//! Runs every case of every file in `contracts/test-vectors/` (SPEC §14.5.5) against `kvitt-domain`.
//!
//! The directory is read at test time (path from `CARGO_MANIFEST_DIR`), so a new vector file is picked up without a
//! code change; a file for a function this crate does not know fails the test unless it is one of the Kotlin-only
//! functions (SPEC §14.5.4 analytics and the category suggestion).

use std::collections::BTreeMap;
use std::path::PathBuf;

use kvitt_domain::{
    AccountPosition, Allocation, BalanceExpense, BalanceSettlement, SplitSpec, compute_balances,
    compute_split, over_settled_accounts, propose_allocation, validate_settlement,
};
use serde::Deserialize;
use serde::de::DeserializeOwned;
use serde_json::{Value, json};

/// Functions that exist only in Kotlin (SPEC §14.5.4, the category suggestion); their files are parsed but not run here.
const KOTLIN_ONLY: &[&str] = &["spend_series", "resolve_range", "suggest_category"];
/// Every Rust function of SPEC §14.5.2; each must have a vector file.
const RUST_FUNCTIONS: &[&str] = &[
    "compute_split",
    "compute_balances",
    "propose_allocation",
    "validate_settlement",
    "over_settled_accounts",
];

#[derive(Deserialize)]
struct VectorFile {
    format: u32,
    function: String,
    cases: Vec<Case>,
}

#[derive(Deserialize)]
struct Case {
    name: String,
    input: Value,
    expected: Value,
}

#[derive(Deserialize)]
struct SplitInput {
    amount_ore: i64,
    payer_user_id: String,
    user_ids: Vec<String>,
    spec: SplitSpec,
}

#[derive(Deserialize)]
struct BalancesInput {
    user_ids: Vec<String>,
    account_ids: Vec<String>,
    expenses: Vec<BalanceExpense>,
    settlements: Vec<BalanceSettlement>,
}

#[derive(Deserialize)]
struct ProposalInput {
    amount_ore: i64,
    accounts: Vec<AccountPosition>,
}

#[derive(Deserialize)]
struct SettlementInput {
    amount_ore: i64,
    from_user_id: String,
    to_user_id: String,
    user_ids: Vec<String>,
    allocations: Vec<Allocation>,
}

#[derive(Deserialize)]
struct OverSettledInput {
    allocations: Vec<Allocation>,
    accounts: Vec<AccountPosition>,
}

fn vectors_dir() -> PathBuf {
    PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("../../../contracts/test-vectors")
}

fn input<T: DeserializeOwned>(file: &str, case: &Case) -> T {
    serde_json::from_value(case.input.clone())
        .unwrap_or_else(|e| panic!("{file} / {}: bad input: {e}", case.name))
}

fn outcome<T: serde::Serialize, E: serde::Serialize>(result: Result<T, E>) -> Value {
    match result {
        Ok(v) => json!({ "ok": v }),
        Err(e) => json!({ "error": e }),
    }
}

fn run(function: &str, file: &str, case: &Case) -> Value {
    match function {
        "compute_split" => {
            let i: SplitInput = input(file, case);
            outcome(compute_split(
                i.amount_ore,
                &i.payer_user_id,
                &i.user_ids,
                &i.spec,
            ))
        }
        "compute_balances" => {
            let i: BalancesInput = input(file, case);
            let b = compute_balances(&i.user_ids, &i.account_ids, &i.expenses, &i.settlements);
            json!({ "ok": b })
        }
        "propose_allocation" => {
            let i: ProposalInput = input(file, case);
            outcome(propose_allocation(i.amount_ore, &i.accounts))
        }
        "validate_settlement" => {
            let i: SettlementInput = input(file, case);
            outcome(validate_settlement(
                i.amount_ore,
                &i.from_user_id,
                &i.to_user_id,
                &i.user_ids,
                &i.allocations,
            ))
        }
        "over_settled_accounts" => {
            let i: OverSettledInput = input(file, case);
            json!({ "ok": over_settled_accounts(&i.allocations, &i.accounts) })
        }
        other => panic!("{file}: no Rust implementation for function {other}"),
    }
}

#[test]
fn every_vector_file_passes() {
    let dir = vectors_dir();
    let mut entries: Vec<PathBuf> = std::fs::read_dir(&dir)
        .unwrap_or_else(|e| panic!("cannot read {}: {e}", dir.display()))
        .map(|entry| entry.expect("directory entry").path())
        .filter(|p| p.extension().is_some_and(|x| x == "json"))
        .collect();
    entries.sort();
    assert!(!entries.is_empty(), "no vector files in {}", dir.display());

    let mut seen: BTreeMap<String, usize> = BTreeMap::new();
    let mut failures: Vec<String> = Vec::new();
    for path in &entries {
        let file = path
            .file_name()
            .map(|n| n.to_string_lossy().into_owned())
            .unwrap_or_default();
        let text = std::fs::read_to_string(path).expect("read vector file");
        let vectors: VectorFile = serde_json::from_str(&text)
            .unwrap_or_else(|e| panic!("{file}: not a vector file (SPEC §14.5.5): {e}"));
        assert_eq!(vectors.format, 1, "{file}: unknown format");
        assert_eq!(
            file,
            format!("{}.json", vectors.function),
            "{file}: file name must be <function>.json"
        );
        assert!(!vectors.cases.is_empty(), "{file}: no cases");
        if KOTLIN_ONLY.contains(&vectors.function.as_str()) {
            seen.insert(vectors.function.clone(), 0);
            continue;
        }
        for case in &vectors.cases {
            let actual = run(&vectors.function, &file, case);
            if actual != case.expected {
                failures.push(format!(
                    "{file} / {}: expected {}, got {}",
                    case.name, case.expected, actual
                ));
            }
        }
        seen.insert(vectors.function.clone(), vectors.cases.len());
    }

    for function in RUST_FUNCTIONS {
        assert!(
            seen.get(*function).is_some_and(|n| *n > 0),
            "no vector cases for {function}"
        );
    }
    for (function, cases) in &seen {
        println!("{function}: {cases} cases run");
    }
    assert!(
        failures.is_empty(),
        "{} failing cases:\n{}",
        failures.len(),
        failures.join("\n")
    );
}