//! Pure text/history helpers for the client TUI.
//!
//! Nothing here touches the terminal, so it is unit-tested from `tests/`
//! without a PTY.

struct CommandHelp {
    name: &'static str,
    usage: &'static str,
    description: &'static str,
}

const COMMANDS: &[CommandHelp] = &[
    CommandHelp {
        name: "connect",
        usage: "connect <ip>:<port>",
        description: "connect to the server",
    },
    CommandHelp {
        name: "send",
        usage: "send <message>",
        description: "send a message to the server",
    },
    CommandHelp {
        name: "disconnect",
        usage: "disconnect",
        description: "disconnect from the server",
    },
    CommandHelp {
        name: "ping",
        usage: "ping",
        description: "ping the server",
    },
    CommandHelp {
        name: "login",
        usage: "login",
        description: "login to the server",
    },
    CommandHelp {
        name: "register",
        usage: "register",
        description: "register a new user",
    },
    CommandHelp {
        name: "setcred",
        usage: "setcred",
        description: "set credentials for the server's certificate key",
    },
    CommandHelp {
        name: "logout",
        usage: "logout",
        description: "logout from the server",
    },
    CommandHelp {
        name: "info",
        usage: "info",
        description: "show account and connection info",
    },
    CommandHelp {
        name: "play",
        usage: "play <game> [bet]",
        description: "start a game (e.g. play slots 50)",
    },
    CommandHelp {
        name: "games",
        usage: "games",
        description: "list available games",
    },
    CommandHelp {
        name: "help",
        usage: "help",
        description: "show this message",
    },
    CommandHelp {
        name: "forget-host",
        usage: "forget-host [ip:port]",
        description: "clear trust for one address (credentials stay while the key is in use)",
    },
    CommandHelp {
        name: "hosts",
        usage: "hosts",
        description: "list remembered hosts",
    },
    CommandHelp {
        name: "quit",
        usage: "quit",
        description: "quit the program",
    },
];

pub fn command_names() -> Vec<&'static str> {
    COMMANDS.iter().map(|command| command.name).collect()
}

pub fn help_lines() -> Vec<String> {
    let mut lines = vec!["Available commands:".to_string()];
    for command in COMMANDS {
        lines.push(format!("  {:<28} - {}", command.usage, command.description));
    }
    lines
}

/// Wrap a completion list to `width` columns, one space between names.
pub fn completion_lines(commands: &[&str], width: usize) -> Vec<String> {
    let mut lines = vec!["Possible completions:".to_string()];
    let mut current = String::new();

    for command in commands {
        let needed = if current.is_empty() {
            command.len()
        } else {
            current.len() + 1 + command.len()
        };
        if !current.is_empty() && needed > width {
            lines.push(current.clone());
            current.clear();
        }
        if !current.is_empty() {
            current.push(' ');
        }
        current.push_str(command);
    }

    if !current.is_empty() {
        lines.push(current);
    }
    lines
}

/// Add a command to the history, skipping blanks and consecutive duplicates.
pub fn record_history(history: &mut Vec<String>, line: &str) {
    let line = line.trim();
    if line.is_empty() {
        return;
    }
    if history.last().is_some_and(|last| last == line) {
        return;
    }
    history.push(line.to_string());
}

/// Parse the optional bet argument of `play <game> [bet]`.
pub fn parse_bet_arg(raw: &str) -> Result<u64, String> {
    let bet = raw
        .trim()
        .parse::<u64>()
        .map_err(|_| format!("Invalid bet: {raw}"))?;
    if bet < 10 {
        return Err("Bet must be at least 10 Kr".to_string());
    }
    Ok(bet)
}

/// Number of terminal columns used by `text`.
///
/// This is a deliberately small approximation of `unicode-width`: it handles
/// ASCII, Latin diacritics, combining marks, CJK, and the common emoji ranges
/// without adding a dependency.
pub fn display_width(text: &str) -> usize {
    let mut width = 0;
    let mut chars = text.chars().peekable();

    while let Some(character) = chars.next() {
        if character == '\x1b' {
            if chars.peek() == Some(&'[') {
                chars.next();
                // Skip CSI parameters until the final byte (@ through ~).
                for character in chars.by_ref() {
                    if ('@'..='~').contains(&character) {
                        break;
                    }
                }
            } else {
                // Two-character escape sequence.
                chars.next();
            }
            continue;
        }
        width += char_width(character);
    }

    width
}

fn char_width(c: char) -> usize {
    let cp = c as u32;
    if cp < 0x20 || cp == 0x7F {
        return 0;
    }
    if is_zero_width(cp) || is_combining(cp) {
        return 0;
    }
    if is_wide(cp) { 2 } else { 1 }
}

fn is_zero_width(cp: u32) -> bool {
    matches!(
        cp,
        0x200B..=0x200F | 0xFE00..=0xFE0F | 0xFEFF | 0x1F3FB..=0x1F3FF
    )
}

fn is_combining(cp: u32) -> bool {
    matches!(
        cp,
        0x0300..=0x036F
            | 0x1AB0..=0x1AFF
            | 0x1DC0..=0x1DFF
            | 0x20D0..=0x20FF
            | 0xFE20..=0xFE2F
    )
}

fn is_wide(cp: u32) -> bool {
    matches!(
        cp,
        0x1100..=0x115F
            | 0x2329..=0x232A
            | 0x2E80..=0xA4CF
            | 0xAC00..=0xD7A3
            | 0xF900..=0xFAFF
            | 0xFE10..=0xFE19
            | 0xFE30..=0xFE6F
            | 0xFF00..=0xFF60
            | 0xFFE0..=0xFFE6
            | 0x1F300..=0x1F64F
            | 0x1F680..=0x1F6FF
            | 0x1F900..=0x1F9FF
            | 0x20000..=0x3FFFD
    )
}

/// The three lines printed on first contact with a host.
pub fn first_contact_lines(addr: &str, fingerprint: &str) -> Vec<String> {
    vec![
        format!("First contact with {addr}: trusting a new certificate."),
        format!("Fingerprint: {fingerprint}"),
        "Future connections must present the same certificate key.".to_string(),
    ]
}

/// Format remembered hosts so a 64-character fingerprint does not wrap on an
/// 80-column terminal.
/// Smallest terminal every game fits in. Roulette's felt is 12 lines and the
/// controls are ~72 columns, so anything smaller would wrap or hide the board.
pub const MIN_COLUMNS: u16 = 80;
pub const MIN_ROWS: u16 = 24;

/// Refuse to start when the terminal cannot show every game.
pub fn terminal_too_small(columns: u16, rows: u16) -> Option<String> {
    if columns >= MIN_COLUMNS && rows >= MIN_ROWS {
        return None;
    }
    Some(format!(
        "zagan.bet needs a terminal of at least {MIN_COLUMNS}x{MIN_ROWS} cells, \
         but this one is {columns}x{rows}.\n\
         Resize it and start again."
    ))
}

/// One-line warning for a terminal that shrank while the client is running.
pub fn terminal_size_warning(columns: u16, rows: u16) -> Option<String> {
    if columns >= MIN_COLUMNS && rows >= MIN_ROWS {
        return None;
    }
    Some(format!(
        "WARNING: terminal is {columns}x{rows}; zagan.bet needs at least {MIN_COLUMNS}x{MIN_ROWS}. Resize to fit."
    ))
}

/// Render remembered hosts.
///
/// Two addresses that present the same certificate key are the same server, so
/// they are grouped under one fingerprint: `127.0.0.1:11525` and
/// `10.0.0.100:11525` reached through different networks still show as one
/// entry. Hosts without a fingerprint are never merged, since nothing proves
/// they are related.
pub fn host_lines(hosts: &[(String, Option<String>)]) -> Vec<String> {
    if hosts.is_empty() {
        return vec!["No remembered hosts.".to_string()];
    }

    let mut groups: Vec<(Option<&str>, Vec<&str>)> = Vec::new();
    for (host, fingerprint) in hosts {
        match fingerprint {
            Some(fingerprint) => {
                match groups
                    .iter_mut()
                    .find(|(key, _)| *key == Some(fingerprint.as_str()))
                {
                    Some((_, addresses)) => addresses.push(host),
                    None => groups.push((Some(fingerprint), vec![host])),
                }
            }
            // An unknown key proves nothing about identity.
            None => groups.push((None, vec![host])),
        }
    }

    let mut lines = vec!["Remembered hosts:".to_string()];
    for (fingerprint, addresses) in groups {
        lines.push(format!("  {}", addresses.join(", ")));
        match fingerprint {
            Some(fingerprint) => lines.push(format!("  fingerprint: {fingerprint}")),
            None => lines.push("  (no fingerprint)".to_string()),
        }
    }
    lines
}

/// Lines to move the cursor up to reach the first line of a region that ends
/// on the current line. `render()` has no trailing newline, so a 7-line board
/// needs `MoveUp(6)`.
pub fn lines_to_move_up(previous_lines: usize) -> u16 {
    previous_lines.saturating_sub(1).min(u16::MAX as usize) as u16
}

/// Column (0-based) to move to after the given prompt and input text.
pub fn input_cursor_column(prompt_len: usize, input_len: usize) -> u16 {
    prompt_len.saturating_add(input_len).min(u16::MAX as usize) as u16
}

/// Number of terminal rows a block of logical lines occupies after wrapping.
/// Empty lines still occupy one row.
pub fn visual_line_count(lines: &[String], width: usize) -> usize {
    let width = width.max(1);
    lines
        .iter()
        .map(|line| {
            let columns = display_width(line);
            if columns == 0 {
                1
            } else {
                columns.div_ceil(width)
            }
        })
        .sum()
}

/// Format a ping round-trip time with one decimal place.
pub fn format_pong(elapsed: std::time::Duration) -> String {
    format!("Pong ({:.1}ms)", elapsed.as_secs_f64() * 1000.0)
}