#include "secsgem/config/validate.hpp"

#include <yaml-cpp/yaml.h>

#include <algorithm>
#include <cctype>
#include <cstdint>
#include <set>
#include <string>
#include <string_view>
#include <utility>
#include <vector>

#include "secsgem/gem/control_job_state.hpp"
#include "secsgem/gem/control_state.hpp"
#include "secsgem/gem/process_job_state.hpp"

namespace secsgem::config {

namespace {

namespace gem = secsgem::gem;

// Map yaml-cpp's Mark to a 1-based line number when available.
std::optional<int> line_of(const YAML::Node& n) {
  const auto m = n.Mark();
  if (m.line < 0) return std::nullopt;
  return m.line + 1;  // yaml-cpp marks are 0-based
}

class Sink {
 public:
  Sink(std::vector<ConfigIssue>& out, std::string file)
      : out_(out), file_(std::move(file)) {}

  void error(const std::string& field_path, const std::string& msg,
             const YAML::Node& at = {}) {
    out_.push_back({file_, line_of(at), field_path, msg,
                    ConfigIssue::Severity::Error});
  }

  void warn(const std::string& field_path, const std::string& msg,
            const YAML::Node& at = {}) {
    out_.push_back({file_, line_of(at), field_path, msg,
                    ConfigIssue::Severity::Warning});
  }

 private:
  std::vector<ConfigIssue>& out_;
  std::string file_;
};

bool valid_secs_type(const std::string& t) {
  static const std::set<std::string_view> ok = {
      "ASCII", "BOOLEAN", "BINARY",
      "U1", "U2", "U4", "U8",
      "I1", "I2", "I4", "I8",
      "F4", "F8",
  };
  return ok.count(t) > 0;
}

bool valid_hcack(const std::string& s) {
  static const std::set<std::string_view> ok = {
      "Accept", "InvalidCommand", "CannotDoNow", "ParameterInvalid",
      "AcceptedWillFinishLater", "Rejected", "InvalidObject",
  };
  return ok.count(s) > 0;
}

// Range-checked integer extraction.  Returns nullopt and emits an
// error if the node is missing, non-scalar, or out of range.
template <typename T>
std::optional<T> as_int_in_range(const YAML::Node& n, Sink& sink,
                                  const std::string& path,
                                  int64_t min, int64_t max) {
  if (!n) {
    sink.error(path, "missing required integer");
    return std::nullopt;
  }
  if (!n.IsScalar()) {
    sink.error(path, "expected an integer", n);
    return std::nullopt;
  }
  int64_t v = 0;
  try {
    v = n.as<int64_t>();
  } catch (const YAML::Exception&) {
    sink.error(path, "value `" + n.Scalar() + "` is not a valid integer", n);
    return std::nullopt;
  }
  if (v < min || v > max) {
    sink.error(path, "value " + std::to_string(v) + " out of range [" +
                          std::to_string(min) + ", " + std::to_string(max) +
                          "]",
                n);
    return std::nullopt;
  }
  return static_cast<T>(v);
}

std::optional<std::string> as_nonempty_string(const YAML::Node& n,
                                                Sink& sink,
                                                const std::string& path) {
  if (!n) {
    sink.error(path, "missing required string");
    return std::nullopt;
  }
  if (!n.IsScalar()) {
    sink.error(path, "expected a string", n);
    return std::nullopt;
  }
  auto s = n.as<std::string>();
  if (s.empty()) {
    sink.error(path, "string must not be empty", n);
    return std::nullopt;
  }
  return s;
}

// API-facing names (variables, events, alarms, commands) should be valid
// identifiers: language bindings expose them as kwargs/attributes
// (eq.set(chamber_pressure=...)), where "Chamber Pressure" or "temp-2" can't
// be written. Warning, not error — the wire doesn't care, only bindings do.
void warn_if_not_identifier(const std::optional<std::string>& s, Sink& sink,
                            const std::string& path, const YAML::Node& n) {
  if (!s) return;
  bool ok = !s->empty() &&
            (std::isalpha(static_cast<unsigned char>((*s)[0])) || (*s)[0] == '_');
  for (std::size_t i = 1; ok && i < s->size(); ++i) {
    const auto c = static_cast<unsigned char>((*s)[i]);
    ok = std::isalnum(c) || (*s)[i] == '_';
  }
  if (!ok)
    sink.warn(path, "`" + *s + "` is not identifier-safe " +
                        "([A-Za-z_][A-Za-z0-9_]*); language bindings expose " +
                        "names as kwargs/attributes",
              n);
}

// Validate one entry that has the same (id, name, units, type, value)
// shape as SVID/DVID/ECID.  Returns the parsed id on success so the
// caller can dedupe.
std::optional<uint32_t> validate_typed_entry(
    const YAML::Node& entry, Sink& sink, const std::string& path) {
  auto id = as_int_in_range<uint32_t>(entry["id"], sink, path + ".id",
                                       0, UINT32_MAX);
  warn_if_not_identifier(as_nonempty_string(entry["name"], sink, path + ".name"),
                         sink, path + ".name", entry["name"]);
  if (auto tn = entry["type"]) {
    auto t = tn.as<std::string>();
    if (!valid_secs_type(t)) {
      sink.error(path + ".type",
                 "unknown SECS-II type `" + t +
                     "` (expected one of ASCII/BOOLEAN/BINARY/U1-U8/I1-I8/F4/F8)",
                 tn);
    }
  } else {
    sink.error(path + ".type", "missing required field `type`");
  }
  return id;
}

void validate_equipment_block(YAML::Node& root, Sink& sink) {
  std::set<uint32_t> ceids;
  std::set<uint32_t> alarm_ids;

  if (!root["device"]) {
    sink.error("device", "missing required `device` block");
  } else {
    auto dev = root["device"];
    as_int_in_range<uint16_t>(dev["id"], sink, "device.id", 0, UINT16_MAX);
    as_nonempty_string(dev["model_name"], sink, "device.model_name");
    as_nonempty_string(dev["software_rev"], sink, "device.software_rev");
  }

  if (auto caps = root["capabilities"]; caps && caps.IsSequence()) {
    for (std::size_t i = 0; i < caps.size(); ++i) {
      const auto path = "capabilities[" + std::to_string(i) + "]";
      const auto& c = caps[i];
      as_int_in_range<uint8_t>(c["code"], sink, path + ".code", 0, 255);
      as_nonempty_string(c["name"], sink, path + ".name");
    }
  }

  auto validate_entry_list = [&](const YAML::Node& seq, const char* key,
                                  std::set<uint32_t>* dedupe = nullptr) {
    if (!seq) return;
    if (!seq.IsSequence()) {
      sink.error(key, "expected a sequence", seq);
      return;
    }
    std::set<uint32_t> local;
    for (std::size_t i = 0; i < seq.size(); ++i) {
      const auto path = std::string(key) + "[" + std::to_string(i) + "]";
      auto id = validate_typed_entry(seq[i], sink, path);
      if (id) {
        if (!local.insert(*id).second) {
          sink.error(path + ".id",
                     "duplicate id " + std::to_string(*id) + " in " + key,
                     seq[i]);
        }
        if (dedupe) dedupe->insert(*id);
      }
    }
  };
  validate_entry_list(root["svids"], "svids");
  validate_entry_list(root["dvids"], "dvids");
  validate_entry_list(root["ecids"], "ecids");

  // CEIDs have a simpler shape (id + name).
  if (auto ces = root["ceids"]) {
    if (!ces.IsSequence()) {
      sink.error("ceids", "expected a sequence", ces);
    } else {
      for (std::size_t i = 0; i < ces.size(); ++i) {
        const auto path = "ceids[" + std::to_string(i) + "]";
        auto id = as_int_in_range<uint32_t>(ces[i]["id"], sink, path + ".id",
                                              0, UINT32_MAX);
        warn_if_not_identifier(
            as_nonempty_string(ces[i]["name"], sink, path + ".name"),
            sink, path + ".name", ces[i]["name"]);
        if (id && !ceids.insert(*id).second) {
          sink.error(path + ".id",
                     "duplicate CEID " + std::to_string(*id),
                     ces[i]);
        }
      }
    }
  }

  if (auto als = root["alarms"]) {
    if (!als.IsSequence()) {
      sink.error("alarms", "expected a sequence", als);
    } else {
      for (std::size_t i = 0; i < als.size(); ++i) {
        const auto path = "alarms[" + std::to_string(i) + "]";
        auto id = as_int_in_range<uint32_t>(als[i]["id"], sink, path + ".id",
                                              0, UINT32_MAX);
        as_nonempty_string(als[i]["text"], sink, path + ".text");
        // ALCD lower-7 bits are the category bitmap (E5 §10.3).  Bit 7
        // is the set/clear flag, set at emit time — must not be in YAML.
        as_int_in_range<uint8_t>(als[i]["category"], sink,
                                   path + ".category", 0, 127);
        // Optional local key for name-based APIs (not on the wire). If
        // present it must be non-empty.
        if (als[i]["name"])
          warn_if_not_identifier(
              as_nonempty_string(als[i]["name"], sink, path + ".name"),
              sink, path + ".name", als[i]["name"]);
        if (id && !alarm_ids.insert(*id).second) {
          sink.error(path + ".id",
                     "duplicate ALID " + std::to_string(*id), als[i]);
        }
      }
    }
  }

  if (auto recs = root["recipes"]) {
    if (!recs.IsSequence()) {
      sink.error("recipes", "expected a sequence", recs);
    } else {
      std::set<std::string> seen;
      for (std::size_t i = 0; i < recs.size(); ++i) {
        const auto path = "recipes[" + std::to_string(i) + "]";
        auto id = as_nonempty_string(recs[i]["id"], sink, path + ".id");
        if (!recs[i]["body"]) {
          sink.error(path + ".body", "missing required `body`");
        }
        if (id && !seen.insert(*id).second) {
          sink.error(path + ".id", "duplicate PPID `" + *id + "`", recs[i]);
        }
      }
    }
  }

  if (auto cmds = root["host_commands"]) {
    if (!cmds.IsSequence()) {
      sink.error("host_commands", "expected a sequence", cmds);
    } else {
      std::set<std::string> names;
      for (std::size_t i = 0; i < cmds.size(); ++i) {
        const auto path = "host_commands[" + std::to_string(i) + "]";
        auto name = as_nonempty_string(cmds[i]["name"], sink, path + ".name");
        warn_if_not_identifier(name, sink, path + ".name", cmds[i]["name"]);
        if (auto ack = cmds[i]["ack"]) {
          auto s = ack.as<std::string>();
          if (!valid_hcack(s))
            sink.error(path + ".ack", "unknown HCACK `" + s + "`", ack);
        } else {
          sink.error(path + ".ack", "missing required `ack`");
        }
        if (auto e = cmds[i]["emit_ceid"]) {
          auto v = as_int_in_range<uint32_t>(e, sink, path + ".emit_ceid",
                                               0, UINT32_MAX);
          if (v && !ceids.count(*v)) {
            sink.error(path + ".emit_ceid",
                       "CEID " + std::to_string(*v) +
                           " not declared in `ceids` section",
                       e);
          }
        }
        if (auto a = cmds[i]["set_alarm"]) {
          auto v = as_int_in_range<uint32_t>(a, sink, path + ".set_alarm",
                                               0, UINT32_MAX);
          if (v && !alarm_ids.count(*v)) {
            sink.error(path + ".set_alarm",
                       "ALID " + std::to_string(*v) +
                           " not declared in `alarms` section",
                       a);
          }
        }
        if (auto f = cmds[i]["force_spool"]) {
          if (!f.IsScalar()) sink.error(path + ".force_spool",
                                          "expected a boolean", f);
        }
        if (name && !names.insert(*name).second) {
          sink.error(path + ".name", "duplicate command name `" + *name + "`",
                     cmds[i]);
        }
      }
    }
  }

  if (auto sp = root["spool"]) {
    if (auto s = sp["spoolable_streams"]) {
      if (!s.IsSequence()) {
        sink.error("spool.spoolable_streams", "expected a sequence", s);
      } else {
        for (std::size_t i = 0; i < s.size(); ++i) {
          // SECS-II streams are 1..127 (top bit is the W flag).
          as_int_in_range<uint8_t>(
              s[i], sink,
              "spool.spoolable_streams[" + std::to_string(i) + "]",
              1, 127);
        }
      }
    }
    if (auto m = sp["max_size"]) {
      as_int_in_range<uint32_t>(m, sink, "spool.max_size", 1, INT32_MAX);
    }
  }

  if (auto e = root["emit_on_control_change"]) {
    if (!e.IsNull()) {
      auto v = as_int_in_range<uint32_t>(e, sink, "emit_on_control_change",
                                           0, UINT32_MAX);
      if (v && !ceids.count(*v)) {
        sink.error("emit_on_control_change",
                   "CEID " + std::to_string(*v) +
                       " not declared in `ceids` section",
                   e);
      }
    }
  }
}

YAML::Node try_load(const std::string& path, Sink& sink) {
  try {
    return YAML::LoadFile(path);
  } catch (const YAML::Exception& e) {
    sink.error("", std::string("YAML parse error: ") + e.what());
    return YAML::Node{};
  }
}

}  // namespace

bool ConfigValidator::has_errors() const { return error_count() > 0; }

std::size_t ConfigValidator::error_count() const {
  return static_cast<std::size_t>(std::count_if(
      issues_.begin(), issues_.end(),
      [](const auto& i) { return i.severity == ConfigIssue::Severity::Error; }));
}

std::size_t ConfigValidator::warning_count() const {
  return issues_.size() - error_count();
}

bool ConfigValidator::validate_equipment(const std::string& path) {
  const auto baseline = error_count();
  Sink sink(issues_, path);
  YAML::Node root = try_load(path, sink);
  if (root) validate_equipment_block(root, sink);
  return error_count() == baseline;
}

bool ConfigValidator::validate_control_state(const std::string& path) {
  const auto baseline = error_count();
  Sink sink(issues_, path);
  YAML::Node root = try_load(path, sink);
  if (!root) return false;

  if (auto in = root["initial"]) {
    if (!gem::parse_control_state(in.as<std::string>())) {
      sink.error("initial", "unknown control state `" + in.as<std::string>() + "`",
                 in);
    }
  }

  const auto ts = root["transitions"];
  if (!ts || !ts.IsSequence()) {
    sink.error("transitions", "missing or non-sequence");
    return false;
  }
  for (std::size_t i = 0; i < ts.size(); ++i) {
    const auto path_i = "transitions[" + std::to_string(i) + "]";
    const auto& row = ts[i];
    auto from_n = row["from"];
    auto on_n = row["on"];
    if (!from_n) sink.error(path_i + ".from", "missing required `from`");
    if (!on_n)   sink.error(path_i + ".on",   "missing required `on`");
    if (from_n && !gem::parse_control_state(from_n.as<std::string>())) {
      sink.error(path_i + ".from",
                 "unknown control state `" + from_n.as<std::string>() + "`",
                 from_n);
    }
    if (on_n && !gem::parse_control_event(on_n.as<std::string>())) {
      sink.error(path_i + ".on",
                 "unknown control event `" + on_n.as<std::string>() + "`",
                 on_n);
    }
    if (auto to = row["to"]) {
      if (!gem::parse_control_state(to.as<std::string>())) {
        sink.error(path_i + ".to",
                   "unknown control state `" + to.as<std::string>() + "`",
                   to);
      }
    }
    if (auto th = row["then"]) {
      if (!gem::parse_control_state(th.as<std::string>())) {
        sink.error(path_i + ".then",
                   "unknown control state `" + th.as<std::string>() + "`",
                   th);
      }
    }
  }
  return error_count() == baseline;
}

bool ConfigValidator::validate_process_job_state(const std::string& path) {
  const auto baseline = error_count();
  Sink sink(issues_, path);
  YAML::Node root = try_load(path, sink);
  if (!root) return false;

  if (auto in = root["initial"]) {
    auto parsed = gem::parse_process_job_state(in.as<std::string>());
    if (!parsed) {
      sink.error("initial",
                 "unknown PJ state `" + in.as<std::string>() + "`", in);
    } else if (*parsed == gem::ProcessJobState::NoState) {
      sink.error("initial",
                 "`NoState` is a sentinel and cannot be the initial state",
                 in);
    }
  }

  const auto ts = root["transitions"];
  if (!ts || !ts.IsSequence()) {
    sink.error("transitions", "missing or non-sequence");
    return false;
  }
  for (std::size_t i = 0; i < ts.size(); ++i) {
    const auto path_i = "transitions[" + std::to_string(i) + "]";
    const auto& row = ts[i];
    if (auto from = row["from"]) {
      auto parsed = gem::parse_process_job_state(from.as<std::string>());
      if (!parsed)
        sink.error(path_i + ".from", "unknown PJ state", from);
      else if (*parsed == gem::ProcessJobState::NoState)
        sink.error(path_i + ".from",
                   "`NoState` is a sentinel and cannot appear as `from`", from);
    } else {
      sink.error(path_i + ".from", "missing required `from`");
    }
    if (auto on = row["on"]) {
      if (!gem::parse_process_job_event(on.as<std::string>()))
        sink.error(path_i + ".on", "unknown PJ event", on);
    } else {
      sink.error(path_i + ".on", "missing required `on`");
    }
    if (auto to = row["to"]) {
      auto parsed = gem::parse_process_job_state(to.as<std::string>());
      if (!parsed)
        sink.error(path_i + ".to", "unknown PJ state", to);
      else if (*parsed == gem::ProcessJobState::NoState)
        sink.error(path_i + ".to",
                   "`NoState` is a sentinel and cannot appear as `to`", to);
    }
  }
  return error_count() == baseline;
}

bool ConfigValidator::validate_control_job_state(const std::string& path) {
  const auto baseline = error_count();
  Sink sink(issues_, path);
  YAML::Node root = try_load(path, sink);
  if (!root) return false;

  if (auto in = root["initial"]) {
    if (!gem::parse_control_job_state(in.as<std::string>()))
      sink.error("initial",
                 "unknown CJ state `" + in.as<std::string>() + "`", in);
  }

  const auto ts = root["transitions"];
  if (!ts || !ts.IsSequence()) {
    sink.error("transitions", "missing or non-sequence");
    return false;
  }
  for (std::size_t i = 0; i < ts.size(); ++i) {
    const auto path_i = "transitions[" + std::to_string(i) + "]";
    const auto& row = ts[i];
    if (auto from = row["from"]) {
      if (!gem::parse_control_job_state(from.as<std::string>()))
        sink.error(path_i + ".from", "unknown CJ state", from);
    } else {
      sink.error(path_i + ".from", "missing required `from`");
    }
    if (auto on = row["on"]) {
      if (!gem::parse_control_job_event(on.as<std::string>()))
        sink.error(path_i + ".on", "unknown CJ event", on);
    } else {
      sink.error(path_i + ".on", "missing required `on`");
    }
    if (auto to = row["to"]) {
      if (!gem::parse_control_job_state(to.as<std::string>()))
        sink.error(path_i + ".to", "unknown CJ state", to);
    }
  }
  return error_count() == baseline;
}

void format_issues_to(std::ostream& os,
                       const std::vector<ConfigIssue>& issues) {
  for (const auto& i : issues) {
    os << (i.severity == ConfigIssue::Severity::Error ? "[error] "
                                                       : "[warn]  ")
       << i.file;
    if (i.line) os << ":" << *i.line;
    if (!i.field_path.empty()) os << " " << i.field_path;
    os << " — " << i.message << "\n";
  }
}

}  // namespace secsgem::config