//! Generate difficulty-stratified seed catalogs for `EASY_SEEDS`, `MEDIUM_SEEDS`,
//! `HARD_SEEDS`, `EXPERT_SEEDS`, and `GRANDMASTER_SEEDS` in
//! `solitaire_data/src/difficulty_seeds.rs`.
//!
//! A seed's tier is determined by the **smallest** `SolverConfig` budget that
//! returns `SolverResult::Winnable`. Seeds that are `Unwinnable` at any budget
//! are discarded; `Inconclusive` at all budgets are also discarded (we only emit
//! provably-winnable seeds).
//!
//! # Usage
//!
//! ```bash
//! cargo run -p solitaire_assetgen --bin gen_difficulty_seeds --release -- \
//!     --start 0xD1FF0000_00000000 --per-tier 40
//! ```
//!
//! Flags:
//!   --start     Starting seed (decimal or 0x-prefixed hex, default 0xD1FF000000000000)
//!   --per-tier  Seeds to emit per tier (default 40)
//!   --help      Print this message

use solitaire_core::game_state::DrawMode;
use solitaire_core::solver::{try_solve, SolverConfig, SolverResult};

// Budget boundaries defining each tier. A seed belongs to the lowest tier
// whose budget proves it Winnable.
const BUDGETS: &[(&str, u64, usize)] = &[
    ("Easy",        1_000,   1_000),
    ("Medium",      5_000,   5_000),
    ("Hard",       25_000,  25_000),
    ("Expert",    100_000, 100_000),
    ("Grandmaster", 200_000, 200_000),
];

fn main() {
    let mut args = std::env::args().skip(1).peekable();
    let mut start: u64 = 0xD1FF_0000_0000_0000;
    let mut per_tier: usize = 40;

    while let Some(arg) = args.next() {
        match arg.as_str() {
            "--start" => {
                let val = args.next().unwrap_or_else(|| {
                    eprintln!("error: --start requires a value");
                    std::process::exit(1);
                });
                start = parse_u64(&val);
            }
            "--per-tier" => {
                let val = args.next().unwrap_or_else(|| {
                    eprintln!("error: --per-tier requires a value");
                    std::process::exit(1);
                });
                per_tier = val.parse().unwrap_or_else(|_| {
                    eprintln!("error: --per-tier must be a positive integer");
                    std::process::exit(1);
                });
            }
            "--help" | "-h" => {
                eprintln!("gen_difficulty_seeds: generate tiered seed catalogs");
                eprintln!("  --start <seed>     starting seed (hex or decimal)");
                eprintln!("  --per-tier <n>     seeds per tier (default 40)");
                return;
            }
            other => {
                eprintln!("error: unknown argument: {other}");
                std::process::exit(1);
            }
        }
    }

    if per_tier == 0 {
        eprintln!("error: --per-tier must be > 0");
        std::process::exit(1);
    }

    let draw_mode = DrawMode::DrawOne;
    let num_tiers = BUDGETS.len();
    let mut buckets: Vec<Vec<u64>> = vec![Vec::with_capacity(per_tier); num_tiers];
    let mut tried: u64 = 0;
    let mut seed = start;

    eprintln!(
        "gen_difficulty_seeds: finding {} seeds per tier from 0x{start:016X} (DrawOne) …",
        per_tier
    );
    eprintln!(
        "  Tiers: {}",
        BUDGETS.iter().map(|(n, _, _)| *n).collect::<Vec<_>>().join(", ")
    );

    while buckets.iter().any(|b| b.len() < per_tier) {
        tried += 1;
        'tier: for (i, &(name, move_budget, state_budget)) in BUDGETS.iter().enumerate() {
            if buckets[i].len() >= per_tier {
                continue;
            }
            let cfg = SolverConfig { move_budget, state_budget };
            match try_solve(seed, draw_mode, &cfg) {
                SolverResult::Winnable => {
                    buckets[i].push(seed);
                    eprintln!(
                        "  [{name}  {:>3}/{}]  0x{seed:016X}  (tried {tried})",
                        buckets[i].len(),
                        per_tier
                    );
                    break 'tier; // assign to the cheapest tier that proves it winnable
                }
                SolverResult::Unwinnable => {
                    // Definitely unsolvable — skip all remaining tiers.
                    break 'tier;
                }
                SolverResult::Inconclusive => {
                    // Budget exhausted without proof — try the next larger tier.
                    // If this is the last tier, the seed is discarded (Inconclusive
                    // at max budget means "probably but not provably winnable").
                    if i == num_tiers - 1 {
                        break 'tier;
                    }
                }
            }
        }
        seed = seed.wrapping_add(1);
    }

    eprintln!("\nDone ({tried} seeds examined). Paste the blocks below into difficulty_seeds.rs:\n");

    let date = current_date();
    for (i, (tier_name, _, _)) in BUDGETS.iter().enumerate() {
        println!(
            "    // Generated by solitaire_assetgen::gen_difficulty_seeds \
             (tier={tier_name}, date={date})"
        );
        for chunk in buckets[i].chunks(5) {
            for s in chunk {
                println!(
                    "    0x{:04X}_{:04X}_{:04X}_{:04X},",
                    (s >> 48) & 0xFFFF,
                    (s >> 32) & 0xFFFF,
                    (s >> 16) & 0xFFFF,
                    s & 0xFFFF,
                );
            }
        }
        println!();
    }
}

fn parse_u64(s: &str) -> u64 {
    let cleaned = s.replace('_', "");
    if let Some(hex) = cleaned.strip_prefix("0x").or_else(|| cleaned.strip_prefix("0X")) {
        u64::from_str_radix(hex, 16).unwrap_or_else(|_| {
            eprintln!("error: could not parse '{s}' as a hex u64");
            std::process::exit(1);
        })
    } else {
        cleaned.parse().unwrap_or_else(|_| {
            eprintln!("error: could not parse '{s}' as a decimal u64");
            std::process::exit(1);
        })
    }
}

fn current_date() -> String {
    use std::time::{SystemTime, UNIX_EPOCH};
    let secs = SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .map(|d| d.as_secs())
        .unwrap_or(0);
    let days = secs / 86400;
    let mut y = 1970u64;
    let mut d = days;
    loop {
        let leap = (y.is_multiple_of(4) && !y.is_multiple_of(100)) || y.is_multiple_of(400);
        let days_in_year = if leap { 366 } else { 365 };
        if d < days_in_year {
            break;
        }
        d -= days_in_year;
        y += 1;
    }
    let leap = (y.is_multiple_of(4) && !y.is_multiple_of(100)) || y.is_multiple_of(400);
    let month_days: [u64; 12] = [
        31, if leap { 29 } else { 28 }, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31,
    ];
    let mut m = 0usize;
    for &md in &month_days {
        if d < md {
            break;
        }
        d -= md;
        m += 1;
    }
    format!("{y}-{:02}-{:02}", m + 1, d + 1)
}