//! Font objects: a `<Font name=…>` or a `CreateFont` font is a Lua object, published as the global
//! of its name with its own method table. Stock FrameXML never calls this API; addons do.
//!
//! The reference's class is `CSimpleFont` (`0x87a454`). Its method table (`0x87c7c8`) has 22
//! entries (`mov edx,0x16` at `0x7a10d5`), and its lookup `0x7a1100` has no base-class fallback.
//! All are here but the `SetSpacing` pair ([`install`]); `CopyFontObject` is the one a FontString
//! lacks. A named font is published by `0x783870` through `SetName 0x784150` and `CreateLuaHandle
//! 0x701bd0`, which leaves a non-nil `_G[name]` alone (`0x701cb8`).
//!
//! A setter repaints every FontString that inherits the font. The reference links dependents into
//! the font's list (`+0x74`/`+0x78`) and each setter ends in `NotifyDependents 0x784180`, calling
//! `OnFontChanged` (`0x77e4b0` on a font, `0x773530` then `0x770800` on a FontString); here each
//! setter writes the [`FontObject`] and calls [`propagate`]. A local setter clears its property's
//! bit in the dependent's inherit mask (`+0x2c`, FontString `+0xd4`) and nothing restores it, so a
//! colour set on a FontString survives a later `SetFontObject`: [`RegionData::font_explicit`] is
//! that mask. `+0x38` is not it; its high bits mark a held value, which the inheriting merge also
//! sets (`0x7709d3`).
//!
//! Not built: a `<Font inherits=…>` chain is flattened at load (`Loader::do_font`), so mutating
//! `MasterFont` does not reach `GameFontNormal`, where the reference links it live: `LoadXML
//! 0x783c30` calls the `SetFontObject` link `0x770c60` for `inherits=` (`0x783ce6`) and `font=`
//! (`0x783d22`). No corpus addon mutates a declared font object.

use mlua::{Lua, Table, Value};

use super::binding_abi;
use super::object::publish_global;
use crate::justify;

use super::{FontObject, FontShadow, Model, Outline, RegionData};

/// The shared metatable of every font-object handle.
const REG_FONT_META: &str = "__benilla_font_meta";
/// The font-object method table, which is the metatable's `__index`.
const REG_FONT_METHODS: &str = "__benilla_font_methods";
/// name → handle, so `GameFontNormal == GameFontNormal` and a re-declared `<Font>` keeps identity.
const REG_FONT_WRAPPERS: &str = "__benilla_font_wrappers";

// ── The handle ───────────────────────────────────────────────────────────────────────────────

/// Get or create the Lua handle for a named font object. Keyed by name, which every font has (an
/// unnamed `<Font>` is dropped at parse), so a re-declared `<Font>` updates its record in place.
///
/// `T[0]` holds the name, not a frame id, so a font handle passed where a frame is wanted is
/// rejected rather than decoded.
pub(crate) fn wrapper(lua: &Lua, name: &str) -> mlua::Result<Table> {
    let wrappers: Table = lua.named_registry_value(REG_FONT_WRAPPERS)?;
    if let Value::Table(t) = wrappers.get::<Value>(name)? {
        return Ok(t);
    }
    let t = lua.create_table()?;
    t.raw_set(0, name)?;
    let meta: Table = lua.named_registry_value(REG_FONT_META)?;
    t.set_metatable(Some(meta))?;
    wrappers.set(name, t.clone())?;
    Ok(t)
}

/// Publish the handle as `_G[name]`, leaving a non-nil global alone as [`publish_global`] does.
pub(crate) fn publish(lua: &Lua, name: &str) -> mlua::Result<()> {
    let t = wrapper(lua, name)?;
    publish_global(lua, name, &t)
}

/// The name a font handle holds in `T[0]`.
fn name_of(this: &Table) -> mlua::Result<String> {
    match this.raw_get::<Value>(0)? {
        Value::String(s) => Ok(s.to_str()?.to_string()),
        _ => Err(mlua::Error::runtime(
            "not a font object (missing T[0] name identity)",
        )),
    }
}

/// A font argument as a registry name, `None` for nil: an object, a name or nil, the three forms of
/// the reference's usage `SetFontObject(font or "font" or nil)` (`0x87c5cc`). Anything else
/// raises, as the reference's `luaL_error 0x6f4940` does.
pub(super) fn resolve(verb: &str, v: &Value) -> mlua::Result<Option<String>> {
    match v {
        Value::Nil => Ok(None),
        Value::Table(t) => name_of(t).map(Some).map_err(|_| {
            mlua::Error::runtime(format!(
                "{verb}: the argument is a table but not a font object \
                 (a frame or region cannot be a font)"
            ))
        }),
        Value::String(s) => Ok(Some(s.to_str()?.to_string())),
        other => Err(mlua::Error::runtime(format!(
            "{verb}: expected a font object, a font name, or nil, got {}",
            other.type_name()
        ))),
    }
}

/// [`resolve`] refusing nil, for `CopyFontObject`, which has nothing to copy from (`0x7a01b0`).
fn resolve_required(verb: &str, v: &Value) -> mlua::Result<String> {
    resolve(verb, v)?.ok_or_else(|| {
        mlua::Error::runtime(format!(
            "{verb}: expected a font object or a font name, got nil"
        ))
    })
}

// ── The live link: a font object to the regions that inherit it ──────────────────────────────

/// Copy a font object's paint onto one region, skipping each property the region set itself
/// ([`RegionData::font_explicit`]) and each the font does not hold: the reference gates every merge
/// on the source's held-value bits (`+0x38`, the merge `0x770910`), so an empty `CreateFont` font
/// changes nothing.
///
/// The outline is always copied, as [`Outline`] has no unset state; only an empty `CreateFont` font
/// on an outlined FontString differs from the reference, clearing the outline.
pub(crate) fn repaint(d: &mut RegionData, fo: &FontObject) {
    let ex = d.font_explicit;
    if !ex.face {
        if let Some(f) = &fo.font {
            d.font_path = Some(f.clone());
        }
    }
    if !ex.height {
        if let Some(h) = fo.height {
            d.font_height = Some(h);
        }
    }
    if !ex.outline {
        d.outline = fo.outline;
    }
    if !ex.shadow {
        if let Some(s) = fo.shadow {
            d.font_shadow = Some(s);
        }
    }
    if !ex.color {
        if let Some(c) = fo.color {
            d.vertex_color = Some(c);
        }
    }
    if !ex.justify_h {
        if let Some(j) = fo.justify_h {
            d.justify.set_h(j);
        }
    }
    if !ex.justify_v {
        if let Some(j) = fo.justify_v {
            d.justify.set_v(j);
        }
    }
}

/// Repaint every region that inherits `name`, as the reference's live parent link does. Linear in
/// regions: font-object setters are addon configuration, never per frame. Button state fonts are
/// stored by name and re-resolved at every `extract`, so they need no push.
pub(crate) fn propagate(model: &mut Model, name: &str) {
    let Some(fo) = model.font_object(name).cloned() else {
        return;
    };
    for d in model.region_data.values_mut() {
        if d.font_object.as_deref() == Some(name) {
            repaint(d, &fo);
        }
    }
    // A fan-out cannot name its regions without a second pass, so every region is re-measured.
    model.touch_measure_all();
}

/// Run `f` on the named font object's record, then [`propagate`]: every setter's one write path.
fn edit<R>(lua: &Lua, this: &Table, f: impl FnOnce(&mut FontObject) -> R) -> mlua::Result<R> {
    let name = name_of(this)?;
    let mut model = lua.app_data_mut::<Model>().expect("model");
    let out = f(model
        .font_objects_by_lower
        .entry(name.to_ascii_lowercase())
        .or_default());
    propagate(&mut model, &name);
    Ok(out)
}

/// A copy of the named font object's record.
fn read(lua: &Lua, this: &Table) -> mlua::Result<FontObject> {
    let name = name_of(this)?;
    let model = lua.app_data_ref::<Model>().expect("model");
    Ok(model.font_object(&name).cloned().unwrap_or_default())
}

// ── install: the method table, the metatable and CreateFont ──────────────────────────────────

/// Build the font-object method table and metatable, and register `CreateFont`.
///
/// Deviation: `SetSpacing`/`GetSpacing` are absent, because nothing renders line spacing (the line
/// pitch is the font height): a missing method raises and names itself, where a stored, undrawn
/// value would fail silently.
pub(super) fn install(lua: &Lua) -> mlua::Result<()> {
    lua.set_named_registry_value(REG_FONT_WRAPPERS, lua.create_table()?)?;

    let m = lua.create_table()?;

    // ── identity ────────────────────────────────────────────────────────────────────────────
    m.set(
        "GetObjectType",
        lua.create_function(|_, _this: Table| Ok("Font"))?,
    )?;
    // `1` or nil, never a boolean, like the Region's (`0x7a1290`): the Font's own `IsObjectType`
    // (`0x79fe60`) answers a number. Its argument handling is untraced; mlua's coercion applies.
    m.set(
        "IsObjectType",
        lua.create_function(|_, (_this, ty): (Table, String)| {
            Ok(binding_abi::flag(ty.eq_ignore_ascii_case("font")))
        })?,
    )?;
    m.set(
        "GetName",
        lua.create_function(|_, this: Table| name_of(&this))?,
    )?;

    // ── the font-object-on-font-object pair ─────────────────────────────────────────────────
    // SetFontObject(other): on a Font, the same copy as CopyFontObject, since Font chains are
    // flattened (module doc); nil is a no-op, with no link to sever.
    m.set(
        "SetFontObject",
        lua.create_function(|lua, (this, other): (Table, Value)| {
            match resolve("SetFontObject", &other)? {
                Some(_) => copy_from(lua, &this, &other, "SetFontObject"),
                None => Ok(()),
            }
        })?,
    )?;
    // CopyFontObject(other): refuses nil (`0x7a01b0` value-copies and re-parents).
    m.set(
        "CopyFontObject",
        lua.create_function(|lua, (this, other): (Table, Value)| {
            resolve_required("CopyFontObject", &other)?;
            copy_from(lua, &this, &other, "CopyFontObject")
        })?,
    )?;
    // GetFontObject(): always nil; with Font chains flattened, a Font has no parent link.
    m.set(
        "GetFontObject",
        lua.create_function(|_, _this: Table| Ok(Value::Nil))?,
    )?;

    // ── face ────────────────────────────────────────────────────────────────────────────────
    // SetFont(path, height [, flags]) → 1, or nil when the font file fails to load, which does not
    // raise. Deviation: any non-empty path answers 1, because the atlas falls back per face and no
    // load fails; an empty one answers nil.
    m.set(
        "SetFont",
        lua.create_function(
            |lua, (this, file, height, flags): (Table, Value, Value, Option<String>)| {
                // The argument gate the FontString and EditBox tables share (`0x79f210`); a
                // missing argument raises (`0x87c69c`).
                let (path, height) = super::font_block::set_font_args(&file, &height, "Font")?;
                let ok = !path.is_empty();
                edit(lua, &this, |fo| {
                    if ok {
                        fo.font = Some(path);
                    }
                    fo.height = Some(height);
                    if let Some(f) = flags {
                        // The Lua flag spelling (`OUTLINE`, `THICKOUTLINE`), not the XML
                        // attribute's (`NORMAL`, `THICK`).
                        fo.outline = Outline::flags(&f);
                    }
                })?;
                Ok(if ok { Value::Number(1.0) } else { Value::Nil })
            },
        )?,
    )?;
    // GetFont() → path, height, flags. An unset Font answers nil, 0, "": the constructor
    // `0x783a40` zeroes the height and stores a NULL path (`0x41e3a0`), which pushes as nil.
    m.set(
        "GetFont",
        lua.create_function(|lua, this: Table| {
            let fo = read(lua, &this)?;
            let path = match fo.font {
                Some(p) => Value::String(lua.create_string(&p)?),
                None => Value::Nil,
            };
            Ok((path, fo.height.unwrap_or(0.0), fo.outline.as_str()))
        })?,
    )?;

    // ── colour, and the alpha that is its fourth channel ────────────────────────────────────
    // Shape C on r, g, b (`SetTextColor 0x79f4d0`): nil or a non-number is 0, never a raise.
    m.set(
        "SetTextColor",
        lua.create_function(
            |lua, (this, r, g, b, a): (Table, Value, Value, Value, Option<f32>)| {
                let (r, g, b) = (
                    super::object::as_f32(&r),
                    super::object::as_f32(&g),
                    super::object::as_f32(&b),
                );
                edit(lua, &this, |fo| {
                    let keep = fo.color.map_or(1.0, |c| c[3]);
                    fo.color = Some([r, g, b, a.unwrap_or(keep)]);
                })
            },
        )?,
    )?;
    m.set(
        "GetTextColor",
        lua.create_function(|lua, this: Table| {
            let c = read(lua, &this)?.color.unwrap_or([1.0, 1.0, 1.0, 1.0]);
            Ok((c[0], c[1], c[2], c[3]))
        })?,
    )?;
    // SetAlpha/GetAlpha are the text colour's alpha: a FontInstance has one packed colour
    // (`+0x58`) and no alpha of its own.
    m.set(
        "SetAlpha",
        lua.create_function(|lua, (this, a): (Table, f32)| {
            edit(lua, &this, |fo| {
                let c = fo.color.unwrap_or([1.0, 1.0, 1.0, 1.0]);
                fo.color = Some([c[0], c[1], c[2], a]);
            })
        })?,
    )?;
    m.set(
        "GetAlpha",
        lua.create_function(|lua, this: Table| Ok(read(lua, &this)?.color.map_or(1.0, |c| c[3])))?,
    )?;

    // ── shadow ──────────────────────────────────────────────────────────────────────────────
    m.set(
        "SetShadowColor",
        lua.create_function(
            // Shape C on r, g, b (`Font:SetShadowColor 0x79f730`): never raises.
            |lua, (this, r, g, b, a): (Table, Value, Value, Value, Option<f32>)| {
                let (r, g, b) = (
                    crate::script::object::as_f32(&r),
                    crate::script::object::as_f32(&g),
                    crate::script::object::as_f32(&b),
                );
                edit(lua, &this, |fo| {
                    let offset = fo.shadow.map_or([0.0, 0.0], |s| s.offset);
                    fo.shadow = Some(FontShadow {
                        offset,
                        color: [r, g, b, a.unwrap_or(1.0)],
                    });
                })
            },
        )?,
    )?;
    m.set(
        "GetShadowColor",
        lua.create_function(|lua, this: Table| {
            let c = read(lua, &this)?
                .shadow
                .map_or([0.0, 0.0, 0.0, 1.0], |s| s.color);
            Ok((c[0], c[1], c[2], c[3]))
        })?,
    )?;
    m.set(
        "SetShadowOffset",
        lua.create_function(|lua, (this, x, y): (Table, f32, f32)| {
            edit(lua, &this, |fo| {
                let color = fo.shadow.map_or([0.0, 0.0, 0.0, 1.0], |s| s.color);
                fo.shadow = Some(FontShadow {
                    offset: [x, y],
                    color,
                });
            })
        })?,
    )?;
    m.set(
        "GetShadowOffset",
        lua.create_function(|lua, this: Table| {
            let o = read(lua, &this)?.shadow.map_or([0.0, 0.0], |s| s.offset);
            Ok((o[0], o[1]))
        })?,
    )?;

    // ── justification ───────────────────────────────────────────────────────────────────────
    // Parsing is [`crate::justify`]'s, shared with the FontString pair: `SStrCmpI` over the whole
    // string, no trim. `None` means the font does not specify the axis (inheritance), not a
    // cleared axis; a fresh object reads CENTER/MIDDLE, the constructor default `0x212`.
    m.set(
        "SetJustifyH",
        lua.create_function(|lua, (this, j): (Table, String)| {
            let jh = match justify::parse_h(&j) {
                justify::Set::To(jh) => jh,
                justify::Set::Clears => return Ok(()),
                justify::Set::NoMatch => return Err(justify::usage_h("Font")),
            };
            edit(lua, &this, |fo| fo.justify_h = Some(jh))
        })?,
    )?;
    m.set(
        "GetJustifyH",
        lua.create_function(|lua, this: Table| {
            Ok(justify::name_h(
                read(lua, &this)?.justify_h.unwrap_or_default(),
            ))
        })?,
    )?;
    m.set(
        "SetJustifyV",
        lua.create_function(|lua, (this, j): (Table, String)| {
            let jv = match justify::parse_v(&j) {
                justify::Set::To(jv) => jv,
                justify::Set::Clears => return Ok(()),
                justify::Set::NoMatch => return Err(justify::usage_v("Font")),
            };
            edit(lua, &this, |fo| fo.justify_v = Some(jv))
        })?,
    )?;
    m.set(
        "GetJustifyV",
        lua.create_function(|lua, this: Table| {
            Ok(justify::name_v(
                read(lua, &this)?.justify_v.unwrap_or_default(),
            ))
        })?,
    )?;

    let meta = lua.create_table()?;
    // `__index` is the method table itself, not a function: a table index costs ~9 ns against
    // ~200 ns through a Rust dispatcher, and nothing mutates the table after this point.
    meta.set("__index", m.clone())?;
    lua.set_named_registry_value(REG_FONT_METHODS, m)?;
    lua.set_named_registry_value(REG_FONT_META, meta)?;

    lua.globals()
        .set("CreateFont", lua.create_function(create_font)?)?;
    Ok(())
}

/// `SetFontObject`/`CopyFontObject` on a Font: take the other object's paint wholesale.
fn copy_from(lua: &Lua, this: &Table, other: &Value, verb: &str) -> mlua::Result<()> {
    let src = resolve_required(verb, other)?;
    let paint = {
        let model = lua.app_data_ref::<Model>().expect("model");
        model.font_object(&src).cloned().ok_or_else(|| {
            mlua::Error::runtime(format!(
                "{verb}: no font object named '{src}' is registered"
            ))
        })?
    };
    edit(lua, this, |fo| *fo = paint)
}

/// `CreateFont(name)`: mint a font object, publish it as the global `name` and return it; addons
/// use both. An existing name returns that object unchanged and unrepublished (`0x7839ab`).
///
/// The reference's gate (`0x706048`) takes a number or any string, the empty one included, and
/// raises on anything else. A fresh object holds nothing, so it copies nothing ([`repaint`]).
fn create_font(lua: &Lua, name: Option<String>) -> mlua::Result<Table> {
    let name = name.ok_or_else(|| {
        mlua::Error::runtime("CreateFont: a font name is required (it becomes a global)")
    })?;
    {
        let mut model = lua.app_data_mut::<Model>().expect("model");
        model
            .font_objects_by_lower
            .entry(name.to_ascii_lowercase())
            .or_default();
    }
    let t = wrapper(lua, &name)?;
    publish_global(lua, &name, &t)?;
    Ok(t)
}