//! The `aura graph` ASCII-DAG adapter (#13, #38): turns the engine's
//! graph-as-data (C9) into an `ascii_dag::Graph` rendered to a `String`. Two
//! views. `render_blueprint` shows the authored structure — a flat main graph
//! wiring the harness with each composite as a single opaque node, plus a
//! `where:` section that defines each distinct composite type once (its interior
//! with `[<name>]` input/output port markers). `render_compilat` shows the flat
//! post-inline graph (boundaries dissolved, C23). Rendering reads structure +
//! node `label()`s only — never `eval`.
//!
//! ascii-dag borrows its node labels as `&'a str`, so each function first
//! materializes the owned label `String`s (which outlive the `Graph`), then
//! borrows into them. `RenderMode::Vertical` is mandatory: Horizontal collapses a
//! fan-out onto one path. Both views build flat graphs (no subgraphs): the
//! subgraph layout mis-centres wide sibling labels, the flat layout does not.

use ascii_dag::graph::{Graph, RenderMode};
use ascii_dag::render::colors::Palette;
use aura_core::{Node, PrimitiveBuilder, ScalarKind};
use aura_engine::{
    aliases_on, signature_of, BlueprintNode, Composite, Edge, OutField, ParamAlias, SourceSpec,
    Target,
};

/// Where a leaf's param **names** come from in the shared leaf-label path — the one
/// border that differs between the two views (#48). A composite interior leaf draws
/// its names from the composite's `ParamAlias` overlay (filtered to this node,
/// keeping the existing `where:` form byte-for-byte); a top-level blueprint leaf has
/// no alias overlay, so its names come straight from the factory's declared params.
enum ParamNames<'a> {
    /// Composite interior: the alias list, filtered by `node == index` (existing
    /// `where:` behaviour — only aliased slots show, never factory defaults).
    Aliases(&'a [ParamAlias]),
    /// Top-level blueprint leaf: every factory-declared param name, in order.
    Factory,
}

/// A CLI-local, *borrowed* render notion unifying a composite **input role** and a
/// blueprint **bound source role** for the shared graph core (#48): both are an
/// external entry drawn as a marker node wired into its interior `targets`. Both
/// views build these from `Role` (name = role name); the blueprint root filters to
/// bound roles (`source.is_some()`), the only remaining root-vs-interior
/// distinction (C3) — no engine change, the list is assembled CLI-side and borrows
/// the engine's `Target` slices.
struct Entry<'a> {
    name: String,
    targets: &'a [Target],
}

/// Edge colouring for a rendered graph. `Plain` is monochrome — golden-stable and
/// pipe-safe (no escape codes when redirected to a file). `Ansi` emits per-edge
/// ANSI colours so crossing edges stay traceable on an interactive terminal. The
/// CLI selects `Ansi` only when stdout is a TTY; tests always render `Plain`.
#[derive(Clone, Copy, PartialEq, Eq, Debug)]
pub enum Color {
    Plain,
    Ansi,
}

/// Blueprint view: the authored structure (#38). A flat main graph wires the
/// harness with each composite shown as a single opaque node; a `where:` section
/// defines each distinct composite type once. Flat layout only (no subgraphs).
pub fn render_blueprint(bp: &Composite, color: Color) -> String {
    // the main graph is the shared graph core (`render_graph`) over the root
    // composite's top-level (nodes, edges), rendered exactly as a `where:` interior:
    // leaves enriched (param names, a `<field> →` prefix for a multi-output producer
    // — macd's `histogram` driving Exposure — and, now threaded at the root too,
    // fan-in slot stubs), composites opaque, entries named by their role. The only
    // deltas vs a composite definition: param names come from the builder (no alias
    // overlay at the root); entries are filtered to bound source roles (C3); there
    // is no output record (terminals are sinks) and no title.
    let entries: Vec<Entry> = bp
        .input_roles()
        .iter()
        .filter(|role| role.source.is_some())
        .map(|role| Entry { name: role.name.clone(), targets: &role.targets })
        .collect();
    let main = render_graph(
        bp.nodes(),
        bp.edges(),
        &entries,
        &[], // no output bindings: a blueprint's terminals are sinks
        ParamNames::Factory,
        bp, // the root IS the fan-in stub context (it carries roles + edges)
        None, // no title
        color,
    );

    // definitions: each distinct composite type, once, recursively.
    let defs = collect_distinct_composites(bp);
    if defs.is_empty() {
        return main;
    }
    let body = defs.iter().map(|c| render_definition(c, color)).collect::<Vec<_>>().join("\n");
    format!("{main}\nwhere:\n\n{body}")
}

/// The shared graph core both views render through (#48): a flat ascii-dag of the
/// computation DAG plus external-entry markers. `nodes`/`edges` are a borrowed
/// (blueprint-root or composite-interior) graph slice — never an owned
/// `Composite` (`PrimitiveBuilder` is not `Clone`). Each leaf gets the unified
/// [`leaf_label`]; each composite is opaque (`[name]`); a producing node carrying an
/// `OutField` re-export gets the `name := ` binding prefix folded on (empty list →
/// no binding, the blueprint case); every [`Entry`] is drawn as a marker wired to its
/// interior targets. A `title` (the composite's typed signature) is prefixed when
/// `Some`. The render-border that differs — the param-name source — is passed as
/// `param_names`; `stub_ctx` is the borrowed composite (root or interior) both
/// views thread for fan-in slot resolution.
#[allow(clippy::too_many_arguments)]
fn render_graph(
    nodes: &[BlueprintNode],
    edges: &[Edge],
    entries: &[Entry],
    output: &[OutField],
    param_names: ParamNames,
    stub_ctx: &Composite,
    title: Option<&str>,
    color: Color,
) -> String {
    let mut labels: Vec<String> = Vec::with_capacity(nodes.len());
    for (i, item) in nodes.iter().enumerate() {
        let base = match item {
            BlueprintNode::Primitive(factory) => {
                leaf_label(nodes, edges, entries, i, factory, &param_names, stub_ctx)
            }
            BlueprintNode::Composite(c) => c.name().to_string(),
        };
        labels.push(match output_binding(output, i) {
            Some(prefix) => format!("{prefix}{base}"),
            None => base,
        });
    }

    let mut edge_pairs: Vec<(usize, usize)> = edges.iter().map(|e| (e.from, e.to)).collect();
    for entry in entries {
        let entry_id = labels.len();
        labels.push(entry.name.clone());
        for t in entry.targets {
            edge_pairs.push((entry_id, t.node));
        }
    }
    // outputs are folded onto their producers by output_binding above — no
    // standalone output node and no producer→output edge (C23).

    let flat = render_flat(&labels, &edge_pairs, color);
    match title {
        Some(t) => format!("{t}:\n\n{flat}"),
        None => flat,
    }
}

/// Build and render a flat (no-subgraph) ascii-dag graph from owned labels and
/// edge pairs — the same idiom `render_compilat` uses.
fn render_flat(labels: &[String], edges: &[(usize, usize)], color: Color) -> String {
    let mut g = Graph::with_mode(RenderMode::Vertical);
    for (id, l) in labels.iter().enumerate() {
        g.add_node(id, l);
    }
    for &(from, to) in edges {
        g.add_edge(from, to, None);
    }
    match color {
        Color::Plain => g.render(),
        // colour lives in the layout IR's scanline pass; node labels stay default
        // colour (ascii-dag only colours edges), so the box text is unaffected.
        Color::Ansi => g.compute_layout().render_scanline_colored(Palette::Ansi),
    }
}

/// Every distinct composite type in the blueprint, in first-seen order, keyed by
/// `name()` (the authoring type identity — same name implies same structure).
/// Recurses into a composite's interior on first sight so nested composites get
/// their own definition; a later same-name occurrence is skipped (deduped).
fn collect_distinct_composites(bp: &Composite) -> Vec<&Composite> {
    fn walk<'a>(items: &'a [BlueprintNode], seen: &mut Vec<&'a str>, out: &mut Vec<&'a Composite>) {
        for item in items {
            if let BlueprintNode::Composite(c) = item
                && !seen.contains(&c.name())
            {
                seen.push(c.name());
                out.push(c);
                walk(c.nodes(), seen, out);
            }
        }
    }
    let mut seen: Vec<&str> = Vec::new();
    let mut out: Vec<&Composite> = Vec::new();
    walk(bp.nodes(), &mut seen, &mut out);
    out
}

/// `ScalarKind` as a lowercase type string for a signature (`i64`/`f64`/`bool`/
/// `timestamp`). The derived `Debug` gives PascalCase (`I64`), so this is explicit.
fn kind_str(kind: ScalarKind) -> &'static str {
    match kind {
        ScalarKind::I64 => "i64",
        ScalarKind::F64 => "f64",
        ScalarKind::Bool => "bool",
        ScalarKind::Timestamp => "timestamp",
    }
}

/// The composite's typed signature for the definition title:
/// `name(p1:kind, …) -> (o1, …)`. Param kinds come from the aliased interior leaf's
/// declared params; output **names only** (kinds need a pre-build factory interface,
/// #43). An empty alias list renders `name()`. Total: a malformed alias falls back
/// to `?` rather than panicking (compile is the validator, #41).
fn signature(c: &Composite) -> String {
    let params: Vec<String> = c
        .params()
        .iter()
        .map(|a| {
            let kind = c
                .nodes()
                .get(a.node)
                .and_then(|n| match n {
                    BlueprintNode::Primitive(f) => f.params().get(a.slot).map(|p| kind_str(p.kind)),
                    BlueprintNode::Composite(_) => None,
                })
                .unwrap_or("?");
            format!("{}:{}", a.name, kind)
        })
        .collect();
    let outs: Vec<String> = c.output().iter().map(|of| of.name.clone()).collect();
    format!("{}({}) -> ({})", c.name(), params.join(", "), outs.join(", "))
}

/// The unified leaf-label both views render through (#48): `factory.label()`
/// enriched in three value-empty ways (names, never values — C22 "structure
/// before"), folded into one `factory.label(...)` form:
///
/// 1. A `<field> → ` consumer-side prefix per input slot fed by a **multi-output
///    producer** (the headline — macd's `histogram` driving `Exposure`). Single-output
///    producers contribute nothing, so single-out graphs (sample sma_cross interior
///    and main graph) stay prefix-free. Drawn outside the `(...)`, like the
///    `output_binding` consumer-prefix form, because ascii-dag 0.9.1 silently drops
///    an edge label it cannot place.
/// 2. The leaf's param **names** in `(...)`. The source is [`ParamNames`]: the
///    composite path keeps using the alias overlay filtered to this node (so `where:`
///    stays byte-identical — only aliased slots, never factory defaults); the
///    blueprint-root path uses the factory's declared names.
/// 3. The leaf's input-slot stubs (`#Sf`, …) when it is a multi-input fan-in. The
///    `stub_ctx` is the borrowed composite (root or interior) the wired slots
///    resolve against; both views thread it, so a top-level fan-in stubs exactly as
///    an interior one does — one shared path, no root carve-out (#49).
///
/// Params and stubs are `; `-separated inside the `(...)` when both present; the
/// field prefix always sits outside the parens. The bare label results when none of
/// the three enrichments apply.
fn leaf_label(
    nodes: &[BlueprintNode],
    edges: &[Edge],
    entries: &[Entry],
    index: usize,
    factory: &PrimitiveBuilder,
    param_names: &ParamNames,
    stub_ctx: &Composite,
) -> String {
    let params: Vec<&str> = match param_names {
        ParamNames::Aliases(aliases) => {
            aliases.iter().filter(|a| a.node == index).map(|a| a.name.as_str()).collect()
        }
        ParamNames::Factory => factory.params().iter().map(|p| p.name.as_str()).collect(),
    };

    // wired input slots: the distinct `.slot` values targeting this node across
    // interior/root edges and external entries (roles or sources).
    let mut slots: Vec<usize> = Vec::new();
    for e in edges {
        if e.to == index && !slots.contains(&e.slot) {
            slots.push(e.slot);
        }
    }
    for entry in entries {
        for t in entry.targets {
            if t.node == index && !slots.contains(&t.slot) {
                slots.push(t.slot);
            }
        }
    }
    slots.sort_unstable();
    let stubs: Vec<String> = if slots.len() > 1 {
        fan_in_identifiers(stub_ctx, index, &slots)
    } else {
        Vec::new()
    };

    let inner: String = match (params.is_empty(), stubs.is_empty()) {
        (true, true) => factory.label(),
        (false, true) => format!("{}({})", factory.label(), params.join(", ")),
        (true, false) => format!("{}({})", factory.label(), stubs.join(",")),
        (false, false) => {
            format!("{}({}; {})", factory.label(), params.join(", "), stubs.join(","))
        }
    };

    // field prefixes: for each edge feeding this leaf from a multi-output producer,
    // a `<field> → ` consumer-side prefix, in slot order for determinism. A no-op for
    // both current corpora's single-output interiors (so `where:` is byte-stable).
    let mut fed: Vec<(usize, String)> = Vec::new();
    for e in edges {
        if e.to != index {
            continue;
        }
        if let Some(field) = multi_output_field_name(nodes, e.from, e.from_field) {
            fed.push((e.slot, field));
        }
    }
    fed.sort_by_key(|(slot, _)| *slot);
    if fed.is_empty() {
        return inner;
    }
    // a per-field `<field> → ` stack, then the (possibly enriched) label.
    let prefix = fed.iter().map(|(_, f)| format!("{f} \u{2192} ")).collect::<String>();
    format!("{prefix}{inner}")
}

/// The driving field's *name* when producer `from` (in `nodes`) is a **multi-output**
/// producer feeding its field `from_field` into a consumer; `None` when single-output
/// (no prefix — keeps single-out graphs clean). Operates on a borrowed node slice, so
/// it serves both views uniformly (blueprint root and composite interior).
///
/// - Composite producer: multi-output iff `output().len() > 1`; the name is
///   `output()[from_field].name` (the headline — macd's `output()[2] == "histogram"`).
/// - Leaf producer: pre-build field names are unavailable (#43), so a leaf's output
///   arity is unknown here. Treat `from_field > 0` as the only structurally-certain
///   multi-output signal and fall back to the field **index** as a string; this case
///   is absent in both current corpora and must never panic.
fn multi_output_field_name(nodes: &[BlueprintNode], from: usize, from_field: usize) -> Option<String> {
    match nodes.get(from)? {
        BlueprintNode::Composite(c) => {
            if c.output().len() > 1 {
                Some(
                    c.output()
                        .get(from_field)
                        .map(|of| of.name.clone())
                        .unwrap_or_else(|| from_field.to_string()),
                )
            } else {
                None
            }
        }
        BlueprintNode::Primitive(_) => (from_field > 0).then(|| from_field.to_string()),
    }
}

/// One `#…` identifier per wired slot of a fan-in leaf, in slot order.
/// - A role-fed slot uses the role name verbatim (`#price`), never shortened.
/// - An interior-fed slot uses its source signature, never shorter than the
///   source's **base** (type initial + alias initials), extended into the
///   recursive tail only as far as needed to be unique among the siblings.
/// - Two siblings with equal full signatures (interchangeable inputs) cannot be
///   separated — those slots fall back to the positional letter `#A`. The engine
///   constraint guarantees no configuration-distinct pair fully collides, so a
///   valid blueprint reaches the fallback only for genuinely-interchangeable
///   inputs.
fn fan_in_identifiers(c: &Composite, index: usize, slots: &[usize]) -> Vec<String> {
    // per slot: (slot, signature, base_len, is_role)
    let srcs: Vec<(usize, String, usize, bool)> = slots
        .iter()
        .map(|&slot| {
            let (sig, base, is_role) = slot_source(c, index, slot);
            (slot, sig, base, is_role)
        })
        .collect();
    srcs.iter()
        .map(|(slot, sig, base, is_role)| {
            if *is_role {
                return format!("#{sig}"); // role name verbatim
            }
            let others: Vec<&String> =
                srcs.iter().filter(|(s, _, _, _)| s != slot).map(|(_, x, _, _)| x).collect();
            match unique_prefix_from(sig, *base, &others) {
                Some(p) => format!("#{p}"),
                None => format!("#{}", (b'A' + *slot as u8) as char), // interchangeable fallback
            }
        })
        .collect()
}

/// The source feeding `(index, slot)`: `(signature, base_len, is_role)`. A role
/// returns its name verbatim with `is_role = true` (base_len unused); an interior
/// producer returns its `signature_of` and its base length (type initial + alias
/// initials).
fn slot_source(c: &Composite, index: usize, slot: usize) -> (String, usize, bool) {
    for e in c.edges() {
        if e.to == index && e.slot == slot {
            let sig = signature_of(c.nodes(), c.edges(), c.input_roles(), c.params(), e.from);
            return (sig, signature_base_len(c, e.from), false);
        }
    }
    for r in c.input_roles() {
        if r.targets.iter().any(|t| t.node == index && t.slot == slot) {
            return (r.name.clone(), 0, true);
        }
    }
    (String::new(), 0, false)
}

/// The base length of an interior node's signature: 1 (type / composite-name
/// initial) plus one per declared param alias on that node — the minimum the
/// rendered identifier never goes below.
fn signature_base_len(c: &Composite, node: usize) -> usize {
    match &c.nodes()[node] {
        BlueprintNode::Primitive(_) => 1 + aliases_on(c.params(), node).count(),
        BlueprintNode::Composite(_) => 1,
    }
}

/// The shortest prefix of `sig` of length ≥ `base` that no `other` starts with —
/// i.e. distinguishes `sig` from all siblings while never dropping below the
/// base. `None` when some `other` equals `sig` in full (inseparable —
/// interchangeable, caller uses the positional fallback).
fn unique_prefix_from(sig: &str, base: usize, others: &[&String]) -> Option<String> {
    if others.iter().any(|o| o.as_str() == sig) {
        return None;
    }
    let chars: Vec<char> = sig.chars().collect();
    if chars.is_empty() {
        return Some(String::new()); // degenerate (no producer); not reached for a wired slot
    }
    let start = base.max(1).min(chars.len());
    for len in start..=chars.len() {
        let prefix: String = chars[..len].iter().collect();
        if others.iter().all(|o| !o.starts_with(&prefix)) {
            return Some(prefix);
        }
    }
    Some(sig.to_string())
}

/// Render one composite's interior as a flat graph: interior leaves as
/// `[type(param…; #slot…)]` (aliased param names + ordered input-slot stubs folded
/// in via `leaf_label`), nested composites as opaque `[name]`, and an `[<name>]`
/// entry marker per input role (wired to its interior targets). A re-exported
/// output is **not** a standalone node: its name is folded onto its producing
/// node's label as a binding (`[macd := Sub(…)]`, tuple `(a, b) := …` for several
/// outputs on one node) via [`output_binding`] — so the drawn graph is exactly the
/// computation DAG, every node a real step (C23: the name is a render symbol on the
/// producer, never a wired terminal). The title line is the composite's typed
/// `signature` (`name(p:kind, …) -> (out, …)`); params live in the signature, not
/// as marker nodes.
fn render_definition(c: &Composite, color: Color) -> String {
    // the same shared graph core the main graph uses (#48); the composite-specific
    // borders: param names from the alias overlay, entries from input roles, the
    // output record folded as bindings, fan-in stub context available, and the typed
    // signature as title.
    let entries: Vec<Entry> = c
        .input_roles()
        .iter()
        .map(|role| Entry { name: role.name.clone(), targets: &role.targets })
        .collect();
    let title = signature(c);
    render_graph(
        c.nodes(),
        c.edges(),
        &entries,
        c.output(),
        ParamNames::Aliases(c.params()),
        c,
        Some(&title),
        color,
    )
}

/// The `name := ` (single) or `(n1, n2) := ` (tuple) binding prefix for interior
/// node `i`, if any `OutField` re-exports it; `None` for a non-output node. Names
/// are ordered by re-exported `field` index (ties keep author order). The producer
/// label follows the prefix; no standalone output node or producer→output edge is
/// emitted (the output *is* the producer, surfaced by name — C23).
fn output_binding(output: &[OutField], i: usize) -> Option<String> {
    let mut outs: Vec<&OutField> = output.iter().filter(|of| of.node == i).collect();
    if outs.is_empty() {
        return None;
    }
    outs.sort_by_key(|of| of.field);
    let names: Vec<&str> = outs.iter().map(|of| of.name.as_str()).collect();
    Some(match names.as_slice() {
        [one] => format!("{one} := "),
        many => format!("({}) := ", many.join(", ")),
    })
}

/// Compiled view: the flat post-inline graph (no clusters; boundaries dissolved,
/// C23). Each `Box<dyn Node>` labels itself; node display id = node index.
pub fn render_compilat(
    nodes: &[Box<dyn Node>],
    sources: &[SourceSpec],
    edges: &[Edge],
    color: Color,
) -> String {
    let mut labels: Vec<String> = nodes.iter().map(|n| n.label()).collect();
    let source_base = labels.len();
    for src in sources {
        labels.push(format!("source:{:?}", src.kind));
    }

    let mut edge_pairs: Vec<(usize, usize)> = edges.iter().map(|e| (e.from, e.to)).collect();
    for (i, src) in sources.iter().enumerate() {
        for t in &src.targets {
            edge_pairs.push((source_base + i, t.node));
        }
    }
    render_flat(&labels, &edge_pairs, color)
}