//! The output half of the tui module: message blocks (`tui.success` & co.,
//! rendering in [`super::blocks`]), styled markup (`tui.styled` /
//! `tui.addPreset`, engine in [`super::markup`]), and the low-level
//! `tui.raw` / `tui.screenInfo` building blocks.

use std::io::IsTerminal;

use mlua::prelude::{LuaResult, LuaTable, LuaValue};
use mlua::Lua;

use super::opts::Opts;
use super::{blocks, ext_err, markup};

pub(super) fn colorize() -> bool {
    colored::control::SHOULD_COLORIZE.should_colorize()
}

/// Width blocks are rendered to: the terminal width capped at
/// [`blocks::MAX_LINE_LENGTH`], or the cap itself when there is no terminal.
fn terminal_line_length() -> usize {
    match crossterm::terminal::size() {
        Ok((w, _)) if w > 0 => (w as usize).min(blocks::MAX_LINE_LENGTH),
        _ => blocks::MAX_LINE_LENGTH,
    }
}

/// The block functions' first argument: one message or an array of messages
/// (rendered into the same block, separated by a blank line).
fn messages_arg(fname: &str, v: LuaValue) -> LuaResult<Vec<String>> {
    match v {
        LuaValue::String(s) => Ok(vec![
            s.to_str()
                .map_err(|_| ext_err!("{fname}: message must be valid UTF-8"))?
                .to_string(),
        ]),
        LuaValue::Table(t) => {
            let mut out = Vec::with_capacity(t.raw_len());
            for i in 1..=t.raw_len() {
                match t.raw_get::<LuaValue>(i)? {
                    LuaValue::String(s) => out.push(
                        s.to_str()
                            .map_err(|_| ext_err!("{fname}: message[{i}] must be valid UTF-8"))?
                            .to_string(),
                    ),
                    other => {
                        return Err(ext_err!(
                            "{fname}: message[{i}] must be a string (got {})",
                            other.type_name()
                        ))
                    }
                }
            }
            if out.is_empty() {
                return Err(ext_err!("{fname}: message must not be empty"));
            }
            Ok(out)
        }
        other => Err(ext_err!(
            "{fname}: message must be a string or an array of strings (got {})",
            other.type_name()
        )),
    }
}

/// The `style` option: same syntax as a markup tag body — a preset or
/// built-in name (`error`), an attribute spec (`fg=black;bg=green`), or
/// shorthand (`black;on-green`). Unlike markup (where a bad tag passes
/// through), a bad *argument* fails loudly.
fn style_opt(lua: &Lua, opts: &Opts, key: &str) -> LuaResult<Option<markup::Style>> {
    match opts.string(key)? {
        None => Ok(None),
        Some(spec) => {
            let resolved = match lua.app_data_ref::<markup::Presets>() {
                Some(presets) => markup::resolve_spec(&spec, &presets),
                None => markup::resolve_style_spec(&spec),
            };
            resolved
                .map(Some)
                .ok_or_else(|| ext_err!("{}: invalid style '{spec}'", opts.fname()))
        }
    }
}

/// The module's single stdout sink. In test builds output goes through
/// `print!` so the libtest harness can capture it — direct `stdout()` writes
/// bypass the capture and trash the test runner's output. In normal builds it
/// writes the bytes directly, ignores errors (a broken pipe must not panic
/// the runtime) and flushes (tui.raw is used for `\r` redraws mid-line).
pub(super) fn write_stdout(bytes: &[u8]) {
    #[cfg(test)]
    print!("{}", String::from_utf8_lossy(bytes));
    #[cfg(not(test))]
    {
        use std::io::Write;
        let mut out = std::io::stdout().lock();
        let _ = out.write_all(bytes);
        let _ = out.flush();
    }
}

/// Print a rendered block surrounded by blank lines (Symfony's block
/// spacing), best-effort like `print`.
fn print_block(lines: &[String]) {
    let mut out = String::with_capacity(lines.iter().map(|l| l.len() + 1).sum::<usize>() + 2);
    out.push('\n');
    for line in lines {
        out.push_str(line);
        out.push('\n');
    }
    out.push('\n');
    write_stdout(out.as_bytes());
}

/// The `[LABEL]` block presets (Symfony's SymfonyStyle block styles, labels
/// without decoration). `tui.block` is the generic form with no defaults.
struct BlockPreset {
    name: &'static str,
    fname: &'static str,
    label: Option<&'static str>,
    style: Option<&'static str>,
    prefix: &'static str,
    padding: bool,
}

const BLOCK_PRESETS: &[BlockPreset] = &[
    BlockPreset { name: "block", fname: "tui.block", label: None, style: None, prefix: " ", padding: false },
    BlockPreset { name: "success", fname: "tui.success", label: Some("OK"), style: Some("fg=black;bg=green"), prefix: " ", padding: true },
    BlockPreset { name: "error", fname: "tui.error", label: Some("ERROR"), style: Some("fg=white;bg=red"), prefix: " ", padding: true },
    BlockPreset { name: "warning", fname: "tui.warning", label: Some("WARNING"), style: Some("fg=black;bg=yellow"), prefix: " ", padding: true },
    BlockPreset { name: "caution", fname: "tui.caution", label: Some("CAUTION"), style: Some("fg=white;bg=red"), prefix: " ! ", padding: true },
    BlockPreset { name: "info", fname: "tui.info", label: Some("INFO"), style: Some("fg=green"), prefix: " ", padding: false },
    BlockPreset { name: "note", fname: "tui.note", label: Some("NOTE"), style: Some("fg=yellow"), prefix: " ! ", padding: false },
    BlockPreset { name: "comment", fname: "tui.comment", label: None, style: Some("fg=gray"), prefix: " ", padding: false },
];

/// The outlined-box presets. Titles are plain words (no emoji) and are only
/// fallbacks — `opts.title` overrides them.
struct OutlinePreset {
    name: &'static str,
    fname: &'static str,
    title: Option<&'static str>,
    style: Option<&'static str>,
}

const OUTLINE_PRESETS: &[OutlinePreset] = &[
    OutlinePreset { name: "outlineBlock", fname: "tui.outlineBlock", title: None, style: None },
    OutlinePreset { name: "outlineSuccess", fname: "tui.outlineSuccess", title: Some("Success"), style: Some("fg=green") },
    OutlinePreset { name: "outlineError", fname: "tui.outlineError", title: Some("Error"), style: Some("fg=red") },
    OutlinePreset { name: "outlineWarning", fname: "tui.outlineWarning", title: Some("Warning"), style: Some("fg=yellow") },
    OutlinePreset { name: "outlineNote", fname: "tui.outlineNote", title: Some("Note"), style: Some("fg=blue") },
    OutlinePreset { name: "outlineInfo", fname: "tui.outlineInfo", title: Some("Info"), style: Some("fg=green") },
    OutlinePreset { name: "outlineCaution", fname: "tui.outlineCaution", title: Some("Caution"), style: Some("fg=red") },
];

/// A preset style spec is a compile-time literal; parsing it cannot fail.
fn preset_style(spec: Option<&str>) -> Option<markup::Style> {
    spec.map(|s| markup::resolve_style_spec(s).expect("preset style spec is valid"))
}

/// A `tui.addPreset` name: identifier-like, so it can never collide with
/// attribute specs (which contain `=`) or be mistaken for a closing tag.
fn valid_preset_name(name: &str) -> bool {
    let mut chars = name.chars();
    chars.next().is_some_and(|c| c.is_ascii_alphabetic())
        && chars.all(|c| c.is_ascii_alphanumeric() || c == '-' || c == '_')
}

pub(super) fn install(lua: &Lua, tui: &LuaTable) -> LuaResult<()> {
    // Message blocks: tui.block + the [LABEL] presets. All print directly to
    // stdout (blank-line separated), like Symfony's SymfonyStyle.
    for p in BLOCK_PRESETS {
        tui.raw_set(
            p.name,
            lua.create_function(move |lua, (msg, opts): (LuaValue, Option<LuaTable>)| {
                let opts = Opts::parse(p.fname, opts, &["label", "style", "prefix", "padding"])?;
                let messages = messages_arg(p.fname, msg)?;
                let cfg = blocks::BlockCfg {
                    label: opts.string("label")?.or_else(|| p.label.map(str::to_string)),
                    style: style_opt(lua, &opts, "style")?.or_else(|| preset_style(p.style)),
                    prefix: opts.string("prefix")?.unwrap_or_else(|| p.prefix.to_string()),
                    padding: opts.boolean("padding")?.unwrap_or(p.padding),
                };
                print_block(&blocks::render_block(
                    &messages,
                    &cfg,
                    terminal_line_length(),
                    colorize(),
                ));
                Ok(())
            })?,
        )?;
    }

    // Outlined boxes: tui.outlineBlock + presets. opts.title overrides the
    // preset's fallback title.
    for p in OUTLINE_PRESETS {
        tui.raw_set(
            p.name,
            lua.create_function(move |lua, (msg, opts): (LuaValue, Option<LuaTable>)| {
                let opts = Opts::parse(p.fname, opts, &["title", "style", "padding"])?;
                let messages = messages_arg(p.fname, msg)?;
                let title = opts.string("title")?.or_else(|| p.title.map(str::to_string));
                let style = style_opt(lua, &opts, "style")?.or_else(|| preset_style(p.style));
                let padding = opts.boolean("padding")?.unwrap_or(true);
                print_block(&blocks::render_outline_block(
                    &messages,
                    title.as_deref(),
                    style.as_ref(),
                    padding,
                    terminal_line_length(),
                    colorize(),
                ));
                Ok(())
            })?,
        )?;
    }

    // tui.styled: render markup to an ANSI string (or plain text when colors
    // are off — pipes, NO_COLOR).
    tui.raw_set(
        "styled",
        lua.create_function(|lua, v: LuaValue| {
            let s = match v {
                LuaValue::String(s) => s,
                other => {
                    return Err(ext_err!(
                        "tui.styled: expected a string (got {})",
                        other.type_name()
                    ))
                }
            };
            let s = s
                .to_str()
                .map_err(|_| ext_err!("tui.styled: input must be valid UTF-8"))?;
            let presets = lua
                .app_data_ref::<markup::Presets>()
                .ok_or_else(|| ext_err!("tui.styled: preset registry missing"))?;
            Ok(markup::render(&s, colorize(), &presets))
        })?,
    )?;

    // tui.escape: backslash-escape the markup metacharacters so untrusted
    // text (user input, API data) can be embedded in a tui.styled format
    // string and come out verbatim.
    tui.raw_set(
        "escape",
        lua.create_function(|_, v: LuaValue| {
            let s = match v {
                LuaValue::String(s) => s,
                other => {
                    return Err(ext_err!(
                        "tui.escape: expected a string (got {})",
                        other.type_name()
                    ))
                }
            };
            let s = s
                .to_str()
                .map_err(|_| ext_err!("tui.escape: input must be valid UTF-8"))?;
            Ok(markup::escape(&s))
        })?,
    )?;

    // tui.addPreset: register a custom markup tag, e.g.
    // addPreset("keyword", "fg=white;bg=magenta") makes <keyword>…</keyword>
    // work in tui.styled and as a block `style` option. The spec may also
    // reference an existing preset or built-in. Re-registering a name
    // overwrites it; built-in names can be shadowed.
    tui.raw_set(
        "addPreset",
        lua.create_function(|lua, (name, spec): (LuaValue, LuaValue)| {
            const F: &str = "tui.addPreset";
            let name = match name {
                LuaValue::String(s) => s
                    .to_str()
                    .map_err(|_| ext_err!("{F}: name must be valid UTF-8"))?
                    .to_string(),
                other => {
                    return Err(ext_err!("{F}: name must be a string (got {})", other.type_name()))
                }
            };
            if !valid_preset_name(&name) {
                return Err(ext_err!(
                    "{F}: name must start with a letter and contain only letters, digits, '-' or '_' (got '{name}')"
                ));
            }
            let spec = match spec {
                LuaValue::String(s) => s
                    .to_str()
                    .map_err(|_| ext_err!("{F}: style must be valid UTF-8"))?
                    .to_string(),
                other => {
                    return Err(ext_err!("{F}: style must be a string (got {})", other.type_name()))
                }
            };
            let mut presets = lua
                .app_data_mut::<markup::Presets>()
                .ok_or_else(|| ext_err!("{F}: preset registry missing"))?;
            let style = markup::resolve_spec(&spec, &presets)
                .ok_or_else(|| ext_err!("{F}: invalid style '{spec}'"))?;
            presets.0.insert(name, style);
            Ok(())
        })?,
    )?;

    // tui.raw: write to stdout with no newline and no separator (io.write
    // semantics) and flush — the building block for progress-style output
    // (`tui.raw("\rprogress: 50%")`). Values go through tostring; byte
    // strings pass through unmodified.
    tui.raw_set(
        "raw",
        lua.create_function(|lua, args: mlua::Variadic<LuaValue>| {
            let tostring: mlua::Function = lua.globals().get("tostring")?;
            let mut out = Vec::new();
            for v in args {
                let s = tostring.call::<mlua::String>(v)?;
                out.extend_from_slice(&s.as_bytes());
            }
            write_stdout(&out);
            Ok(())
        })?,
    )?;

    // tui.screenInfo: terminal facts for scripts that render their own UI
    // (progress bars, right-aligned text, …). width/height are nil when
    // there is no terminal to measure.
    tui.raw_set(
        "screenInfo",
        lua.create_function(|lua, ()| {
            let t = lua.create_table()?;
            // Some ptys report 0x0; treat that as "unknown", like no terminal.
            if let Ok((w, h)) = crossterm::terminal::size()
                && w > 0
                && h > 0
            {
                t.raw_set("width", w)?;
                t.raw_set("height", h)?;
            }
            t.raw_set("tty", std::io::stdout().is_terminal())?;
            t.raw_set("colors", colorize())?;
            Ok(t)
        })?,
    )?;

    Ok(())
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn preset_name_validation() {
        // Names that shadow shorthand tokens ("red", "on-red") are allowed —
        // shadowing is the user's explicit, documented choice.
        for ok in ["keyword", "a", "warn2", "my-tag", "my_tag", "B", "red", "on-red"] {
            assert!(valid_preset_name(ok), "{ok} should be valid");
        }
        for bad in ["", "2fast", "-x", "fg=red", "a;b", "a b", "žluť"] {
            assert!(!valid_preset_name(bad), "{bad} should be invalid");
        }
    }
}