"""
Benefit calculation engine.

All benefits convert saved handle-time seconds into dollars via each
site's fully-loaded labour rate per working second. Reduction
percentages come from :data:`tokencalc.scenarios.BENEFIT_PARAMS` —
``realistic`` (pressure-tested) by default; pass ``params="claim"``
to reproduce the Genesys ROI-doc figures for side-by-side comparison.

Every figure scales by the scenario's year realization ramp.
"""

from __future__ import annotations

import pandas as pd

from .inputs import FeatureScope, SiteInput
from .meters import Confidence
from .rollout import NO_ROLLOUT, RolloutPlan
from .scenarios import BENEFIT_PARAMS, Scenario, get_scenario

MONTHS_PER_YEAR = 12


def _param(name: str, params: str) -> float:
    return BENEFIT_PARAMS[name][params]


def _scope_for(feature_scopes: list[FeatureScope] | FeatureScope,
               feature: str) -> FeatureScope | None:
    if isinstance(feature_scopes, FeatureScope):
        return feature_scopes if feature_scopes.feature == feature else None
    return next((s for s in feature_scopes if s.feature == feature), None)


def _df(rows: list[dict]) -> pd.DataFrame:
    return pd.DataFrame(
        rows, columns=["benefit_line", "scope", "annual_value", "confidence"]
    )


def calculate_voice_handle_time_benefit(
    sites: list[SiteInput],
    feature_scope: FeatureScope,
    scenario: str | Scenario,
    year: int,
    params: str = "realistic",
    rollout: RolloutPlan | None = None,
) -> pd.DataFrame:
    """AHT reduction from knowledge surfacing (Agent Copilot).

    Benefit = volume × eligibility × AHT × reduction% × labour rate.
    """
    sc = get_scenario(scenario) if isinstance(scenario, str) else scenario
    ro = rollout or NO_ROLLOUT
    reduction = _param("voice_aht_knowledge_reduction", params)
    realization = sc.realization(year)
    rows = []
    for s in sites:
        if not feature_scope.active(s.site_name, year):
            continue
        eligibility = (
            feature_scope.eligibility_pct
            if feature_scope.eligibility_pct is not None
            else sc.voice_knowledge_eligibility
        )
        seconds_saved = (
            s.voice_volume_monthly * MONTHS_PER_YEAR
            * eligibility * s.voice_aht_seconds * reduction * realization
        )
        rows.append(
            {
                "benefit_line": "Voice AHT (knowledge surfacing)",
                "scope": s.site_name,
                "annual_value": seconds_saved * s.agent_cost_per_second
                * ro.fraction_live(s.site_name, year),
                "confidence": Confidence.ESTIMATED.value,
            }
        )
    return _df(rows)


def calculate_acw_summarization_benefit(
    sites: list[SiteInput],
    feature_scope: FeatureScope,
    scenario: str | Scenario,
    year: int,
    params: str = "realistic",
    rollout: RolloutPlan | None = None,
) -> pd.DataFrame:
    """ACW eliminated by auto-summarization (Copilot / AI Summary)."""
    sc = get_scenario(scenario) if isinstance(scenario, str) else scenario
    ro = rollout or NO_ROLLOUT
    reduction = _param("voice_acw_reduction", params)
    realization = sc.realization(year)
    rows = []
    for s in sites:
        if not feature_scope.active(s.site_name, year):
            continue
        eligibility = (
            feature_scope.eligibility_pct
            if feature_scope.eligibility_pct is not None
            else sc.voice_summarization_eligibility
        )
        seconds_saved = (
            s.voice_volume_monthly * MONTHS_PER_YEAR
            * eligibility * s.voice_acw_seconds * reduction * realization
        )
        rows.append(
            {
                "benefit_line": "Voice ACW (summarization)",
                "scope": s.site_name,
                "annual_value": seconds_saved * s.agent_cost_per_second
                * ro.fraction_live(s.site_name, year),
                "confidence": Confidence.ESTIMATED.value,
            }
        )
    return _df(rows)


def calculate_email_ai_benefit(
    sites: list[SiteInput],
    feature_scope: FeatureScope,
    scenario: str | Scenario,
    year: int,
    params: str = "realistic",
    rollout: RolloutPlan | None = None,
) -> pd.DataFrame:
    """Email Auto-Respond (full displacement at the respond rate) plus
    Auto-Suggest (time saving × acceptance on the remainder)."""
    sc = get_scenario(scenario) if isinstance(scenario, str) else scenario
    ro = rollout or NO_ROLLOUT
    suggest_saving = _param("email_auto_suggest_time_saving", params)
    realization = sc.realization(year)
    rows = []
    for s in sites:
        if not feature_scope.active(s.site_name, year):
            continue
        respond_rate = (
            feature_scope.deflection_target
            if feature_scope.deflection_target is not None
            else sc.email_auto_respond_rate
        )
        annual_emails = s.email_volume_monthly * MONTHS_PER_YEAR
        respond_seconds = (
            annual_emails * respond_rate * s.email_aht_seconds * realization
        )
        suggest_seconds = (
            annual_emails * (1 - respond_rate)
            * sc.email_auto_suggest_acceptance * s.email_aht_seconds
            * suggest_saving * realization
        )
        rate = s.agent_cost_per_second
        rows.append(
            {
                "benefit_line": "Email Auto-Respond (displaced handling)",
                "scope": s.site_name,
                "annual_value": respond_seconds * rate
                * ro.fraction_live(s.site_name, year),
                "confidence": Confidence.UNKNOWN.value,  # meter rate unsourced
            }
        )
        rows.append(
            {
                "benefit_line": "Email Auto-Suggest (drafting time)",
                "scope": s.site_name,
                "annual_value": suggest_seconds * rate
                * ro.fraction_live(s.site_name, year),
                "confidence": Confidence.UNKNOWN.value,
            }
        )
    return _df(rows)


def calculate_sta_benefit(
    sites: list[SiteInput],
    feature_scope: FeatureScope,
    scenario: str | Scenario,
    year: int,
    params: str = "realistic",
    rollout: RolloutPlan | None = None,
) -> pd.DataFrame:
    """STA reduces AHT *indirectly* via coaching — small reduction with
    a realistic ramp (default 1.5% vs the 4% claim)."""
    sc = get_scenario(scenario) if isinstance(scenario, str) else scenario
    ro = rollout or NO_ROLLOUT
    reduction = _param("sta_aht_reduction", params)
    realization = sc.realization(year)
    rows = []
    for s in sites:
        if not feature_scope.active(s.site_name, year):
            continue
        seconds_saved = (
            s.voice_volume_monthly * MONTHS_PER_YEAR
            * s.voice_aht_seconds * reduction * realization
        )
        rows.append(
            {
                "benefit_line": "STA coaching (AHT)",
                "scope": s.site_name,
                "annual_value": seconds_saved * s.agent_cost_per_second
                * ro.fraction_live(s.site_name, year),
                "confidence": Confidence.ESTIMATED.value,
            }
        )
    return _df(rows)


def calculate_bot_deflection_benefit(
    sites: list[SiteInput],
    feature_scope: FeatureScope,
    scenario: str | Scenario,
    year: int,
    params: str = "realistic",
    rollout: RolloutPlan | None = None,
) -> pd.DataFrame:
    """Agent labour avoided on calls deflected to Voice Bot / Agentic VA.

    Not in the original function list but required for a complete net
    case — deflected volume never reaches an agent, so the full AHT is
    avoided.
    """
    sc = get_scenario(scenario) if isinstance(scenario, str) else scenario
    ro = rollout or NO_ROLLOUT
    realization = sc.realization(year)
    rows = []
    for s in sites:
        if not feature_scope.active(s.site_name, year):
            continue
        if feature_scope.feature == "Voice Bot":
            deflection = (
                feature_scope.deflection_target
                if feature_scope.deflection_target is not None
                else sc.voice_bot_deflection
            )
        else:  # Agentic Virtual Agent
            deflection = (
                feature_scope.deflection_target
                if feature_scope.deflection_target is not None
                else sc.agentic_va_deflection
            )
        seconds_saved = (
            s.voice_volume_monthly * MONTHS_PER_YEAR
            * deflection * s.voice_aht_seconds * realization
        )
        rows.append(
            {
                "benefit_line": f"{feature_scope.feature} deflection (labour avoided)",
                "scope": s.site_name,
                "annual_value": seconds_saved * s.agent_cost_per_second
                * ro.fraction_live(s.site_name, year),
                "confidence": Confidence.ESTIMATED.value,
            }
        )
    return _df(rows)


def calculate_supervisor_copilot_benefit(
    sites: list[SiteInput],
    feature_scope: FeatureScope,
    scenario: str | Scenario,
    year: int,
    params: str = "realistic",
    rollout: RolloutPlan | None = None,
) -> pd.DataFrame:
    """Supervisor time reclaimed (summaries, QA triage). ESTIMATED."""
    sc = get_scenario(scenario) if isinstance(scenario, str) else scenario
    ro = rollout or NO_ROLLOUT
    saving = _param("supervisor_copilot_time_saving", params)
    realization = sc.realization(year)
    rows = []
    for s in sites:
        if not feature_scope.active(s.site_name, year):
            continue
        rows.append(
            {
                "benefit_line": "Supervisor time (AI summaries/insights)",
                "scope": s.site_name,
                "annual_value": s.supervisors
                * s.fully_loaded_supervisor_cost_annual
                * saving * realization
                * ro.fraction_live(s.site_name, year),
                "confidence": Confidence.ESTIMATED.value,
            }
        )
    return _df(rows)


def calculate_predictive_routing_benefit(
    sites: list[SiteInput],
    feature_scope: FeatureScope,
    scenario: str | Scenario,
    year: int,
    params: str = "realistic",
    rollout: RolloutPlan | None = None,
) -> pd.DataFrame:
    """Predictive routing AHT effect. ESTIMATED; off unless scoped."""
    sc = get_scenario(scenario) if isinstance(scenario, str) else scenario
    ro = rollout or NO_ROLLOUT
    reduction = _param("predictive_routing_aht_reduction", params)
    realization = sc.realization(year)
    rows = []
    for s in sites:
        if not feature_scope.active(s.site_name, year):
            continue
        seconds_saved = (
            s.voice_volume_monthly * MONTHS_PER_YEAR
            * s.voice_aht_seconds * reduction * realization
        )
        rows.append(
            {
                "benefit_line": "Predictive routing (AHT)",
                "scope": s.site_name,
                "annual_value": seconds_saved * s.agent_cost_per_second
                * ro.fraction_live(s.site_name, year),
                "confidence": Confidence.ESTIMATED.value,
            }
        )
    return _df(rows)


#: Which calculator handles which feature scope.
_BENEFIT_DISPATCH = {
    "Agent Copilot": (
        calculate_voice_handle_time_benefit,
        calculate_acw_summarization_benefit,
    ),
    "AI Summary & Insights": (),  # benefit carried by Copilot where present
    "Speech & Text Analytics": (calculate_sta_benefit,),
    "Voice Bot": (calculate_bot_deflection_benefit,),
    "Agentic Virtual Agent": (calculate_bot_deflection_benefit,),
    "Email AI (Auto-Respond)": (calculate_email_ai_benefit,),
    "Predictive Routing": (calculate_predictive_routing_benefit,),
}


def calculate_total_benefit(
    sites: list[SiteInput],
    feature_scopes: list[FeatureScope],
    scenario: str | Scenario,
    year: int,
    params: str = "realistic",
    include_supervisor_benefit: bool = True,
    rollout: RolloutPlan | None = None,
) -> pd.DataFrame:
    """All benefit lines for one scenario-year, aggregated per line.

    Returns DataFrame: benefit_line, scope, annual_value, confidence.
    """
    sc = get_scenario(scenario) if isinstance(scenario, str) else scenario
    frames: list[pd.DataFrame] = []
    copilot_scope = _scope_for(feature_scopes, "Agent Copilot")

    for scope in feature_scopes:
        for fn in _BENEFIT_DISPATCH.get(scope.feature, ()):  # type: ignore[arg-type]
            frames.append(fn(sites, scope, sc, year, params=params, rollout=rollout))

    if include_supervisor_benefit and copilot_scope is not None:
        frames.append(
            calculate_supervisor_copilot_benefit(
                sites, copilot_scope, sc, year, params=params, rollout=rollout
            )
        )

    frames = [f for f in frames if not f.empty]
    if not frames:
        return _df([])
    detail = pd.concat(frames, ignore_index=True)

    grouped = (
        detail.groupby("benefit_line", sort=False)
        .agg(
            scope=("scope", lambda v: ", ".join(sorted(set(v)))),
            annual_value=("annual_value", "sum"),
            confidence=("confidence", "first"),
        )
        .reset_index()
    )
    return grouped[["benefit_line", "scope", "annual_value", "confidence"]]