'use strict';

// Per-machine time-parameterised plan. Pure: given a MachineProfile
// snapshot and a target position, computes how long the move will take.
//
// Cases by profile.state:
//   idle / off              startup ladder + ramp from min to target
//   operational             |target − position| / velocity
//   accelerating |
//   decelerating            post-abort residue, same as operational
//   starting                remaining-in-starting + full warmup + ramp from min
//   warmingup               remaining-in-warmingup + ramp from min
//   stopping | coolingdown  non-interruptible deload; cannot contribute flow
//                           in this dispatch — returns null so the scheduler
//                           can exclude the machine from "up" candidates.
//
// Velocity of 0 returns Infinity (misconfigured speed) so the scheduler
// can demote the machine without crashing.

const ACTIVE_OPERATIONAL = new Set(['operational', 'accelerating', 'decelerating']);
const STARTUP_LADDER     = new Set(['starting', 'warmingup']);
const SHUTDOWN_LADDER    = new Set(['stopping', 'coolingdown']);

class MoveTrajectory {
    constructor(profile, { targetPosition } = {}) {
        if (!profile || typeof profile !== 'object') {
            throw new TypeError('MoveTrajectory: profile is required');
        }
        if (!Number.isFinite(targetPosition)) {
            throw new TypeError('MoveTrajectory: targetPosition must be a finite number');
        }
        this.profile = profile;
        this.targetPosition = this._clampToBounds(targetPosition);
    }

    _clampToBounds(p) {
        const { minPosition, maxPosition } = this.profile;
        if (Number.isFinite(minPosition) && p < minPosition) return minPosition;
        if (Number.isFinite(maxPosition) && p > maxPosition) return maxPosition;
        return p;
    }

    // Seconds from "fire" until the machine is delivering flow at
    // targetPosition. Null when the machine is in a non-contributing
    // (shutting-down) state.
    etaToTargetS() {
        const p = this.profile;
        const v = p.velocityPctPerS;
        const target = this.targetPosition;

        if (SHUTDOWN_LADDER.has(p.state)) return null;

        if (!Number.isFinite(v) || v <= 0) return Infinity;

        if (p.state === 'operational' || ACTIVE_OPERATIONAL.has(p.state)) {
            const dist = Math.abs(target - p.position);
            return dist / v;
        }

        if (p.state === 'warmingup') {
            // Remaining warmup, then ramp from minPosition to target.
            // Ramp starts from minPosition because the pump is not moving
            // during warmup — position is held at min.
            const remW = p.remainingTransitionS ?? p.timings.warmingupS;
            const rampDist = Math.max(0, target - p.minPosition);
            return remW + rampDist / v;
        }

        if (p.state === 'starting') {
            // Remaining-in-starting + full warmup duration + ramp from min.
            const remS = p.remainingTransitionS ?? p.timings.startingS;
            const rampDist = Math.max(0, target - p.minPosition);
            return remS + p.timings.warmingupS + rampDist / v;
        }

        // idle / off / emergencystop / maintenance / any non-active state
        // not in the ladders: full startup sequence to operational, then ramp.
        const rampDist = Math.max(0, target - p.minPosition);
        return p.timings.startingS + p.timings.warmingupS + rampDist / v;
    }
}

MoveTrajectory.SHUTDOWN_LADDER = SHUTDOWN_LADDER;
MoveTrajectory.STARTUP_LADDER  = STARTUP_LADDER;

module.exports = MoveTrajectory;