// Copyright 2015 Google Inc. All rights reserved
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// +build ignore

#include "dep.h"

#include <algorithm>
#include <iterator>
#include <map>
#include <memory>
#include <unordered_map>
#include <unordered_set>

#include "eval.h"
#include "fileutil.h"
#include "log.h"
#include "rule.h"
#include "stats.h"
#include "strutil.h"
#include "symtab.h"
#include "timeutil.h"
#include "var.h"

namespace {

static vector<DepNode*>* g_dep_node_pool;

static Symbol ReplaceSuffix(Symbol s, Symbol newsuf) {
  string r;
  AppendString(StripExt(s.str()), &r);
  r += '.';
  AppendString(newsuf.str(), &r);
  return Intern(r);
}

void ApplyOutputPattern(const Rule& r,
                        Symbol output,
                        const vector<Symbol>& inputs,
                        vector<Symbol>* out_inputs) {
  if (inputs.empty())
    return;
  if (r.is_suffix_rule) {
    for (Symbol input : inputs) {
      out_inputs->push_back(ReplaceSuffix(output, input));
    }
    return;
  }
  if (r.output_patterns.empty()) {
    copy(inputs.begin(), inputs.end(), back_inserter(*out_inputs));
    return;
  }
  CHECK(r.output_patterns.size() == 1);
  Pattern pat(r.output_patterns[0].str());
  for (Symbol input : inputs) {
    string buf;
    pat.AppendSubst(output.str(), input.str(), &buf);
    out_inputs->push_back(Intern(buf));
  }
}

class RuleTrie {
  struct Entry {
    Entry(const Rule* r, StringPiece s)
        : rule(r), suffix(s) {
    }
    const Rule* rule;
    StringPiece suffix;
  };

 public:
  RuleTrie() {}
  ~RuleTrie() {
    for (auto& p : children_)
      delete p.second;
  }

  void Add(StringPiece name, const Rule* rule) {
    if (name.empty() || name[0] == '%') {
      rules_.push_back(Entry(rule, name));
      return;
    }
    const char c = name[0];
    auto p = children_.emplace(c, nullptr);
    if (p.second) {
      p.first->second = new RuleTrie();
    }
    p.first->second->Add(name.substr(1), rule);
  }

  void Get(StringPiece name, vector<const Rule*>* rules) const {
    for (const Entry& ent : rules_) {
      if ((ent.suffix.empty() && name.empty()) ||
          HasSuffix(name, ent.suffix.substr(1))) {
        rules->push_back(ent.rule);
      }
    }
    if (name.empty())
      return;
    auto found = children_.find(name[0]);
    if (found != children_.end()) {
      found->second->Get(name.substr(1), rules);
    }
  }

  size_t size() const {
    size_t r = rules_.size();
    for (const auto& c : children_)
      r += c.second->size();
    return r;
  }

 private:
  vector<Entry> rules_;
  unordered_map<char, RuleTrie*> children_;
};


bool IsSuffixRule(Symbol output) {
  if (output.empty() || output.str()[0] != '.')
    return false;
  const StringPiece rest = StringPiece(output.str()).substr(1);
  size_t dot_index = rest.find('.');
  // If there is only a single dot or the third dot, this is not a
  // suffix rule.
  if (dot_index == string::npos ||
      rest.substr(dot_index+1).find('.') != string::npos) {
    return false;
  }
  return true;
}

struct RuleMerger {
  vector<const Rule*> rules;
  const Rule* primary_rule;
  bool is_double_colon;

  RuleMerger()
      : primary_rule(nullptr),
        is_double_colon(false) {
  }

  void AddRule(Symbol output, const Rule* r) {
    if (rules.empty()) {
      is_double_colon = r->is_double_colon;
    } else if (is_double_colon != r->is_double_colon) {
      ERROR("%s:%d: *** target file `%s' has both : and :: entries.",
            LOCF(r->loc), output.c_str());
    }

    if (primary_rule && !r->cmds.empty() &&
        !IsSuffixRule(output) && !r->is_double_colon) {
      WARN("%s:%d: warning: overriding commands for target `%s'",
           LOCF(r->cmd_loc()), output.c_str());
      WARN("%s:%d: warning: ignoring old commands for target `%s'",
           LOCF(primary_rule->cmd_loc()), output.c_str());
      primary_rule = r;
    }
    if (!primary_rule && !r->cmds.empty()) {
      primary_rule = r;
    }

    rules.push_back(r);
  }

  void FillDepNodeFromRule(Symbol output,
                           const Rule* r,
                           DepNode* n) const {
    if (is_double_colon)
      copy(r->cmds.begin(), r->cmds.end(), back_inserter(n->cmds));

    ApplyOutputPattern(*r, output, r->inputs, &n->actual_inputs);
    ApplyOutputPattern(*r, output, r->order_only_inputs,
                       &n->actual_order_only_inputs);

    if (r->output_patterns.size() >= 1) {
      CHECK(r->output_patterns.size() == 1);
      n->output_pattern = r->output_patterns[0];
    }
  }

  void FillDepNodeLoc(const Rule* r, DepNode* n) const {
    n->loc = r->loc;
    if (!r->cmds.empty() && r->cmd_lineno)
      n->loc.lineno = r->cmd_lineno;
  }

  void FillDepNode(Symbol output,
                   const Rule* pattern_rule,
                   DepNode* n) const {
    if (primary_rule) {
      CHECK(!pattern_rule);
      FillDepNodeFromRule(output, primary_rule, n);
      FillDepNodeLoc(primary_rule, n);
      n->cmds = primary_rule->cmds;
    } else if (pattern_rule) {
      FillDepNodeFromRule(output, pattern_rule, n);
      FillDepNodeLoc(pattern_rule, n);
      n->cmds = pattern_rule->cmds;
    }

    for (const Rule* r : rules) {
      if (r == primary_rule)
        continue;
      FillDepNodeFromRule(output, r, n);
    }
  }
};

}  // namespace

DepNode::DepNode(Symbol o, bool p, bool r)
    : output(o),
      has_rule(false),
      is_default_target(false),
      is_phony(p),
      is_restat(r),
      rule_vars(NULL),
      depfile_var(NULL),
      output_pattern(Symbol::IsUninitialized()) {
  g_dep_node_pool->push_back(this);
}

class DepBuilder {
 public:
  DepBuilder(Evaluator* ev,
             const vector<const Rule*>& rules,
             const unordered_map<Symbol, Vars*>& rule_vars)
      : ev_(ev),
        rule_vars_(rule_vars),
        implicit_rules_(new RuleTrie()),
        first_rule_(Symbol::IsUninitialized{}),
        depfile_var_name_(Intern(".KATI_DEPFILE")) {
    ScopedTimeReporter tr("make dep (populate)");
    PopulateRules(rules);
    // TODO?
    //LOG_STAT("%zu variables", ev->mutable_vars()->size());
    LOG_STAT("%zu explicit rules", rules_.size());
    LOG_STAT("%zu implicit rules", implicit_rules_->size());
    LOG_STAT("%zu suffix rules", suffix_rules_.size());

    HandleSpecialTargets();
  }

  void HandleSpecialTargets() {
    Loc loc;
    vector<Symbol> targets;

    if (GetRuleInputs(Intern(".PHONY"), &targets, &loc)) {
      for (Symbol t : targets)
        phony_.insert(t);
    }
    if (GetRuleInputs(Intern(".KATI_RESTAT"), &targets, &loc)) {
      for (Symbol t : targets)
        restat_.insert(t);
    }
    if (GetRuleInputs(Intern(".SUFFIXES"), &targets, &loc)) {
      if (targets.empty()) {
        suffix_rules_.clear();
      } else {
        WARN("%s:%d: kati doesn't support .SUFFIXES with prerequisites",
             LOCF(loc));
      }
    }

    // Note we can safely ignore .DELETE_ON_ERROR for --ninja mode.
    static const char* kUnsupportedBuiltinTargets[] = {
      ".DEFAULT",
      ".PRECIOUS",
      ".INTERMEDIATE",
      ".SECONDARY",
      ".SECONDEXPANSION",
      ".IGNORE",
      ".LOW_RESOLUTION_TIME",
      ".SILENT",
      ".EXPORT_ALL_VARIABLES",
      ".NOTPARALLEL",
      ".ONESHELL",
      ".POSIX",
      NULL
    };
    for (const char** p = kUnsupportedBuiltinTargets; *p; p++) {
      if (GetRuleInputs(Intern(*p), &targets, &loc)) {
        WARN("%s:%d: kati doesn't support %s", LOCF(loc), *p);
      }
    }
  }

  ~DepBuilder() {
  }

  void Build(vector<Symbol> targets, vector<DepNode*>* nodes) {
    if (!first_rule_.IsValid()) {
      ERROR("*** No targets.");
    }

    if (!g_flags.gen_all_targets && targets.empty()) {
      targets.push_back(first_rule_);
    }
    if (g_flags.gen_all_targets) {
      unordered_set<Symbol> non_root_targets;
      for (const auto& p : rules_) {
        for (const Rule* r : p.second.rules) {
          for (Symbol t : r->inputs)
            non_root_targets.insert(t);
          for (Symbol t : r->order_only_inputs)
            non_root_targets.insert(t);
        }
      }

      for (const auto& p : rules_) {
        Symbol t = p.first;
        if (!non_root_targets.count(t)) {
          targets.push_back(p.first);
        }
      }
    }

    // TODO: LogStats?

    for (Symbol target : targets) {
      cur_rule_vars_.reset(new Vars);
      ev_->set_current_scope(cur_rule_vars_.get());
      DepNode* n = BuildPlan(target, Intern(""));
      nodes->push_back(n);
      ev_->set_current_scope(NULL);
      cur_rule_vars_.reset(NULL);
    }
  }

 private:
  bool Exists(Symbol target) {
    auto found = rules_.find(target);
    if (found != rules_.end())
      return true;
    if (phony_.count(target))
      return true;
    return ::Exists(target.str());
  }

  bool GetRuleInputs(Symbol s, vector<Symbol>* o, Loc* l) {
    auto found = rules_.find(s);
    if (found == rules_.end())
      return false;

    o->clear();
    CHECK(!found->second.rules.empty());
    *l = found->second.rules.front()->loc;
    for (const Rule* r : found->second.rules) {
      for (Symbol i : r->inputs)
        o->push_back(i);
    }
    return true;
  }

  void PopulateRules(const vector<const Rule*>& rules) {
    for (const Rule* rule : rules) {
      if (rule->outputs.empty()) {
        PopulateImplicitRule(rule);
      } else {
        PopulateExplicitRule(rule);
      }
    }
    for (auto& p : suffix_rules_) {
      reverse(p.second.begin(), p.second.end());
    }
  }

  bool PopulateSuffixRule(const Rule* rule, Symbol output) {
    if (!IsSuffixRule(output))
      return false;

    const StringPiece rest = StringPiece(output.str()).substr(1);
    size_t dot_index = rest.find('.');

    StringPiece input_suffix = rest.substr(0, dot_index);
    StringPiece output_suffix = rest.substr(dot_index+1);
    shared_ptr<Rule> r = make_shared<Rule>(*rule);
    r->inputs.clear();
    r->inputs.push_back(Intern(input_suffix));
    r->is_suffix_rule = true;
    suffix_rules_[output_suffix].push_back(r);
    return true;
  }

  void PopulateExplicitRule(const Rule* rule) {
    for (Symbol output : rule->outputs) {
      if (!first_rule_.IsValid() && output.get(0) != '.') {
        first_rule_ = output;
      }
      rules_[output].AddRule(output, rule);
      PopulateSuffixRule(rule, output);
    }
  }

  static bool IsIgnorableImplicitRule(const Rule* rule) {
    // As kati doesn't have RCS/SCCS related default rules, we can
    // safely ignore suppression for them.
    if (rule->inputs.size() != 1)
      return false;
    if (!rule->order_only_inputs.empty())
      return false;
    if (!rule->cmds.empty())
      return false;
    const string& i = rule->inputs[0].str();
    return (i == "RCS/%,v" || i == "RCS/%" || i == "%,v" ||
            i == "s.%" || i == "SCCS/s.%");
  }

  void PopulateImplicitRule(const Rule* rule) {
    for (Symbol output_pattern : rule->output_patterns) {
      if (output_pattern.str() != "%" || !IsIgnorableImplicitRule(rule))
        implicit_rules_->Add(output_pattern.str(), rule);
    }
  }

  const RuleMerger* LookupRuleMerger(Symbol o) {
    auto found = rules_.find(o);
    if (found != rules_.end()) {
      return &found->second;
    }
    return nullptr;
  }

  Vars* LookupRuleVars(Symbol o) {
    auto found = rule_vars_.find(o);
    if (found != rule_vars_.end())
      return found->second;
    return nullptr;
  }

  bool CanPickImplicitRule(const Rule* rule, Symbol output, DepNode* n,
                           shared_ptr<Rule>* out_rule) {
    Symbol matched(Symbol::IsUninitialized{});
    for (Symbol output_pattern : rule->output_patterns) {
      Pattern pat(output_pattern.str());
      if (pat.Match(output.str())) {
        bool ok = true;
        for (Symbol input : rule->inputs) {
          string buf;
          pat.AppendSubst(output.str(), input.str(), &buf);
          if (!Exists(Intern(buf))) {
            ok = false;
            break;
          }
        }

        if (ok) {
          matched = output_pattern;
          break;
        }
      }
    }
    if (!matched.IsValid())
      return false;

    *out_rule = make_shared<Rule>(*rule);
    if ((*out_rule)->output_patterns.size() > 1) {
      // We should mark all other output patterns as used.
      Pattern pat(matched.str());
      for (Symbol output_pattern : rule->output_patterns) {
        if (output_pattern == matched)
          continue;
        string buf;
        pat.AppendSubst(output.str(), output_pattern.str(), &buf);
        done_[Intern(buf)] = n;
      }
      (*out_rule)->output_patterns.clear();
      (*out_rule)->output_patterns.push_back(matched);
    }

    return true;
  }

  Vars* MergeImplicitRuleVars(Symbol output, Vars* vars) {
    auto found = rule_vars_.find(output);
    if (found == rule_vars_.end())
      return vars;
    if (vars == NULL)
      return found->second;
    // TODO: leak.
    Vars* r = new Vars(*found->second);
    for (auto p : *vars) {
      (*r)[p.first] = p.second;
    }
    return r;
  }

  bool PickRule(Symbol output,
                DepNode* n,
                const RuleMerger** out_rule_merger,
                shared_ptr<Rule>* pattern_rule,
                Vars** out_var) {
    const RuleMerger* rule_merger = LookupRuleMerger(output);
    Vars* vars = LookupRuleVars(output);
    *out_rule_merger = rule_merger;
    *out_var = vars;
    if (rule_merger && rule_merger->primary_rule)
      return true;

    vector<const Rule*> irules;
    implicit_rules_->Get(output.str(), &irules);
    for (auto iter = irules.rbegin(); iter != irules.rend(); ++iter) {
      if (!CanPickImplicitRule(*iter, output, n, pattern_rule))
        continue;
      if (rule_merger) {
        return true;
      }
      CHECK((*pattern_rule)->output_patterns.size() == 1);
      vars = MergeImplicitRuleVars((*pattern_rule)->output_patterns[0], vars);
      *out_var = vars;
      return true;
    }

    StringPiece output_suffix = GetExt(output.str());
    if (output_suffix.get(0) != '.')
      return rule_merger;
    output_suffix = output_suffix.substr(1);

    SuffixRuleMap::const_iterator found = suffix_rules_.find(output_suffix);
    if (found == suffix_rules_.end())
      return rule_merger;

    for (shared_ptr<Rule> irule : found->second) {
      CHECK(irule->inputs.size() == 1);
      Symbol input = ReplaceSuffix(output, irule->inputs[0]);
      if (!Exists(input))
        continue;

      *pattern_rule = irule;
      if (rule_merger)
        return true;
      if (vars) {
        CHECK(irule->outputs.size() == 1);
        vars = MergeImplicitRuleVars(irule->outputs[0], vars);
        *out_var = vars;
      }
      return true;
    }

    return rule_merger;
  }

  DepNode* BuildPlan(Symbol output, Symbol needed_by UNUSED) {
    LOG("BuildPlan: %s for %s",
        output.c_str(),
        needed_by.c_str());

    auto found = done_.find(output);
    if (found != done_.end()) {
      return found->second;
    }

    DepNode* n = new DepNode(output,
                             phony_.count(output),
                             restat_.count(output));
    done_[output] = n;

    const RuleMerger* rule_merger = nullptr;
    shared_ptr<Rule> pattern_rule;
    Vars* vars;
    if (!PickRule(output, n, &rule_merger, &pattern_rule, &vars)) {
      return n;
    }
    if (rule_merger)
      rule_merger->FillDepNode(output, pattern_rule.get(), n);
    else
      RuleMerger().FillDepNode(output, pattern_rule.get(), n);

    vector<unique_ptr<ScopedVar>> sv;
    if (vars) {
      for (const auto& p : *vars) {
        Symbol name = p.first;
        RuleVar* var = reinterpret_cast<RuleVar*>(p.second);
        CHECK(var);
        Var* new_var = var->v();
        if (var->op() == AssignOp::PLUS_EQ) {
          Var* old_var = ev_->LookupVar(name);
          if (old_var->IsDefined()) {
            // TODO: This would be incorrect and has a leak.
            shared_ptr<string> s = make_shared<string>();
            old_var->Eval(ev_, s.get());
            if (!s->empty())
              *s += ' ';
            new_var->Eval(ev_, s.get());
            new_var = new SimpleVar(*s, old_var->Origin());
          }
        } else if (var->op() == AssignOp::QUESTION_EQ) {
          Var* old_var = ev_->LookupVar(name);
          if (old_var->IsDefined()) {
            continue;
          }
        }

        if (name == depfile_var_name_) {
          n->depfile_var = new_var;
        } else {
          sv.emplace_back(new ScopedVar(cur_rule_vars_.get(), name, new_var));
        }
      }
    }

    for (Symbol input : n->actual_inputs) {
      DepNode* c = BuildPlan(input, output);
      n->deps.push_back(c);
    }

    for (Symbol input : n->actual_order_only_inputs) {
      DepNode* c = BuildPlan(input, output);
      n->order_onlys.push_back(c);
    }

    n->has_rule = true;
    n->is_default_target = first_rule_ == output;
    if (cur_rule_vars_->empty()) {
      n->rule_vars = NULL;
    } else {
      n->rule_vars = new Vars;
      for (auto p : *cur_rule_vars_) {
        n->rule_vars->insert(p);
      }
    }

    return n;
  }

  Evaluator* ev_;
  map<Symbol, RuleMerger> rules_;
  const unordered_map<Symbol, Vars*>& rule_vars_;
  unique_ptr<Vars> cur_rule_vars_;

  unique_ptr<RuleTrie> implicit_rules_;
  typedef unordered_map<StringPiece, vector<shared_ptr<Rule>>> SuffixRuleMap;
  SuffixRuleMap suffix_rules_;

  Symbol first_rule_;
  unordered_map<Symbol, DepNode*> done_;
  unordered_set<Symbol> phony_;
  unordered_set<Symbol> restat_;
  Symbol depfile_var_name_;
};

void MakeDep(Evaluator* ev,
             const vector<const Rule*>& rules,
             const unordered_map<Symbol, Vars*>& rule_vars,
             const vector<Symbol>& targets,
             vector<DepNode*>* nodes) {
  DepBuilder db(ev, rules, rule_vars);
  ScopedTimeReporter tr("make dep (build)");
  db.Build(targets, nodes);
}

void InitDepNodePool() {
  g_dep_node_pool = new vector<DepNode*>;
}

void QuitDepNodePool() {
  for (DepNode* n : *g_dep_node_pool)
    delete n;
  delete g_dep_node_pool;
}