brink-runtime 0.0.6

//! Immutable linked program.

use std::collections::HashMap;

use brink_format::{CountingFlags, DefinitionId, ListValue, NameId, Value};

/// A linked, ready-to-execute program.
///
/// Created from [`StoryData`](brink_format::StoryData) via [`link()`](crate::link).
/// Immutable after creation — mutable per-instance state lives in [`Story`](crate::Story).
pub struct Program {
    pub(crate) containers: Vec<LinkedContainer>,
    /// Unified address map: `id → (container_idx, byte_offset)`.
    /// Contains both container IDs (offset 0) and intra-container addresses.
    pub(crate) address_map: HashMap<DefinitionId, (u32, usize)>,
    /// Scope `DefinitionId` for each entry in the line tables (parallel vec).
    /// Structural metadata — does not change with locale.
    pub(crate) scope_ids: Vec<DefinitionId>,
    /// CRC-32 checksum from the source `.inkb`, used for locale validation.
    pub(crate) source_checksum: u32,
    pub(crate) globals: Vec<GlobalSlot>,
    pub(crate) global_map: HashMap<DefinitionId, u32>,
    pub(crate) name_table: Vec<String>,
    /// Map from a knot/stitch path string to its target: the defining
    /// `DefinitionId` plus the resolved `(container_idx, byte_offset)`.
    /// Built at link time from named scope containers; lets consumers
    /// spawn flows at named entry points without needing `DefinitionId`s.
    pub(crate) address_by_path: HashMap<String, PathTarget>,
    pub(crate) root_idx: u32,
    /// List literal values referenced by `PushList(idx)`.
    pub(crate) list_literals: Vec<ListValue>,
    /// Per-item metadata keyed by item `DefinitionId`.
    pub(crate) list_item_map: HashMap<DefinitionId, ListItemEntry>,
    /// List definitions indexed by position.
    pub(crate) list_defs: Vec<ListDefEntry>,
    /// Map from list def `DefinitionId` to index in `list_defs`.
    pub(crate) list_def_map: HashMap<DefinitionId, usize>,
    /// External function metadata keyed by the external function's `DefinitionId`.
    pub(crate) external_fns: HashMap<DefinitionId, ExternalFnEntry>,
}

pub(crate) struct LinkedContainer {
    pub id: DefinitionId,
    pub bytecode: Vec<u8>,
    pub counting_flags: CountingFlags,
    pub path_hash: i32,
    /// Number of declared parameters (for arity-checking host-directed entry).
    pub param_count: u8,
    /// Index into `Program.line_tables` for this container's scope line table.
    pub scope_table_idx: u32,
}

pub(crate) struct GlobalSlot {
    #[expect(dead_code, reason = "needed for save/load serialization and debugging")]
    pub id: DefinitionId,
    pub name: NameId,
    pub default: Value,
}

/// Runtime metadata for a list item.
pub(crate) struct ListItemEntry {
    pub name: NameId,
    pub ordinal: i32,
    pub origin: DefinitionId,
}

/// Runtime metadata for a list definition.
pub(crate) struct ListDefEntry {
    pub name: NameId,
    /// All item `DefinitionId`s belonging to this list, sorted by ordinal.
    pub items: Vec<DefinitionId>,
}

/// Runtime metadata for an external function.
pub(crate) struct ExternalFnEntry {
    pub name: NameId,
    pub fallback: Option<DefinitionId>,
}

/// Resolved target of a qualified path string: the defining `DefinitionId`
/// (used for visit counting, exactly as a divert to the same target would
/// use it) plus the linked `(container_idx, byte_offset)` position.
#[derive(Debug, Clone, Copy)]
pub(crate) struct PathTarget {
    pub id: DefinitionId,
    pub container_idx: u32,
    pub byte_offset: usize,
}

impl Program {
    /// Resolve any target (container or address) to `(container_idx, byte_offset)`.
    pub(crate) fn resolve_target(&self, id: DefinitionId) -> Option<(u32, usize)> {
        self.address_map.get(&id).copied()
    }

    /// Resolve a definition ID to `(container_idx, byte_offset)`.
    #[cfg(feature = "testing")]
    pub fn resolve_address(&self, id: DefinitionId) -> Option<(u32, usize)> {
        self.resolve_target(id)
    }

    /// Get a container by its index.
    pub(crate) fn container(&self, idx: u32) -> &LinkedContainer {
        &self.containers[idx as usize]
    }

    /// Get a container's bytecode by index.
    #[cfg(feature = "testing")]
    pub fn container_bytecode(&self, idx: u32) -> &[u8] {
        &self.containers[idx as usize].bytecode
    }

    /// Number of containers.
    #[cfg(feature = "testing")]
    #[expect(
        clippy::cast_possible_truncation,
        reason = "container count fits in u32"
    )]
    pub fn container_count(&self) -> u32 {
        self.containers.len() as u32
    }

    /// CRC-32 checksum from the source `.inkb`, used for transcript validation.
    pub fn source_checksum(&self) -> u32 {
        self.source_checksum
    }

    /// Get the scope line table index for a container.
    pub(crate) fn scope_table_idx(&self, container_idx: u32) -> u32 {
        self.containers[container_idx as usize].scope_table_idx
    }

    /// Look up a name by id.
    pub(crate) fn name(&self, id: NameId) -> &str {
        &self.name_table[id.0 as usize]
    }

    /// Look up a global slot index.
    pub(crate) fn resolve_global(&self, id: DefinitionId) -> Option<u32> {
        self.global_map.get(&id).copied()
    }

    /// Get the root container index.
    pub(crate) fn root_idx(&self) -> u32 {
        self.root_idx
    }

    /// Resolve a qualified ink path to its `(container_idx, byte_offset)`.
    ///
    /// Supports knot names (`intro`), qualified stitches (`knot.stitch`), and,
    /// for programs compiled by `brink-compiler`, author labels
    /// (`knot.label`, `knot.stitch.label`). Programs without the compiler's
    /// `address_paths` table (legacy `.inkb` or converter output) resolve
    /// knot/stitch scope paths only. Use this to spawn flows at named entry
    /// points:
    ///
    /// ```ignore
    /// if let Some((idx, _)) = program.find_address("intro_scene") {
    ///     let (flow, ctx) = FlowInstance::new_at(program, idx);
    /// }
    /// ```
    #[must_use]
    pub fn find_address(&self, path: &str) -> Option<(u32, usize)> {
        self.address_by_path
            .get(path)
            .map(|t| (t.container_idx, t.byte_offset))
    }

    /// Resolve a qualified ink path to the `DefinitionId` of its target.
    /// Same path grammar as [`find_address`](Self::find_address). Used by
    /// `choose_path_string`, which needs the id so the jump goes through the
    /// same divert machinery (and visit counting) as `-> path` would.
    pub(crate) fn find_path_target(&self, path: &str) -> Option<DefinitionId> {
        self.address_by_path.get(path).map(|t| t.id)
    }

    /// Declared parameter count of the container a `path` targets, for
    /// arity-checking a host-directed parameterized entry. `None` if the path
    /// is unknown. (Always `0` for converter-built programs, which don't
    /// record param counts.)
    pub(crate) fn path_param_count(&self, path: &str) -> Option<u8> {
        self.address_by_path
            .get(path)
            .map(|t| self.containers[t.container_idx as usize].param_count)
    }

    /// Build the initial globals vector from slot defaults.
    pub fn global_defaults(&self) -> Vec<Value> {
        self.globals.iter().map(|s| s.default.clone()).collect()
    }

    /// Find the global variable slot index for a variable name, if declared.
    /// Used by host-facing variable get/set (`Story::variable`/`set_variable`).
    #[expect(clippy::cast_possible_truncation, reason = "global count fits in u32")]
    pub fn global_index(&self, name: &str) -> Option<u32> {
        self.globals
            .iter()
            .position(|slot| self.name(slot.name) == name)
            .map(|i| i as u32)
    }

    /// Get a list literal by index.
    pub(crate) fn list_literal(&self, idx: u16) -> &ListValue {
        &self.list_literals[idx as usize]
    }

    /// Look up a list item's metadata.
    pub(crate) fn list_item(&self, id: DefinitionId) -> Option<&ListItemEntry> {
        self.list_item_map.get(&id)
    }

    /// Get a list definition by its `DefinitionId`.
    pub(crate) fn list_def(&self, id: DefinitionId) -> Option<&ListDefEntry> {
        self.list_def_map.get(&id).map(|&idx| &self.list_defs[idx])
    }

    /// Find a list definition by its string name.
    pub(crate) fn list_def_by_name(&self, name: &str) -> Option<&ListDefEntry> {
        self.list_defs
            .iter()
            .find(|def| self.name(def.name) == name)
    }

    /// Look up an external function by its `DefinitionId`.
    pub(crate) fn external_fn(&self, id: DefinitionId) -> Option<&ExternalFnEntry> {
        self.external_fns.get(&id)
    }

    // ── Public variable introspection (host-facing) ─────────────────────────
    // `global_index` (above), `global_name`, and `global_count` form the
    // host-facing variable-introspection set used by `Story::variable`/
    // `set_variable` and consumers like the RMMZ var↔switch mapping. They were
    // previously `testing`-gated; promoted to public per the State View plan.

    /// Resolve a global slot index to its variable name.
    pub fn global_name(&self, idx: u32) -> Option<&str> {
        self.globals
            .get(idx as usize)
            .map(|slot| self.name(slot.name))
    }

    /// Number of global variable slots.
    #[expect(clippy::cast_possible_truncation, reason = "global count fits in u32")]
    pub fn global_count(&self) -> u32 {
        self.globals.len() as u32
    }

    // ── Debug introspection name lookups (used by `debug_snapshot`) ──────────

    /// Variable name for a global slot index.
    pub(crate) fn global_slot_name(&self, idx: usize) -> Option<&str> {
        self.globals.get(idx).map(|slot| self.name(slot.name))
    }

    /// Variable name for a global's defining `DefinitionId` (e.g. a
    /// `VariablePointer` target).
    pub(crate) fn global_var_name(&self, id: DefinitionId) -> Option<&str> {
        let slot = self.resolve_global(id)?;
        self.global_slot_name(slot as usize)
    }

    /// Display name for a list item by its `DefinitionId`.
    pub(crate) fn list_item_name(&self, id: DefinitionId) -> Option<&str> {
        self.list_item(id).map(|item| self.name(item.name))
    }
}

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

    fn make_program_with_named_containers(names: &[&str]) -> Program {
        // Build a minimal Program where each name maps to a unique
        // container_idx. Used to exercise find_address without going
        // through the full link path.
        let mut address_by_path = HashMap::new();
        for (i, name) in names.iter().enumerate() {
            #[expect(clippy::cast_possible_truncation, reason = "test fixture")]
            address_by_path.insert(
                (*name).to_string(),
                PathTarget {
                    id: DefinitionId::new(brink_format::DefinitionTag::Address, i as u64),
                    container_idx: i as u32,
                    byte_offset: 0,
                },
            );
        }
        Program {
            containers: Vec::new(),
            address_map: HashMap::new(),
            scope_ids: Vec::new(),
            source_checksum: 0,
            globals: Vec::new(),
            global_map: HashMap::new(),
            name_table: Vec::new(),
            address_by_path,
            root_idx: 0,
            list_literals: Vec::new(),
            list_item_map: HashMap::new(),
            list_defs: Vec::new(),
            list_def_map: HashMap::new(),
            external_fns: HashMap::new(),
        }
    }

    #[test]
    fn finds_known_knot() {
        let program = make_program_with_named_containers(&["intro", "outro"]);
        assert_eq!(program.find_address("intro"), Some((0, 0)));
        assert_eq!(program.find_address("outro"), Some((1, 0)));
    }

    #[test]
    fn returns_none_for_unknown_knot() {
        let program = make_program_with_named_containers(&["intro"]);
        assert_eq!(program.find_address("nope"), None);
    }

    #[test]
    fn empty_program_returns_none() {
        let program = make_program_with_named_containers(&[]);
        assert_eq!(program.find_address("anything"), None);
    }
}