returns:
        train, validation, test (list[str]): run prefixes assigned to each split
    """
    drag_rows = db[db["RH"] == drag_rh].copy()
    drag_rows["run_prefix"] = drag_rows["run_index"].str.split("_").str[0]
    drag_rows = drag_rows[drag_rows["run_prefix"].isin(run_prefixes)]
    if len(drag_rows) != len(run_prefixes):
        raise ValueError(
            f"Expected one {drag_rh} row per run prefix, found "
            f"{len(drag_rows)} rows for {len(run_prefixes)} run prefixes"
        )

    drag_rows["SCxav"] = pd.to_numeric(drag_rows["SCxav"], errors="coerce")
    if drag_rows["SCxav"].isna().any():
        raise ValueError(f"SCxav contains missing or non-numeric values at RH {drag_rh}")

    n = len(drag_rows)
    validation_count = round(n * val_size)
    test_count = round(n * test_size)
    outlier_count = round(n * (val_size + test_size) / 2)
    outlier_count -= outlier_count % 2

    ranked = drag_rows.sort_values("SCxav")
    outliers = pd.concat([ranked.head(outlier_count // 2), ranked.tail(outlier_count // 2)])
    median = drag_rows["SCxav"].median()
    outliers = outliers.assign(distance=(outliers["SCxav"] - median).abs()).sort_values("distance", ascending=False)
    outlier_prefixes = outliers["run_prefix"].to_numpy()
    remaining_prefixes = drag_rows.loc[~drag_rows["run_prefix"].isin(outlier_prefixes), "run_prefix"].to_numpy()

    rng = np.random.default_rng(random_state)
    rng.shuffle(remaining_prefixes)

    validation_outlier_count = validation_count // 2
    test_outlier_count = test_count // 2
    required_outliers = validation_outlier_count + test_outlier_count
    if required_outliers > len(outlier_prefixes):
        raise ValueError("Not enough drag outliers for 50% validation/test allocation")

    # Alternate outliers by extremity, test getting the biggest one first
    ordered_outliers = outlier_prefixes[:required_outliers]
    test = ordered_outliers[0::2].tolist()
    validation = ordered_outliers[1::2].tolist()

    remaining_pool = np.concatenate([remaining_prefixes, outlier_prefixes[required_outliers:]])
    rng.shuffle(remaining_pool)

    validation_fill_count = validation_count - len(validation)
    test_fill_count = test_count - len(test)
    validation.extend(remaining_pool[:validation_fill_count].tolist())
    test.extend(remaining_pool[validation_fill_count:validation_fill_count + test_fill_count].tolist())

    assigned = set(validation) | set(test)
    train = [prefix for prefix in drag_rows["run_prefix"] if prefix not in assigned]
    return train, validation, test


def filter_by_samples(db: pd.DataFrame, samples_csv: str, geometry_cols: list[str]) -> pd.DataFrame:
    """
    Keeps only the runs whose geometry parameters are present in the provided samples file.

    Parameters:
        db (pd.DataFrame): database with geometry parameter columns already extracted
        samples_csv (str): path to a csv listing the desired samples (one row per sample,
            columns ordered as geometry_cols, '#' lines are treated as comments)
        geometry_cols (list[str]): geometry parameter columns to match on

    Returns:
        db (pd.DataFrame): filtered database containing only the requested samples
    """
    samples = pd.read_csv(samples_csv, sep=",", comment="#", header=None, names=geometry_cols)
    samples = samples.astype(float).drop_duplicates()

    db = db.copy()
    db[geometry_cols] = db[geometry_cols].astype(float)

    db = db.merge(samples, on=geometry_cols, how="inner")
    db.reset_index(inplace=True, drop=True)

    if len(db) == 0:
        raise ValueError(f"No runs match the samples listed in {samples_csv}")

    return db

def parse_run_range(run_range_str: str) -> list[str]:
    """
    Parse a run range string into a list of run indices.

    Parameters:
        run_range_str (str): Run range in format 'start-end' (e.g., '100-200')
                            or comma-separated list (e.g., '100,150,200')

    Returns:
        list[str]: List of run indices as strings
    """
    if '-' in run_range_str and ',' not in run_range_str:
        # Handle range format: 'start-end'
        start, end = run_range_str.split('-')
        return [str(i) for i in range(int(start), int(end) + 1)]
    elif ',' in run_range_str:
        # Handle comma-separated list: '100,150,200'
        return [s.strip() for s in run_range_str.split(',')]
    else:
        # Single value
        return [run_range_str.strip()]

def write_split_to_yaml(yaml_dict,output_path):

    for key in yaml_dict.keys():
        yaml_dict[key] = [str(r) if not isinstance(r,str) else r for r in yaml_dict[key] ]

    with open(output_path, 'w') as f:
        yaml.safe_dump(yaml_dict, f, default_flow_style=False,sort_keys=False)

    print(f"YAML split written to {output_path}")

def main():
    # Define default columns to read from csv file
    geometry_cols = ["P","CA","OA","CS","OS","AF"]
    default_cols = ["Run #","FRH","RRH","Body geometry"] + geometry_cols

    parser = argparse.ArgumentParser(
        description="Produces a .yaml file with train/val/test split for the given run files using stratified splitting"
    )
    parser.add_argument("run_folder", help="Folder with e.g. 'run_<id>.npy' files")
    parser.add_argument("csv_file", help="Path to the cfd database")
    parser.add_argument("config_file", type=str, help="save path for the YAML file")
    parser.add_argument("--label_cols",nargs="+",default=default_cols,help="Columns from the cfd database to use for stratification")
    parser.add_argument("--prefix",default="run_",help="Prefix of the files to split. Defaults to 'run_'")
    parser.add_argument("--ignore_rh",action="store_true",help="Ignore ride height information when splitting data")
    parser.add_argument("--samples_csv",help="Optional csv listing the samples to keep (one row per sample, columns ordered P,CA,OA,CS,OS,AF). Only matching runs are split.")
    parser.add_argument("--rh",nargs='+', type=str,help="Ride heights to add to the splits. Ignored when --ignore_rh is not enabled.")
    parser.add_argument("--split_by_drag", action="store_true", help="Split unique geometries using SCxav drag-coefficient outliers instead of stratified sampling.")
    parser.add_argument("--drag_rh", default="3030", help="Ride height used to compare SCxav for --split_by_drag. Defaults to 3030.")
    parser.add_argument("--random_state", type=int, default=42, help="Random seed for --split_by_drag outlier allocation. Defaults to 42.")
    parser.add_argument("--test_run_range",type=str,help="Run index range to assign to test set. Format: 'start-end' (e.g., '100-200') or comma-separated list (e.g., '100,150,200')")

    args = parser.parse_args()

    if args.split_by_drag and args.test_run_range:
        parser.error("--split_by_drag cannot be combined with --test_run_range")

    # Find actually available files
    available_runs = get_run_info(args.run_folder,args.prefix)

    # Ensure necessary columns are parsed from the csv
    label_cols = args.label_cols + [col for col in default_cols if col not in args.label_cols]
    if args.split_by_drag and "SCxav" not in label_cols:
        label_cols.append("SCxav")

    # Parse database
    db = parse_cfd_db(args.csv_file,label_cols,available_runs)

    # Keep only the samples listed in the provided csv file
    if args.samples_csv:
        db = filter_by_samples(db, args.samples_csv, geometry_cols)

    # Copy database for data splitting
    df = db.copy(deep=True)

    # Unique geometries must stay together across splits when RH is ignored or comparing drag
    if args.ignore_rh or args.split_by_drag:
        df.drop_duplicates(subset="Body geometry",inplace=True)
        df["run_index"] = df["run_index"].apply(lambda x: x.split("_")[0])

    if args.split_by_drag:
        val_size = 0.1
        test_size = 0.1
        train, validation, test = split_by_drag(
            df["run_index"].to_list(), db, args.drag_rh, val_size, test_size, args.random_state
        )
    else:
        # Keep only columns necessary from splitting
        keep_cols = ["run_index"] + (["RH"] if not args.ignore_rh else []) + geometry_cols
        df = df[keep_cols]

        # Prepare data for splitting
        continuos_cols = [c for c in geometry_cols if c != "P"]

        with warnings.catch_warnings(record=True) as rw:
            bin_numeric = KBinsDiscretizer(n_bins=15,encode="ordinal",strategy='uniform')
            one_hot_encode = OneHotEncoder(handle_unknown="error",sparse_output=False,)
            col_trans1 = ColumnTransformer(transformers=[("bin_numeric",bin_numeric,continuos_cols)],remainder="passthrough",verbose_feature_names_out=False)
            col_trans2 = ColumnTransformer(transformers=[("one_hot_encode",one_hot_encode,[c for c in df.columns if c != "run_index"])],remainder="drop",verbose_feature_names_out=False)
            pp = Pipeline([("col_trans1",col_trans1),("col_trans2",col_trans2)])
            pp.set_output(transform="pandas")
            one_hot_labels : pd.DataFrame = pp.fit_transform(df) # type: ignore

        # Converting to numpy
        df_run_index = df["run_index"].to_numpy().reshape(-1,1)
        one_hot_labels = one_hot_labels.to_numpy() # type: ignore

        # Handle manual test set assignment if specified
        if args.test_run_range:
            # Parse the run range
            test_run_indices = parse_run_range(args.test_run_range)

            # Clean Run # by removing leading zeros and trailing underscores
            df_cleaned_run_numbers = db["Run #"].str.replace("_","").str.lstrip("0")

            # Create mask for test runs based on cleaned Run # column
            test_mask = np.isin(df_cleaned_run_numbers.to_numpy(), test_run_indices)

            # Split data based on mask
            test = df_run_index[test_mask]
            remaining_df = df_run_index[~test_mask]
            remaining_labels = one_hot_labels[~test_mask]

            if len(test) == 0:
                raise ValueError(f"No runs found in specified test range: {args.test_run_range}")

            # Setup split parameters for train/val only
            train_size = 0.8
            val_size = 0.1

            # Split remaining data into train and validation
            train,_,val,_ = iterative_train_test_split(remaining_df, remaining_labels, test_size=val_size/(train_size+val_size))

            # Flatten ndArrays
            train = train.flatten().tolist()
            validation = val.flatten().tolist()
            test = test.flatten().tolist()
        else:
            # Original splitting logic when no test range is specified
            # Setup split parameters
            train_size = 0.8
            val_size = 0.1
            test_size = (1-val_size-train_size)/(1-train_size)

            # Split data twice
            train,_,x_test_val,y_test_val = iterative_train_test_split(df_run_index,one_hot_labels,test_size=1-train_size)
            val,_,test,_ = iterative_train_test_split(x_test_val,y_test_val,test_size=test_size)

            # Flatten ndArrays
            train = train.flatten().tolist()
            validation = val.flatten().tolist()
            test = test.flatten().tolist()

    # Add ride height information back into the splits
    if args.ignore_rh or args.split_by_drag:
        train = add_rh_info(train,db,args.rh)
        validation = add_rh_info(validation,db,args.rh)
        test = add_rh_info(test,db,args.rh)

    # Print to yaml
    yaml_dict = {
        "train" : train,
        "validation" : validation,
        "test" : test,
    }

    total_entries = sum(len(split) for split in yaml_dict.values())
    entry_proportions = {
        key: 100 * len(split) / total_entries
        for key, split in yaml_dict.items()
    }
    if args.ignore_rh or args.split_by_drag:
        total_prefixes = len({run_id.split("_")[0] for split in yaml_dict.values() for run_id in split})
        prefix_proportions = {
            key: 100 * len({run_id.split("_")[0] for run_id in split}) / total_prefixes
            for key, split in yaml_dict.items()
        }
        print(
            "Split proportions: "
            f"train={prefix_proportions['train']:.1f}%/{entry_proportions['train']:.1f}% "
            f"validation={prefix_proportions['validation']:.1f}%/{entry_proportions['validation']:.1f}% "
            f"test={prefix_proportions['test']:.1f}%/{entry_proportions['test']:.1f}% "
            "(prefixes/entries)"
        )
    else:
        print(
            "Split proportions: "
            f"train={entry_proportions['train']:.1f}% "
            f"validation={entry_proportions['validation']:.1f}% "
            f"test={entry_proportions['test']:.1f}%"
        )

    write_split_to_yaml(yaml_dict, args.config_file)

if __name__ == "__main__":
    main()