Crate bhtune_core 

bhtune-core — the pure, I/O-free domain crate.

This crate holds (once implemented — see AGENTS.md for phase status):

• The MRFT (Modified Relay Feedback Test) tuning algorithm, as a pure state machine: fn step(&mut self, tick: Tick) -> Vec<Action>. No clock reads, no network calls, no UI access — that constraint is what makes it possible to replay a recorded trace and assert the engine produces bit-identical results across changes.
• The tuning-constant lookup matrices and PID unit conversion math.
• The domain data model: tag maps, loop configuration, DCS/PLC template semantics, and the enums that model PID parameter types and controller direction.

Deliberately has no I/O, no async, and no clock reads (chrono’s clock/now features are disabled workspace-wide, so Utc::now() cannot even compile here — see core-mrft in AGENTS.md). This is a narrower rule than “no dependencies”: toml is a real dependency (template-catalog), justified because parsing an include_str!- embedded &'static str is not I/O; the optional, feature-gated utoipa dependency (openapi-contract) is justified the same way — a compile-time derive macro that describes a type’s shape, with zero runtime behavior of its own. Anything added here must be justified by the pure domain logic itself (or, for utoipa, by describing it accurately to a consumer), not by a consumer’s I/O or presentation needs — those belong in bhtune-driver, bhtune-db, bhtune-cli, or bhtune-server.

Re-exports

pub use constants::ResponseLevel;

pub use constants::TuningConstants;

pub use constants::lookup;

pub use controller_type::ControllerType;

pub use direction::ControllerDirection;

pub use loop_config::LoopConfig;

pub use loop_config::LoopConfigError;

pub use mrft::Action;

pub use mrft::InitialReadings;

pub use mrft::MrftCompat;

pub use mrft::MrftEngine;

pub use mrft::MrftState;

pub use mrft::Tick;

pub use pid_config::DerivativeType;

pub use pid_config::IntegralType;

pub use pid_config::ProportionalType;

pub use pid_config::TimeUnit;

pub use process_type::ProcessType;

pub use range::MvRange;

pub use range::PvRange;

pub use range::RangeError;

pub use tags::LoopTags;

pub use tags::TagOrValue;

pub use tags::TagOverrides;

pub use tags::TagOverridesError;

pub use tags::derive_tag;

pub use template::DcsTemplate;

pub use template::built_in_templates;

pub use tuning_math::CheckedTuningResult;

pub use tuning_math::OpcWriteValues;

pub use tuning_math::Oscillation;

pub use tuning_math::PidParameters;

pub use tuning_math::TuningMathCompat;

pub use tuning_math::TuningResult;

pub use tuning_math::TuningResultInvalidReason;

pub use tuning_math::TuningResultStatus;

pub use tuning_math::calculate_all;

pub use tuning_math::calculate_all_checked;

pub use tuning_math::calculate_pid_parameters;

pub use tuning_math::calculate_tuning_result;

pub use tuning_math::measure_oscillation;

pub use tuning_math::opc_write_values;

Modules

constants

Tuning-constant lookup matrices: per-process-type, per-response-level, per-controller type multipliers used to turn a measured relay-test oscillation into Kp/Ti/Td.

controller_type

The controller structures a tuning run can target: Proportional-only, Proportional + Integral, or full PID.

direction

Controller action direction: whether increasing the manipulated variable increases or decreases the process variable. Determines which way the relay steps during MRFT.

loop_config

Per-run test configuration: process type, controller type, relay amplitude, and MRFT cycle/timing parameters.

mrft

The MRFT (Modified Relay Feedback Test) engine: the pure, I/O-free relay-switching state machine at the heart of bhtune. See AGENTS.md’s “Key architectural decisions” for why this must never read a clock, perform network I/O, or touch a UI.

pid_config

Enums for how a DCS/PLC expresses PID parameters, avoiding the fragile pattern of comparing live values against magic display strings ("Kp - Proportional Gain", etc.).

process_type

The process types the tuning-constant matrices are calibrated for.

range

Validated PV/MV range types – the boundary a live OPC DA read or a CLI flag override must pass through before an untrusted number is treated as a range with a known, trustworthy shape (finite bounds, correctly ordered, non-zero span). See AGENTS.md’s “Live-plant safety hardening” section for the review finding this closes (--cycles-count 0 panicking mid-run was the same finding’s other symptom: no externally supplied number reached the engine validated).

tags

OPC tag-name derivation: expands a single PV tag into the full tag set a loop needs, using the active DCS/PLC template’s suffix conventions.

template

DCS/PLC template semantics: one instance per control-system convention (Yokogawa, Honeywell, etc.), describing how that DCS expresses PID parameters and the OPC item-name suffix convention used to derive a full tag set from a single PV tag (see crate::tags::derive_tag).

tuning_math

Tuning-constant math: turns a completed MRFT run’s peaks/troughs/switch-times into Kp/Ti/Td for all three ResponseLevels, then into the PID parameters in whatever representation/units a DCS/PLC template expects.