// Functions for storing and retrieving function information. These functions also take care of
// autoloading functions in the $fish_function_path. Actual function evaluation is taken care of by
// the parser and to some degree the builtin handling library.
//
#include "config.h"  // IWYU pragma: keep

// IWYU pragma: no_include <type_traits>
#include <dirent.h>
#include <pthread.h>
#include <stddef.h>

#include <algorithm>
#include <cwchar>
#include <map>
#include <memory>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>

#include "autoload.h"
#include "common.h"
#include "env.h"
#include "event.h"
#include "exec.h"
#include "fallback.h"  // IWYU pragma: keep
#include "function.h"
#include "intern.h"
#include "parser.h"
#include "parser_keywords.h"
#include "reader.h"
#include "wutil.h"  // IWYU pragma: keep

class function_info_t {
   public:
    /// Immutable properties of the function.
    function_properties_ref_t props;
    /// Function description. This may be changed after the function is created.
    wcstring description;
    /// File where this function was defined (intern'd string).
    const wchar_t *const definition_file;
    /// Flag for specifying that this function was automatically loaded.
    const bool is_autoload;

    function_info_t(function_properties_ref_t props, wcstring desc, const wchar_t *def_file,
                    bool autoload);
};

/// Type wrapping up the set of all functions.
/// There's only one of these; it's managed by a lock.
struct function_set_t {
    /// The map of all functions by name.
    std::unordered_map<wcstring, function_info_t> funcs;

    /// Tombstones for functions that should no longer be autoloaded.
    std::unordered_set<wcstring> autoload_tombstones;

    /// The autoloader for our functions.
    autoload_t autoloader{L"fish_function_path"};

    /// Remove a function.
    /// \return true if successful, false if it doesn't exist.
    bool remove(const wcstring &name);

    /// Get the info for a function, or nullptr if none.
    const function_info_t *get_info(const wcstring &name) const {
        auto iter = funcs.find(name);
        return iter == funcs.end() ? nullptr : &iter->second;
    }

    /// \return true if we should allow autoloading a given function.
    bool allow_autoload(const wcstring &name) const;

    function_set_t() = default;
};

/// The big set of all functions.
static owning_lock<function_set_t> function_set;

bool function_set_t::allow_autoload(const wcstring &name) const {
    // Prohibit autoloading if we have a non-autoload (explicit) function, or if the function is
    // tombstoned.
    const auto *info = get_info(name);
    bool has_explicit_func = info && !info->is_autoload;
    bool is_tombstoned = autoload_tombstones.count(name) > 0;
    return !has_explicit_func && !is_tombstoned;
}

/// Make sure that if the specified function is a dynamically loaded function, it has been fully
/// loaded.
/// Note this executes fish script code.
static void try_autoload(const wcstring &name, parser_t &parser) {
    ASSERT_IS_MAIN_THREAD();
    maybe_t<wcstring> path_to_autoload;
    // Note we can't autoload while holding the funcset lock.
    // Lock around a local region.
    {
        auto funcset = function_set.acquire();
        if (funcset->allow_autoload(name)) {
            path_to_autoload = funcset->autoloader.resolve_command(name, env_stack_t::globals());
        }
    }

    // Release the lock and perform any autoload, then reacquire the lock and clean up.
    if (path_to_autoload) {
        // Crucially, the lock is acquired *after* do_autoload_file_at_path().
        autoload_t::perform_autoload(*path_to_autoload, parser);
        function_set.acquire()->autoloader.mark_autoload_finished(name);
    }
}

/// Insert a list of all dynamically loaded functions into the specified list.
static void autoload_names(std::unordered_set<wcstring> &names, int get_hidden) {
    size_t i;

    // TODO: justfy this.
    auto &vars = env_stack_t::principal();
    const auto path_var = vars.get(L"fish_function_path");
    if (path_var.missing_or_empty()) return;

    wcstring_list_t path_list;
    path_var->to_list(path_list);

    for (i = 0; i < path_list.size(); i++) {
        const wcstring &ndir_str = path_list.at(i);
        dir_t dir(ndir_str);
        if (!dir.valid()) continue;

        wcstring name;
        while (dir.read(name)) {
            const wchar_t *fn = name.c_str();
            const wchar_t *suffix;
            if (!get_hidden && fn[0] == L'_') continue;

            suffix = std::wcsrchr(fn, L'.');
            if (suffix && (std::wcscmp(suffix, L".fish") == 0)) {
                wcstring name(fn, suffix - fn);
                names.insert(name);
            }
        }
    }
}

function_info_t::function_info_t(function_properties_ref_t props, wcstring desc,
                                 const wchar_t *def_file, bool autoload)
    : props(std::move(props)),
      description(std::move(desc)),
      definition_file(intern(def_file)),
      is_autoload(autoload) {}

void function_add(wcstring name, wcstring description, function_properties_ref_t props,
                  const wchar_t *filename) {
    ASSERT_IS_MAIN_THREAD();
    auto funcset = function_set.acquire();

    // Historical check. TODO: rationalize this.
    if (name.empty()) {
        return;
    }

    // Remove the old function.
    funcset->remove(name);

    // Check if this is a function that we are autoloading.
    bool is_autoload = funcset->autoloader.autoload_in_progress(name);

    // Create and store a new function.
    auto ins = funcset->funcs.emplace(
        std::move(name),
        function_info_t(std::move(props), std::move(description), filename, is_autoload));
    assert(ins.second && "Function should not already be present in the table");
    (void)ins;
}

std::shared_ptr<const function_properties_t> function_get_properties(const wcstring &name) {
    if (parser_keywords_is_reserved(name)) return nullptr;
    auto funcset = function_set.acquire();
    if (const auto *info = funcset->get_info(name)) {
        return info->props;
    }
    return nullptr;
}

int function_exists(const wcstring &cmd, parser_t &parser) {
    ASSERT_IS_MAIN_THREAD();
    if (parser_keywords_is_reserved(cmd)) return 0;
    try_autoload(cmd, parser);
    auto funcset = function_set.acquire();
    return funcset->funcs.find(cmd) != funcset->funcs.end();
}

void function_load(const wcstring &cmd, parser_t &parser) {
    ASSERT_IS_MAIN_THREAD();
    if (!parser_keywords_is_reserved(cmd)) {
        try_autoload(cmd, parser);
    }
}

int function_exists_no_autoload(const wcstring &cmd) {
    if (parser_keywords_is_reserved(cmd)) return 0;
    auto funcset = function_set.acquire();

    // Check if we either have the function, or it could be autoloaded.
    return funcset->get_info(cmd) || funcset->autoloader.can_autoload(cmd);
}

bool function_set_t::remove(const wcstring &name) {
    size_t amt = funcs.erase(name);
    if (amt > 0) {
        event_remove_function_handlers(name);
    }
    return amt > 0;
}

void function_remove(const wcstring &name) {
    auto funcset = function_set.acquire();
    funcset->remove(name);
    // Prevent (re-)autoloading this function.
    funcset->autoload_tombstones.insert(name);
}

bool function_get_definition(const wcstring &name, wcstring &out_definition) {
    const auto funcset = function_set.acquire();
    const function_info_t *func = funcset->get_info(name);
    if (!func || !func->props) return false;
    // We want to preserve comments that the AST attaches to the header (#5285).
    // Take everything from the end of the header to the end of the body.
    const auto &props = func->props;
    namespace g = grammar;
    tnode_t<g::block_header> header = props->func_node.child<0>();
    tnode_t<g::job_list> jobs = props->func_node.child<1>();
    auto header_src = header.source_range();
    auto jobs_src = jobs.source_range();
    if (header_src && jobs_src) {
        uint32_t body_start = header_src->start + header_src->length;
        uint32_t body_end = jobs_src->start + jobs_src->length;
        assert(body_start <= jobs_src->start && "job list must come after header");
        out_definition = wcstring(props->parsed_source->src, body_start, body_end - body_start);
    }
    return true;
}

bool function_get_desc(const wcstring &name, wcstring &out_desc) {
    const auto funcset = function_set.acquire();
    const function_info_t *func = funcset->get_info(name);
    if (func && !func->description.empty()) {
        out_desc = _(func->description.c_str());
        return true;
    }
    return false;
}

void function_set_desc(const wcstring &name, const wcstring &desc, parser_t &parser) {
    ASSERT_IS_MAIN_THREAD();
    try_autoload(name, parser);
    auto funcset = function_set.acquire();
    auto iter = funcset->funcs.find(name);
    if (iter != funcset->funcs.end()) {
        iter->second.description = desc;
    }
}

bool function_copy(const wcstring &name, const wcstring &new_name) {
    auto funcset = function_set.acquire();
    auto iter = funcset->funcs.find(name);
    if (iter == funcset->funcs.end()) {
        // No such function.
        return false;
    }
    const function_info_t &src_func = iter->second;

    // This new instance of the function shouldn't be tied to the definition file of the
    // original, so pass NULL filename, etc.
    // Note this will NOT overwrite an existing function with the new name.
    // TODO: rationalize if this behavior is desired.
    funcset->funcs.emplace(new_name,
                           function_info_t(src_func.props, src_func.description, nullptr, false));
    return true;
}

wcstring_list_t function_get_names(int get_hidden) {
    std::unordered_set<wcstring> names;
    auto funcset = function_set.acquire();
    autoload_names(names, get_hidden);
    for (const auto &func : funcset->funcs) {
        const wcstring &name = func.first;

        // Maybe skip hidden.
        if (!get_hidden && (name.empty() || name.at(0) == L'_')) {
            continue;
        }
        names.insert(name);
    }
    return wcstring_list_t(names.begin(), names.end());
}

const wchar_t *function_get_definition_file(const wcstring &name) {
    const auto funcset = function_set.acquire();
    const function_info_t *func = funcset->get_info(name);
    return func ? func->definition_file : nullptr;
}

bool function_is_autoloaded(const wcstring &name) {
    const auto funcset = function_set.acquire();
    const function_info_t *func = funcset->get_info(name);
    return func ? func->is_autoload : false;
}

int function_get_definition_lineno(const wcstring &name) {
    const auto funcset = function_set.acquire();
    const function_info_t *func = funcset->get_info(name);
    if (!func) return -1;
    // return one plus the number of newlines at offsets less than the start of our function's
    // statement (which includes the header).
    // TODO: merge with line_offset_of_character_at_offset?
    auto source_range = func->props->func_node.source_range();
    assert(source_range && "Function has no source range");
    uint32_t func_start = source_range->start;
    const wcstring &source = func->props->parsed_source->src;
    assert(func_start <= source.size() && "function start out of bounds");
    return 1 + std::count(source.begin(), source.begin() + func_start, L'\n');
}

void function_invalidate_path() {
    // Remove all autoloaded functions and update the autoload path.
    // Note we don't want to risk removal during iteration; we expect this to be called
    // infrequently.
    auto funcset = function_set.acquire();
    wcstring_list_t autoloadees;
    for (const auto &kv : funcset->funcs) {
        if (kv.second.is_autoload) {
            autoloadees.push_back(kv.first);
        }
    }
    for (const wcstring &name : autoloadees) {
        funcset->remove(name);
    }
    funcset->autoloader.clear();
}