//! Standard transform definitions
//!
//! This module provides pre-built transforms for common use cases.
//! All transforms are defined as static references using `once_cell::sync::Lazy`.

use crate::lex::assembling::{AttachAnnotations, AttachRoot};
use crate::lex::parsing::ir::ParseNode;
use crate::lex::parsing::Document;
use crate::lex::token::Token;
use crate::lex::transforms::stages::{
    CoreTokenization, ParseInlines, Parsing, SemanticIndentation,
};
use crate::lex::transforms::{Runnable, Transform};
use once_cell::sync::Lazy;
use std::ops::Range;

/// Type alias for token stream (to satisfy clippy::type_complexity)
pub type TokenStream = Vec<(Token, Range<usize>)>;

/// Type alias for lexing transform
pub type LexingTransform = Transform<String, TokenStream>;

/// Type alias for AST transform
pub type AstTransform = Transform<String, Document>;

/// Core tokenization transform: String → Vec<(Token, Range<usize>)>
///
/// Converts source text into a flat token stream using the logos lexer.
/// This is the first stage of any lex pipeline.
///
/// # Example
///
/// ```rust
/// use lex_parser::lex::transforms::standard::CORE_TOKENIZATION;
///
/// let tokens = CORE_TOKENIZATION.run("Hello world\n".to_string()).unwrap();
/// assert!(!tokens.is_empty());
/// ```
pub static CORE_TOKENIZATION: Lazy<LexingTransform> =
    Lazy::new(|| Transform::from_fn(Ok).then(CoreTokenization::new()));

/// Lexing transform: String → Vec<(Token, Range<usize>)>
///
/// Complete lexical analysis including:
/// 1. Core tokenization (logos)
/// 2. Semantic indentation (Indent/Dedent)
///
/// This produces a fully-processed token stream ready for parsing.
///
/// # Example
///
/// ```rust
/// use lex_parser::lex::transforms::standard::LEXING;
///
/// let tokens = LEXING.run("Session:\n    Content\n".to_string()).unwrap();
/// // tokens now include Indent/Dedent
/// ```
pub static LEXING: Lazy<LexingTransform> = Lazy::new(|| {
    Transform::from_fn(Ok)
        .then(CoreTokenization::new())
        .then(SemanticIndentation::new())
});

/// Type alias for IR transform
pub type IrTransform = Transform<String, ParseNode>;

/// String to IR transform: String → ParseNode
///
/// Pipeline from source text to intermediate representation (IR):
/// 1. Core tokenization
/// 2. Semantic indentation
/// 3. Line token grouping
/// 4. Parsing to IR
///
/// # Example
///
/// ```rust
/// use lex_parser::lex::transforms::standard::TO_IR;
///
/// let ir = TO_IR.run("Hello world\n".to_string()).unwrap();
/// ```
pub static TO_IR: Lazy<IrTransform> = Lazy::new(|| Transform::from_fn(Ok).then(Parsing::new()));

/// String to AST transform: String → Document
///
/// Complete pipeline from source text to parsed AST:
/// 1. Core tokenization
/// 2. Semantic indentation
/// 3. Line token grouping
/// 4. Parsing to IR
/// 5. Building AST root session
/// 6. Attaching root session to Document
/// 7. Attaching annotations as metadata
///
/// This is the standard transform for most use cases.
///
/// # Example
///
/// ```rust
/// use lex_parser::lex::transforms::standard::STRING_TO_AST;
///
/// let doc = STRING_TO_AST.run("Hello world\n".to_string()).unwrap();
/// assert!(!doc.root.children.is_empty());
/// ```
pub static STRING_TO_AST: Lazy<AstTransform> = Lazy::new(|| {
    Transform::from_fn(|s: String| {
        run_string_to_ast(
            s,
            crate::lex::assembling::stages::normalize_labels::Mode::Strict,
        )
    })
});

/// Shared source→`Document` front-end, **before** annotation attachment.
///
/// This is the single, canonical parser front-end. It owns every stage
/// from raw source to an [`AttachRoot`]-assembled [`Document`] whose
/// labelled annotations are still standalone children (annotation
/// *attachment* — folding them into metadata — happens downstream).
///
/// Both entry points share this:
/// - [`run_string_to_ast`] (the standard / LSP pipeline) calls it, then
///   attaches annotations, normalizes labels, applies table config, and
///   copies the prepass results onto the document.
/// - the include resolver ([`crate::lex::includes::resolve_from_source`])
///   calls it, then splices included subtrees into the still-detached
///   children, defers attachment until after the splice, and uses
///   permissive label mode.
///
/// Keeping both behind one function is the whole point of de-duplication
/// (lex#722): the reference-line pre-pass — and any future front-end
/// stage — lives in exactly one place and can never drift between the
/// direct-parse path and the include-resolver path again.
///
/// Returns the assembled (pre-attachment) [`Document`] together with the
/// [`AnchoringPrepass`](crate::lex::anchoring::AnchoringPrepass) so the
/// caller can copy `reference_lines` / `diagnostics` onto the final
/// document at whatever point in its tail suits it.
pub(crate) fn parse_to_attached_root(
    s: String,
) -> Result<
    (
        crate::lex::ast::Document,
        crate::lex::anchoring::AnchoringPrepass,
    ),
    crate::lex::transforms::TransformError,
> {
    // Ensure source ends with newline (required for parsing)
    let source = if !s.is_empty() && !s.ends_with('\n') {
        format!("{s}\n")
    } else {
        s
    };

    // Reference-line pre-pass (§2.3): identify whole-element-anchoring reference
    // lines so their tokens can be removed from the stream *before* structural
    // parsing — the surrounding lines then keep their original adjacency (a
    // reference line must not be mistaken for the blank line that separates a
    // definition from a session). See `crate::lex::anchoring`.
    //
    // Critically, we do *not* edit the source string. We tokenize the ORIGINAL
    // source (so every token keeps its original byte range), drop the tokens
    // belonging to each reference line — including each line's terminating
    // newline, so the lines above and below become directly adjacent — and then
    // run semantic indentation and parse against the original source. The result
    // is that every AST node range stays in original-source coordinates, even
    // for elements that appear *after* a reference line. (Editing the source
    // string instead would shift every downstream offset into a "cleaned-source"
    // coordinate system that no longer matches what the editor holds.)
    let prepass = crate::lex::anchoring::extract_reference_lines(&source);

    // Core tokenization on the original source (flat tokens, original ranges),
    // then drop the reference-line tokens, then semantic indentation.
    let core_tokens = CoreTokenization::new().run(source.clone())?;
    let core_tokens = prepass.filter_tokens(core_tokens);
    let tokens = SemanticIndentation::new().run(core_tokens)?;

    // Parse to AST against the original source (keeps location tracking in
    // original-source coordinates). Group the flat tokens into lines before
    // handing them to the main grouped-stream entry point.
    let mut mapper = crate::lex::lexing::transformations::LineTokenGroupingMapper::new();
    let grouped_tokens = mapper.map(tokens);
    let mut output =
        crate::lex::parsing::engine::parse_from_grouped_stream(grouped_tokens, &source).map_err(
            |e| crate::lex::transforms::TransformError::StageFailed {
                stage: "Parser".to_string(),
                message: e.to_string(),
            },
        )?;

    // Parse inline elements in root session before assembly
    output.root = ParseInlines::new().run(output.root)?;

    // Parse inlines in document title if present
    if let Some(ref mut title) = output.title {
        title.content.ensure_inline_parsed_with_anchors();
    }

    // Attach root session and title to a document (annotations stay as
    // standalone children — the caller decides when to attach them).
    let doc = AttachRoot::new().run(output)?;

    Ok((doc, prepass))
}

/// Run the full source→AST pipeline with a chosen
/// [`NormalizeLabels`](crate::lex::assembling::stages::NormalizeLabels)
/// mode. The standard pipeline ([`STRING_TO_AST`]) is the strict-mode
/// instantiation of this; the LSP's permissive parse path
/// ([`crate::lex::parsing::parse_document_permissive`]) is the
/// permissive-mode instantiation.
///
/// Keeping both modes routed through a single pipeline function
/// avoids the maintenance hazard of forking the lexing / parsing /
/// assembling sequence — adding a new stage or reordering existing
/// ones only needs to happen here.
pub fn run_string_to_ast(
    s: String,
    label_mode: crate::lex::assembling::stages::normalize_labels::Mode,
) -> Result<crate::lex::ast::Document, crate::lex::transforms::TransformError> {
    use crate::lex::assembling::stages::normalize_labels::Mode;

    // Shared front-end: source → assembled Document (annotations still
    // standalone) + reference-line pre-pass results.
    let (mut doc, prepass) = parse_to_attached_root(s)?;

    // Attach annotations as metadata
    doc = AttachAnnotations::new().run(doc)?;

    // Normalize labels under the requested mode.
    let normalize = match label_mode {
        Mode::Strict => crate::lex::assembling::stages::NormalizeLabels::new(),
        Mode::Permissive => crate::lex::assembling::stages::NormalizeLabels::permissive(),
    };
    doc = normalize.run(doc)?;

    // Apply table config from :: table :: annotations (header, align)
    doc = crate::lex::assembling::stages::ApplyTableConfig::new().run(doc)?;

    // Attach the reference-line pre-pass results to the document so consumers
    // (babel serializers, LSP documentLink) can read the resolved anchors.
    doc.reference_lines = prepass.reference_lines;
    doc.reference_line_diagnostics = prepass.diagnostics;

    Ok(doc)
}

#[cfg(test)]
mod tests {
    use super::*;
    use crate::lex::token::Token;

    #[test]
    fn test_core_tokenization() {
        let result = CORE_TOKENIZATION.run("Hello world\n".to_string()).unwrap();
        assert!(!result.is_empty());

        // Should have Text tokens
        assert!(result.iter().any(|(t, _)| matches!(t, Token::Text(_))));
    }

    #[test]
    fn test_lexing_adds_indentation() {
        let source = "Session:\n    Content\n".to_string();
        let result = LEXING.run(source).unwrap();

        // Should have Indent and Dedent tokens
        assert!(result.iter().any(|(t, _)| matches!(t, Token::Indent(_))));
        assert!(result.iter().any(|(t, _)| matches!(t, Token::Dedent(_))));
    }

    #[test]
    fn test_lexing_no_indentation() {
        let source = "Hello\n".to_string();
        let result = LEXING.run(source).unwrap();

        // Should not have Indent/Dedent
        assert!(!result.iter().any(|(t, _)| matches!(t, Token::Indent(_))));
        assert!(!result.iter().any(|(t, _)| matches!(t, Token::Dedent(_))));
    }

    #[test]
    fn test_string_to_ast_simple() {
        let result = STRING_TO_AST.run("Hello world\n".to_string()).unwrap();
        assert!(!result.root.children.is_empty());
    }

    #[test]
    fn test_string_to_ast_with_session() {
        let source = "Session:\n    Content here\n".to_string();
        let result = STRING_TO_AST.run(source).unwrap();

        assert!(!result.root.children.is_empty());
    }

    #[test]
    fn test_string_to_ast_adds_newline() {
        // Test that source without trailing newline works
        let result = STRING_TO_AST.run("Hello world".to_string()).unwrap();
        assert!(!result.root.children.is_empty());
    }

    #[test]
    fn test_transforms_are_reusable() {
        // Test that we can use the same transform multiple times
        let result1 = LEXING.run("Hello\n".to_string()).unwrap();
        let result2 = LEXING.run("World\n".to_string()).unwrap();

        assert!(!result1.is_empty());
        assert!(!result2.is_empty());
    }
}
