use std::fs;
use std::path::PathBuf;

fn values(input: &str) -> std::collections::BTreeMap<String, String> {
    input
        .split(';')
        .filter_map(|item| item.split_once('='))
        .map(|(key, value)| (key.to_owned(), value.to_owned()))
        .collect()
}

fn evaluate(kind: &str, input: &str) -> &'static str {
    let values = values(input);
    match kind {
        "version" if matches!(input, "1" | "0" | "-1") => "valid",
        "version" => "invalid:unsupported_version",
        "page" => match values.get("limit").and_then(|value| value.parse::<i64>().ok()) {
            Some(limit) if (1..=100).contains(&limit) => "valid",
            _ => "invalid:invalid_limit",
        },
        "manifest" if ["provider_url", "vm_address", "password", "private_key"]
            .iter()
            .any(|key| values.contains_key(*key)) => "invalid:forbidden_field",
        "manifest"
            if values.get("version").map(String::as_str) == Some("1")
                && values.contains_key("gateway_id")
                && values.get("grant").map_or(false, |value| value.len() >= 43)
                && values.get("purpose").map(String::as_str) == Some("launch") => "valid",
        "manifest" => "invalid:invalid_manifest",
        "clipboard" if values.get("encoding").map(String::as_str) == Some("utf-8")
            && !values.contains_key("file") => "valid",
        "clipboard" => "invalid:unsupported_clipboard",
        "event" if values.get("version").map(String::as_str) != Some("1") => {
            "invalid:unsupported_version"
        }
        "event" if values.get("after").and_then(|value| value.parse::<i64>().ok()).is_some()
            && values.get("earliest").and_then(|value| value.parse::<i64>().ok()).is_some()
            && values["after"].parse::<i64>().unwrap() > 0
            && values["earliest"].parse::<i64>().unwrap() > 0
            && values["after"].parse::<i64>().unwrap() < values["earliest"].parse::<i64>().unwrap() - 1 => {
            "invalid:gap"
        }
        "event" if values.get("payload_bytes").and_then(|value| value.parse::<usize>().ok()).map_or(true, |size| size > 16384) => {
            "invalid:payload_limit"
        }
        "event" if values.get("sequence").and_then(|value| value.parse::<i64>().ok()).map_or(true, |sequence| sequence < 1)
            || !values.contains_key("correlation_id") => "invalid:required",
        "event" => "valid",
        "tunnel" if matches!(values.get("offered").map(String::as_str), Some("1") | Some("0") | Some("-1"))
            && values.get("feature").map(String::as_str) == Some("control.v1") => "valid",
        "tunnel" if values.get("feature").map(String::as_str) != Some("control.v1") => {
            "invalid:unsupported_feature"
        }
        "tunnel" => "invalid:unsupported_version",
        "datagram" => classify_datagram(values.get("hex").map(String::as_str).unwrap_or_default()),
        _ => "invalid:unknown_kind",
    }
}

fn decode_hex(input: &str) -> Option<Vec<u8>> {
    if input.len() % 2 != 0 {
        return None;
    }
    (0..input.len())
        .step_by(2)
        .map(|index| u8::from_str_radix(&input[index..index + 2], 16).ok())
        .collect()
}

fn classify_datagram(encoded: &str) -> &'static str {
    let raw = match decode_hex(encoded) {
        Some(raw) => raw,
        None => return "invalid:hex",
    };
    if raw.len() < 21 {
        return "invalid:truncated";
    }
    if raw[0..2] != *b"VD" {
        return "invalid:magic";
    }
    if raw[2] != 1 {
        return "invalid:unsupported_version";
    }
    let limit = match raw[3] {
        1 => 1024,
        2 => 2048,
        3 => 65515,
        _ => return "invalid:unknown_channel",
    };
    if raw[4] != 0 {
        return "invalid:flags";
    }
    if raw[18] == 0 || raw[17] >= raw[18] {
        return "invalid:fragment";
    }
    let payload_length = ((raw[19] as usize) << 8) | raw[20] as usize;
    if payload_length > limit {
        return "invalid:payload_limit";
    }
    if raw.len() != 21 + payload_length {
        return "invalid:length_mismatch";
    }
    if raw.len() > 65536 {
        return "invalid:frame_limit";
    }
    "valid"
}

fn normalized_digest(results: &[String]) -> String {
    let mut value: u64 = 14695981039346656037;
    for result in results {
        for byte in format!("{result}\n").bytes() {
            value ^= u64::from(byte);
            value = value.wrapping_mul(1099511628211);
        }
    }
    format!("{value:016x}")
}

fn fixture_hash() -> String {
    let text = fs::read_to_string("fixtures/manifest.json").expect("fixture manifest");
    text.split("\"corpus_sha256\": \"")
        .nth(1)
        .and_then(|value| value.split('"').next())
        .expect("fixture hash")
        .to_owned()
}

fn main() {
    let mut paths: Vec<PathBuf> = fs::read_dir("fixtures/conformance")
        .expect("fixture corpus")
        .map(|entry| entry.expect("fixture entry").path())
        .filter(|path| path.extension().and_then(|value| value.to_str()) == Some("tsv"))
        .collect();
    paths.sort();
    let mut results = Vec::new();
    for path in paths {
        let text = fs::read_to_string(path).expect("fixture file");
        let mut lines = text.lines();
        assert_eq!(lines.next(), Some("id\tversion\tkind\tinput\texpected"));
        for line in lines {
            let fields: Vec<&str> = line.split('\t').collect();
            assert_eq!(fields.len(), 5);
            let actual = evaluate(fields[2], fields[3]);
            assert_eq!(actual, fields[4], "{}", fields[0]);
            results.push(format!("{}\t{}", fields[0], actual));
        }
    }
    println!(
        "Rust conformance passed normalized={} fixtures={}",
        normalized_digest(&results),
        fixture_hash()
    );
}