use crate::atom_table::*;
use crate::codegen::CodeGenSettings;
use crate::forms::*;
use crate::instructions::*;
use crate::machine::disjuncts::*;
use crate::machine::loader::*;
use crate::machine::machine_errors::*;
use crate::parser::ast::*;

use indexmap::IndexSet;

use std::cell::Cell;
use std::convert::TryFrom;

pub(crate) fn to_op_decl(
    prec: u16,
    spec: Atom,
    name: Atom,
) -> Result<OpDecl, CompilationError> {
    match spec {
        atom!("xfx") => Ok(OpDecl::new(OpDesc::build_with(prec, XFX as u8), name)),
        atom!("xfy") => Ok(OpDecl::new(OpDesc::build_with(prec, XFY as u8), name)),
        atom!("yfx") => Ok(OpDecl::new(OpDesc::build_with(prec, YFX as u8), name)),
        atom!("fx") => Ok(OpDecl::new(OpDesc::build_with(prec, FX as u8), name)),
        atom!("fy") => Ok(OpDecl::new(OpDesc::build_with(prec, FY as u8), name)),
        atom!("xf") => Ok(OpDecl::new(OpDesc::build_with(prec, XF as u8), name)),
        atom!("yf") => Ok(OpDecl::new(OpDesc::build_with(prec, YF as u8), name)),
        _ => Err(CompilationError::InconsistentEntry),
    }
}

fn setup_op_decl(
    mut terms: Vec<Term>,
    atom_tbl: &mut AtomTable,
) -> Result<OpDecl, CompilationError> {
    let name = match terms.pop().unwrap() {
        Term::Literal(_, Literal::Atom(name)) => name,
        Term::Literal(_, Literal::Char(c)) => atom_tbl.build_with(&c.to_string()),
        _ => return Err(CompilationError::InconsistentEntry),
    };

    let spec = match terms.pop().unwrap() {
        Term::Literal(_, Literal::Atom(name)) => name,
        Term::Literal(_, Literal::Char(c)) => atom_tbl.build_with(&c.to_string()),
        _ => return Err(CompilationError::InconsistentEntry),
    };

    let prec = match terms.pop().unwrap() {
        Term::Literal(_, Literal::Fixnum(bi)) => match u16::try_from(bi.get_num()) {
            Ok(n) if n <= 1200 => n,
            _ => return Err(CompilationError::InconsistentEntry),
        },
        _ => return Err(CompilationError::InconsistentEntry),
    };

    to_op_decl(prec, spec, name)
}

fn setup_predicate_indicator(term: &mut Term) -> Result<PredicateKey, CompilationError> {
    match term {
        Term::Clause(_, slash, ref mut terms)
            if (*slash == atom!("/") || *slash == atom!("//")) && terms.len() == 2 =>
        {
            let arity = terms.pop().unwrap();
            let name = terms.pop().unwrap();

            let arity = match arity {
                Term::Literal(_, Literal::Integer(n)) => n.to_usize(),
                Term::Literal(_, Literal::Fixnum(n)) => usize::try_from(n.get_num()).ok(),
                _ => None,
            }.ok_or(CompilationError::InvalidModuleExport)?;

            let name = match name {
                Term::Literal(_, Literal::Atom(name)) => Some(name),
                _ => None,
            }.ok_or(CompilationError::InvalidModuleExport)?;

            if *slash == atom!("/") {
                Ok((name, arity))
            } else {
                Ok((name, arity + 2))
            }
        }
        _ => Err(CompilationError::InvalidModuleExport),
    }
}

fn setup_module_export(
    mut term: Term,
    atom_tbl: &mut AtomTable,
) -> Result<ModuleExport, CompilationError> {
    setup_predicate_indicator(&mut term)
        .map(ModuleExport::PredicateKey)
        .or_else(|_| {
            if let Term::Clause(_, name, terms) = term {
                if terms.len() == 3 && name == atom!("op") {
                    Ok(ModuleExport::OpDecl(setup_op_decl(terms, atom_tbl)?))
                } else {
                    Err(CompilationError::InvalidModuleDecl)
                }
            } else {
                Err(CompilationError::InvalidModuleDecl)
            }
        })
}

pub(crate) fn build_rule_body(vars: &[Term], body_term: Term) -> Term {
    let head_term = Term::Clause(Cell::default(), atom!(""), vars.iter().cloned().collect());
    let rule = vec![head_term, body_term];

    Term::Clause(Cell::default(), atom!(":-"), rule)
}

pub(super) fn setup_module_export_list(
    mut export_list: Term,
    atom_tbl: &mut AtomTable,
) -> Result<Vec<ModuleExport>, CompilationError> {
    let mut exports = vec![];

    while let Term::Cons(_, t1, t2) = export_list {
        let module_export = setup_module_export(*t1, atom_tbl)?;

        exports.push(module_export);
        export_list = *t2;
    }

    if let Term::Literal(_, Literal::Atom(atom!("[]"))) = export_list {
        Ok(exports)
    } else {
        Err(CompilationError::InvalidModuleDecl)
    }
}

fn setup_module_decl(
    mut terms: Vec<Term>,
    atom_tbl: &mut AtomTable,
) -> Result<ModuleDecl, CompilationError> {
    let export_list = terms.pop().unwrap();
    let name = terms.pop().unwrap();

    let name = match name {
        Term::Literal(_, Literal::Atom(name)) => Some(name),
        _ => None,
    }.ok_or(CompilationError::InvalidModuleDecl)?;

    let exports = setup_module_export_list(export_list, atom_tbl)?;

    Ok(ModuleDecl { name, exports })
}

fn setup_use_module_decl(mut terms: Vec<Term>) -> Result<ModuleSource, CompilationError> {
    match terms.pop().unwrap() {
        Term::Clause(_, name, mut terms)
            if name == atom!("library") && terms.len() == 1 =>
        {
            match terms.pop().unwrap() {
                Term::Literal(_, Literal::Atom(name)) => Ok(ModuleSource::Library(name)),
                _ => Err(CompilationError::InvalidModuleDecl),
            }
        }
        Term::Literal(_, Literal::Atom(name)) => Ok(ModuleSource::File(name)),
        _ => Err(CompilationError::InvalidUseModuleDecl),
    }
}

type UseModuleExport = (ModuleSource, IndexSet<ModuleExport>);

fn setup_qualified_import(
    mut terms: Vec<Term>,
    atom_tbl: &mut AtomTable,
) -> Result<UseModuleExport, CompilationError> {
    let mut export_list = terms.pop().unwrap();
    let module_src = match terms.pop().unwrap() {
        Term::Clause(_, name, mut terms)
            if name == atom!("library") && terms.len() == 1 =>
        {
            match terms.pop().unwrap() {
                Term::Literal(_, Literal::Atom(name)) => Ok(ModuleSource::Library(name)),
                _ => Err(CompilationError::InvalidModuleDecl),
            }
        }
        Term::Literal(_, Literal::Atom(name)) => Ok(ModuleSource::File(name)),
        _ => Err(CompilationError::InvalidUseModuleDecl),
    }?;

    let mut exports = IndexSet::new();

    while let Term::Cons(_, t1, t2) = export_list {
        exports.insert(setup_module_export(*t1, atom_tbl)?);
        export_list = *t2;
    }

    if let Term::Literal(_, Literal::Atom(atom!("[]"))) = export_list {
        Ok((module_src, exports))
    } else {
        Err(CompilationError::InvalidModuleDecl)
    }
}

/*
 * setup_meta_predicate tries to extract meta-predicate information
 * from an appropriately formed declaration
 *
 * :- meta_predicate maplist(:, ?, ?).
 *
 * indicating that, for each QueryTerm call to maplist/3, the first
 * argument is to be expanded with the call resolution ((:)/2)
 * operator, the first argument of which is the name of the host
 * module, as an atom. For example,
 *
 * p(X) :- maplist(X, [a,b,c], Result).
 *
 * If p/2 is defined in a module named "mod", the call is expanded to
 *
 * maplist(mod:X, [a,b,c], Result).
 *
 * before the predicate is compiled to WAM instructions.
 *
 * If the term bound to X -- the predicate to be called -- is
 * qualified with (:)/2 already, the innermost qualifier is used for
 * call resolution.
 *
 * The three arguments returned by a successful call are the module name,
 * predicate name, and the list of meta-specs, one for each predicate argument.
 *
 * The module name might be used to specify intra-module meta-predicates whose
 * module is not yet defined. There are several examples of this
 * contained in src/lib/ops_and_meta_predicates.pl, which is loaded before
 * src/lib/builtins.pl.
 *
 * Meta-specs have three forms:
 *
 * (:)  (the argument should be expanded with (:)/2 as described above)
 * +    (mode declarations under the mode syntax, which currently have no effect)
 * -
 * ?
 */

fn setup_meta_predicate<'a, LS: LoadState<'a>>(
    mut terms: Vec<Term>,
    loader: &mut Loader<'a, LS>,
) -> Result<(Atom, Atom, Vec<MetaSpec>), CompilationError> {
    fn get_name_and_meta_specs(
        name: Atom,
        terms: &mut [Term],
    ) -> Result<(Atom, Vec<MetaSpec>), CompilationError> {
        let mut meta_specs = vec![];

        for meta_spec in terms.into_iter() {
            match meta_spec {
                Term::Literal(_, Literal::Atom(meta_spec)) => {
                    let meta_spec = match meta_spec {
                        atom!("+") => MetaSpec::Plus,
                        atom!("-") => MetaSpec::Minus,
                        atom!("?") => MetaSpec::Either,
                        atom!(":") => MetaSpec::Colon,
                        _ => return Err(CompilationError::InvalidMetaPredicateDecl),
                    };

                    meta_specs.push(meta_spec);
                }
                Term::Literal(_, Literal::Fixnum(n)) => match usize::try_from(n.get_num()) {
                    Ok(n) if n <= MAX_ARITY => {
                        meta_specs.push(MetaSpec::RequiresExpansionWithArgument(n));
                    }
                    _ => {
                        return Err(CompilationError::InvalidMetaPredicateDecl);
                    }
                },
                _ => {
                    return Err(CompilationError::InvalidMetaPredicateDecl);
                }
            }
        }

        Ok((name, meta_specs))
    }

    match terms.pop().unwrap() {
        Term::Clause(_, name, mut terms) if name == atom!(":") && terms.len() == 2 => {
            let spec = terms.pop().unwrap();
            let module_name = terms.pop().unwrap();

            match module_name {
                Term::Literal(_, Literal::Atom(module_name)) => match spec {
                    Term::Clause(_, name, mut terms) => {
                        let (name, meta_specs) = get_name_and_meta_specs(name, &mut terms)?;
                        Ok((module_name, name, meta_specs))
                    }
                    _ => Err(CompilationError::InvalidMetaPredicateDecl),
                },
                _ => Err(CompilationError::InvalidMetaPredicateDecl),
            }
        }
        Term::Clause(_, name, mut terms) => {
            let (name, meta_specs) = get_name_and_meta_specs(name, &mut terms)?;
            Ok((
                loader.payload.compilation_target.module_name(),
                name,
                meta_specs,
            ))
        }
        _ => Err(CompilationError::InvalidMetaPredicateDecl),
    }
}

pub(super) fn setup_declaration<'a, LS: LoadState<'a>>(
    loader: &mut Loader<'a, LS>,
    mut terms: Vec<Term>,
) -> Result<Declaration, CompilationError> {
    let term = terms.pop().unwrap();

    match term {
        Term::Clause(_, name, mut terms) => match (name, terms.len()) {
            (atom!("dynamic"), 1) => {
                let (name, arity) = setup_predicate_indicator(&mut terms.pop().unwrap())?;
                Ok(Declaration::Dynamic(name, arity))
            }
            (atom!("module"), 2) => {
                let atom_tbl = &mut LS::machine_st(&mut loader.payload).atom_tbl;
                Ok(Declaration::Module(setup_module_decl(terms, atom_tbl)?))
            }
            (atom!("op"), 3) => {
                let atom_tbl = &mut LS::machine_st(&mut loader.payload).atom_tbl;
                Ok(Declaration::Op(setup_op_decl(terms, atom_tbl)?))
            }
            (atom!("non_counted_backtracking"), 1) => {
                let (name, arity) = setup_predicate_indicator(&mut terms.pop().unwrap())?;
                Ok(Declaration::NonCountedBacktracking(name, arity))
            }
            (atom!("use_module"), 1) => Ok(Declaration::UseModule(setup_use_module_decl(terms)?)),
            (atom!("use_module"), 2) => {
                let atom_tbl = &mut LS::machine_st(&mut loader.payload).atom_tbl;
                let (name, exports) = setup_qualified_import(terms, atom_tbl)?;

                Ok(Declaration::UseQualifiedModule(name, exports))
            }
            (atom!("meta_predicate"), 1) => {
                let (module_name, name, meta_specs) = setup_meta_predicate(terms, loader)?;
                Ok(Declaration::MetaPredicate(module_name, name, meta_specs))
            }
            _ => Err(CompilationError::InconsistentEntry),
        },
        _ => Err(CompilationError::InconsistentEntry),
    }
}

fn build_meta_predicate_clause<'a, LS: LoadState<'a>>(
    loader: &mut Loader<'a, LS>,
    module_name: Atom,
    terms: Vec<Term>,
    meta_specs: Vec<MetaSpec>,
) -> Vec<Term> {
    let mut arg_terms = Vec::with_capacity(terms.len());

    for (term, meta_spec) in terms.into_iter().zip(meta_specs.iter()) {
        if let MetaSpec::RequiresExpansionWithArgument(supp_args) = meta_spec {
            if let Some(name) = term.name() {
                if name == atom!("$call") {
                    arg_terms.push(term);
                    continue;
                }

                let arity = term.arity();

                fn get_qualified_name(
                    module_term: &Term,
                    qualified_term: &Term,
                ) -> Option<(Atom, Atom)> {
                    if let Term::Literal(_, Literal::Atom(module_name)) = module_term {
                        if let Some(name) = qualified_term.name() {
                            return Some((*module_name, name));
                        }
                    }

                    None
                }

                fn identity_fn(_module_name: Atom, term: Term) -> Term {
                    term
                }

                fn tag_with_module_name(module_name: Atom, term: Term) -> Term {
                    Term::Clause(Cell::default(), atom!(":"), vec![
                        Term::Literal(Cell::default(), Literal::Atom(module_name)),
                        term
                    ])
                }

                let process_term: fn(Atom, Term) -> Term;

                let (module_name, key, term) = match term {
                    Term::Clause(cell, atom!(":"), mut terms) if terms.len() == 2 => {
                        if let Some((module_name, name)) = get_qualified_name(&terms[0], &terms[1]) {
                            process_term = tag_with_module_name;
                            (module_name, (name, terms[1].arity() + supp_args), terms.pop().unwrap())
                        } else {
                            arg_terms.push(Term::Clause(cell, atom!(":"), terms));
                            continue;
                        }
                    }
                    term => {
                        process_term = identity_fn;
                        (module_name, (name, arity + supp_args), term)
                    }
                };

                let term = match term {
                    Term::Clause(cell, name, mut terms) => {
                        if let Some(Term::Literal(_, Literal::CodeIndex(_))) = terms.last() {
                            arg_terms.push(process_term(
                                module_name,
                                Term::Clause(cell, name, terms),
                            ));

                            continue;
                        }

                        let idx = loader.get_or_insert_qualified_code_index(module_name, key);

                        terms.push(Term::Literal(Cell::default(), Literal::CodeIndex(idx)));
                        process_term(module_name, Term::Clause(cell, name, terms))
                    }
                    Term::Literal(cell, Literal::Atom(name)) => {
                        let idx = loader.get_or_insert_qualified_code_index(module_name, key);

                        process_term(module_name, Term::Clause(
                            cell,
                            name,
                            vec![Term::Literal(Cell::default(), Literal::CodeIndex(idx))],
                        ))
                    }
                    term => term,
                };

                arg_terms.push(term);
                continue;
            }
        }

        arg_terms.push(term);
    }

    arg_terms
}

#[inline]
pub(super) fn clause_to_query_term<'a, LS: LoadState<'a>>(
    loader: &mut Loader<'a, LS>,
    name: Atom,
    mut terms: Vec<Term>,
    call_policy: CallPolicy,
) -> QueryTerm {
    if let Some(Term::Literal(_, Literal::CodeIndex(_))) = terms.last() {
        // supplementary code vector indices are unnecessary for
        // root-level clauses.
        terms.pop();
    }

    let mut ct = loader.get_clause_type(name, terms.len());

    if let ClauseType::Named(arity, name, idx) = ct {
        if let Some(meta_specs) = loader.get_meta_specs(name, arity).cloned() {
            let module_name = loader.payload.compilation_target.module_name();
            let terms = build_meta_predicate_clause(
                loader,
                module_name,
                terms,
                meta_specs,
            );

            return QueryTerm::Clause(
                Cell::default(),
                ClauseType::Named(arity, name, idx),
                terms,
                call_policy,
            );
        }

        ct = ClauseType::Named(arity, name, idx);
    }

    QueryTerm::Clause(Cell::default(), ct, terms, call_policy)
}

#[inline]
pub(super) fn qualified_clause_to_query_term<'a, LS: LoadState<'a>>(
    loader: &mut Loader<'a, LS>,
    module_name: Atom,
    name: Atom,
    mut terms: Vec<Term>,
    call_policy: CallPolicy,
) -> QueryTerm {
    if let Some(Term::Literal(_, Literal::CodeIndex(_))) = terms.last() {
        // supplementary code vector indices are unnecessary for
        // root-level clauses.
        terms.pop();
    }

    let mut ct = loader.get_qualified_clause_type(module_name, name, terms.len());

    if let ClauseType::Named(arity, name, idx) = ct {
        if let Some(meta_specs) = loader.get_meta_specs(name, arity).cloned() {
            let terms = build_meta_predicate_clause(
                loader,
                module_name,
                terms,
                meta_specs,
            );

            return QueryTerm::Clause(
                Cell::default(),
                ClauseType::Named(arity, name, idx),
                terms,
                call_policy,
            );
        }

        ct = ClauseType::Named(arity, name, idx);
    }

    QueryTerm::Clause(Cell::default(), ct, terms, call_policy)
}

#[derive(Debug)]
pub(crate) struct Preprocessor {
    settings: CodeGenSettings,
}

impl Preprocessor {
    pub(super) fn new(settings: CodeGenSettings) -> Self {
        Preprocessor {
            settings,
        }
    }

    fn setup_fact(&mut self, term: Term) -> Result<(Fact, VarData), CompilationError> {
        match term {
            Term::Clause(..) | Term::Literal(_, Literal::Atom(..)) => {
                let classifier = VariableClassifier::new(
                    self.settings.default_call_policy(),
                );

                let (head, var_data) = classifier.classify_fact(term)?;
                Ok((Fact { head }, var_data))
            }
            _ => Err(CompilationError::InadmissibleFact),
        }
    }

    fn setup_rule<'a, LS: LoadState<'a>>(
        &mut self,
        loader: &mut Loader<'a, LS>,
        head: Term,
        body: Term,
    ) -> Result<(Rule, VarData), CompilationError> {
        let classifier = VariableClassifier::new(
            self.settings.default_call_policy(),
        );

        let (head, clauses, var_data) = classifier.classify_rule(loader, head, body)?;

        match head {
            Term::Clause(_, name, terms) => Ok((Rule {
                head: (name, terms),
                clauses,
            }, var_data)),
            Term::Literal(_, Literal::Atom(name)) => Ok((Rule {
                head: (name, vec![]),
                clauses,
            }, var_data)),
            _ => Err(CompilationError::InvalidRuleHead),
        }
    }

    /*
    fn try_term_to_query<'a, LS: LoadState<'a>>(
        &mut self,
        loader: &mut Loader<'a, LS>,
        terms: Vec<Term>,
        cut_context: CutContext,
    ) -> Result<TopLevel, CompilationError> {
        Ok(TopLevel::Query(self.setup_query(
            loader,
            terms,
            cut_context,
        )?))
    }
    */

    pub(super) fn try_term_to_tl<'a, LS: LoadState<'a>>(
        &mut self,
        loader: &mut Loader<'a, LS>,
        term: Term,
    ) -> Result<TopLevel, CompilationError> {
        match term {
            Term::Clause(r, name, mut terms) => {
                let is_rule = name == atom!(":-") && terms.len() == 2;

                if is_rule {
                    let tail = terms.pop().unwrap();
                    let head = terms.pop().unwrap();

                    let (rule, var_data) = self.setup_rule(loader, head, tail)?;
                    Ok(TopLevel::Rule(rule, var_data))
                } else {
                    let term = Term::Clause(r, name, terms);
                    let (fact, var_data) = self.setup_fact(term)?;
                    Ok(TopLevel::Fact(fact, var_data))
                }
            }
            term => {
                let (fact, var_data) = self.setup_fact(term)?;
                Ok(TopLevel::Fact(fact, var_data))
            }
        }
    }

    /*
    fn try_terms_to_tls<'a, I: IntoIterator<Item = Term>, LS: LoadState<'a>>(
        &mut self,
        loader: &mut Loader<'a, LS>,
        terms: I,
    ) -> Result<VecDeque<TopLevel>, CompilationError> {
        let mut results = VecDeque::new();

        for term in terms.into_iter() {
            results.push_back(self.try_term_to_tl(loader, term)?);
        }

        Ok(results)
    }
    */
}
