"""Reporting service layer aggregating deterministic and simulation metrics."""

from __future__ import annotations

from dataclasses import dataclass, field
from datetime import date
import math
from typing import Mapping, Sequence
from urllib.parse import urlencode

from fastapi import Request

from models import FinancialCategory, Project, Scenario
from services.financial import (
    CashFlow,
    ConvergenceError,
    PaybackNotReachedError,
    internal_rate_of_return,
    net_present_value,
    payback_period,
)
from services.simulation import (
    CashFlowSpec,
    SimulationConfig,
    SimulationMetric,
    SimulationResult,
    run_monte_carlo,
)
from services.unit_of_work import UnitOfWork

DEFAULT_DISCOUNT_RATE = 0.1
DEFAULT_ITERATIONS = 500
DEFAULT_PERCENTILES: tuple[float, float, float] = (5.0, 50.0, 95.0)

_COST_CATEGORY_SIGNS: Mapping[FinancialCategory, float] = {
    FinancialCategory.REVENUE: 1.0,
    FinancialCategory.CAPITAL_EXPENDITURE: -1.0,
    FinancialCategory.OPERATING_EXPENDITURE: -1.0,
    FinancialCategory.CONTINGENCY: -1.0,
    FinancialCategory.OTHER: -1.0,
}


@dataclass(frozen=True)
class IncludeOptions:
    """Flags controlling optional sections in report payloads."""

    distribution: bool = False
    samples: bool = False


@dataclass(slots=True)
class ReportFilters:
    """Filter parameters applied when selecting scenarios for a report."""

    scenario_ids: set[int] | None = None
    start_date: date | None = None
    end_date: date | None = None

    def matches(self, scenario: Scenario) -> bool:
        if self.scenario_ids is not None and scenario.id not in self.scenario_ids:
            return False
        if self.start_date and scenario.start_date and scenario.start_date < self.start_date:
            return False
        if self.end_date and scenario.end_date and scenario.end_date > self.end_date:
            return False
        return True

    def to_dict(self) -> dict[str, object]:
        payload: dict[str, object] = {}
        if self.scenario_ids is not None:
            payload["scenario_ids"] = sorted(self.scenario_ids)
        if self.start_date is not None:
            payload["start_date"] = self.start_date
        if self.end_date is not None:
            payload["end_date"] = self.end_date
        return payload


@dataclass(slots=True)
class ScenarioFinancialTotals:
    currency: str | None
    inflows: float
    outflows: float
    net: float
    by_category: dict[str, float]

    def to_dict(self) -> dict[str, object]:
        return {
            "currency": self.currency,
            "inflows": _round_optional(self.inflows),
            "outflows": _round_optional(self.outflows),
            "net": _round_optional(self.net),
            "by_category": {
                key: _round_optional(value) for key, value in sorted(self.by_category.items())
            },
        }


@dataclass(slots=True)
class ScenarioDeterministicMetrics:
    currency: str | None
    discount_rate: float
    compounds_per_year: int
    npv: float | None
    irr: float | None
    payback_period: float | None
    notes: list[str] = field(default_factory=list)

    def to_dict(self) -> dict[str, object]:
        return {
            "currency": self.currency,
            "discount_rate": _round_optional(self.discount_rate, digits=4),
            "compounds_per_year": self.compounds_per_year,
            "npv": _round_optional(self.npv),
            "irr": _round_optional(self.irr, digits=6),
            "payback_period": _round_optional(self.payback_period, digits=4),
            "notes": self.notes,
        }


@dataclass(slots=True)
class ScenarioMonteCarloResult:
    available: bool
    notes: list[str] = field(default_factory=list)
    result: SimulationResult | None = None
    include_samples: bool = False

    def to_dict(self) -> dict[str, object]:
        if not self.available or self.result is None:
            return {
                "available": False,
                "notes": self.notes,
            }

        metrics: dict[str, dict[str, object]] = {}
        for metric, summary in self.result.summaries.items():
            metrics[metric.value] = {
                "mean": _round_optional(summary.mean),
                "std_dev": _round_optional(summary.std_dev),
                "minimum": _round_optional(summary.minimum),
                "maximum": _round_optional(summary.maximum),
                "percentiles": {
                    f"{percentile:g}": _round_optional(value)
                    for percentile, value in sorted(summary.percentiles.items())
                },
                "sample_size": summary.sample_size,
                "failed_runs": summary.failed_runs,
            }

        samples_payload: dict[str, list[float | None]] | None = None
        if self.include_samples and self.result.samples:
            samples_payload = {}
            for metric, samples in self.result.samples.items():
                samples_payload[metric.value] = [
                    _sanitize_float(sample) for sample in samples.tolist()
                ]

        payload: dict[str, object] = {
            "available": True,
            "iterations": self.result.iterations,
            "metrics": metrics,
            "notes": self.notes,
        }
        if samples_payload:
            payload["samples"] = samples_payload
        return payload


@dataclass(slots=True)
class ScenarioReport:
    scenario: Scenario
    totals: ScenarioFinancialTotals
    deterministic: ScenarioDeterministicMetrics
    monte_carlo: ScenarioMonteCarloResult | None

    def to_dict(self) -> dict[str, object]:
        scenario_info = {
            "id": self.scenario.id,
            "project_id": self.scenario.project_id,
            "name": self.scenario.name,
            "description": self.scenario.description,
            "status": self.scenario.status.value if hasattr(self.scenario.status, 'value') else self.scenario.status,
            "start_date": self.scenario.start_date,
            "end_date": self.scenario.end_date,
            "currency": self.scenario.currency,
            "primary_resource": self.scenario.primary_resource.value
            if self.scenario.primary_resource and hasattr(self.scenario.primary_resource, 'value')
            else self.scenario.primary_resource,
            "discount_rate": _round_optional(self.deterministic.discount_rate, digits=4),
            "created_at": self.scenario.created_at,
            "updated_at": self.scenario.updated_at,
            "simulation_parameter_count": len(self.scenario.simulation_parameters or []),
        }
        payload: dict[str, object] = {
            "scenario": scenario_info,
            "financials": self.totals.to_dict(),
            "metrics": self.deterministic.to_dict(),
        }
        if self.monte_carlo is not None:
            payload["monte_carlo"] = self.monte_carlo.to_dict()
        return payload


@dataclass(slots=True)
class AggregatedMetric:
    average: float | None
    minimum: float | None
    maximum: float | None

    def to_dict(self) -> dict[str, object]:
        return {
            "average": _round_optional(self.average),
            "minimum": _round_optional(self.minimum),
            "maximum": _round_optional(self.maximum),
        }


@dataclass(slots=True)
class ProjectAggregates:
    total_inflows: float
    total_outflows: float
    total_net: float
    deterministic_metrics: dict[str, AggregatedMetric]

    def to_dict(self) -> dict[str, object]:
        return {
            "financials": {
                "total_inflows": _round_optional(self.total_inflows),
                "total_outflows": _round_optional(self.total_outflows),
                "total_net": _round_optional(self.total_net),
            },
            "deterministic_metrics": {
                metric: data.to_dict()
                for metric, data in sorted(self.deterministic_metrics.items())
            },
        }


@dataclass(slots=True)
class MetricComparison:
    metric: str
    direction: str
    best: tuple[int, str, float] | None
    worst: tuple[int, str, float] | None
    average: float | None

    def to_dict(self) -> dict[str, object]:
        return {
            "metric": self.metric,
            "direction": self.direction,
            "best": _comparison_entry(self.best),
            "worst": _comparison_entry(self.worst),
            "average": _round_optional(self.average),
        }


def parse_include_tokens(raw: str | None) -> IncludeOptions:
    tokens: set[str] = set()
    if raw:
        for part in raw.split(","):
            token = part.strip().lower()
            if token:
                tokens.add(token)
    if "all" in tokens:
        return IncludeOptions(distribution=True, samples=True)
    return IncludeOptions(
        distribution=bool({"distribution", "monte_carlo", "mc"} & tokens),
        samples="samples" in tokens,
    )


def validate_percentiles(values: Sequence[float] | None) -> tuple[float, ...]:
    if not values:
        return DEFAULT_PERCENTILES
    seen: set[float] = set()
    cleaned: list[float] = []
    for value in values:
        percentile = float(value)
        if percentile < 0.0 or percentile > 100.0:
            raise ValueError("Percentiles must be between 0 and 100.")
        if percentile not in seen:
            seen.add(percentile)
            cleaned.append(percentile)
    if not cleaned:
        return DEFAULT_PERCENTILES
    return tuple(cleaned)


class ReportingService:
    """Coordinates project and scenario reporting aggregation."""

    def __init__(self, uow: UnitOfWork) -> None:
        self._uow = uow

    def project_summary(
        self,
        project: Project,
        *,
        filters: ReportFilters,
        include: IncludeOptions,
        iterations: int,
        percentiles: tuple[float, ...],
    ) -> dict[str, object]:
        scenarios = self._load_scenarios(project.id, filters)
        reports = [
            self._build_scenario_report(
                scenario,
                include_distribution=include.distribution,
                include_samples=include.samples,
                iterations=iterations,
                percentiles=percentiles,
            )
            for scenario in scenarios
        ]
        aggregates = self._aggregate_project(reports)
        return {
            "project": _project_payload(project),
            "scenario_count": len(reports),
            "filters": filters.to_dict(),
            "aggregates": aggregates.to_dict(),
            "scenarios": [report.to_dict() for report in reports],
        }

    def scenario_comparison(
        self,
        project: Project,
        scenarios: Sequence[Scenario],
        *,
        include: IncludeOptions,
        iterations: int,
        percentiles: tuple[float, ...],
    ) -> dict[str, object]:
        reports = [
            self._build_scenario_report(
                self._reload_scenario(scenario.id),
                include_distribution=include.distribution,
                include_samples=include.samples,
                iterations=iterations,
                percentiles=percentiles,
            )
            for scenario in scenarios
        ]
        comparison = {
            metric: data.to_dict()
            for metric, data in self._build_comparisons(reports).items()
        }
        return {
            "project": _project_payload(project),
            "scenarios": [report.to_dict() for report in reports],
            "comparison": comparison,
        }

    def scenario_distribution(
        self,
        scenario: Scenario,
        *,
        include: IncludeOptions,
        iterations: int,
        percentiles: tuple[float, ...],
    ) -> dict[str, object]:
        report = self._build_scenario_report(
            self._reload_scenario(scenario.id),
            include_distribution=True,
            include_samples=include.samples,
            iterations=iterations,
            percentiles=percentiles,
        )
        return {
            "scenario": report.to_dict()["scenario"],
            "summary": report.totals.to_dict(),
            "metrics": report.deterministic.to_dict(),
            "monte_carlo": (
                report.monte_carlo.to_dict() if report.monte_carlo else {
                    "available": False}
            ),
        }

    def _load_scenarios(self, project_id: int, filters: ReportFilters) -> list[Scenario]:
        scenarios = self._uow.scenarios.list_for_project(
            project_id, with_children=True)
        return [scenario for scenario in scenarios if filters.matches(scenario)]

    def _reload_scenario(self, scenario_id: int) -> Scenario:
        return self._uow.scenarios.get(scenario_id, with_children=True)

    def _build_scenario_report(
        self,
        scenario: Scenario,
        *,
        include_distribution: bool,
        include_samples: bool,
        iterations: int,
        percentiles: tuple[float, ...],
    ) -> ScenarioReport:
        cash_flows, totals = _build_cash_flows(scenario)
        deterministic = _calculate_deterministic_metrics(
            scenario, cash_flows, totals)
        monte_carlo: ScenarioMonteCarloResult | None = None
        if include_distribution:
            monte_carlo = _run_monte_carlo(
                scenario,
                cash_flows,
                include_samples=include_samples,
                iterations=iterations,
                percentiles=percentiles,
            )
        return ScenarioReport(
            scenario=scenario,
            totals=totals,
            deterministic=deterministic,
            monte_carlo=monte_carlo,
        )

    def _aggregate_project(self, reports: Sequence[ScenarioReport]) -> ProjectAggregates:
        total_inflows = sum(report.totals.inflows for report in reports)
        total_outflows = sum(report.totals.outflows for report in reports)
        total_net = sum(report.totals.net for report in reports)

        metrics: dict[str, AggregatedMetric] = {}
        for metric_name in ("npv", "irr", "payback_period"):
            values = [
                getattr(report.deterministic, metric_name)
                for report in reports
                if getattr(report.deterministic, metric_name) is not None
            ]
            if values:
                metrics[metric_name] = AggregatedMetric(
                    average=sum(values) / len(values),
                    minimum=min(values),
                    maximum=max(values),
                )
        return ProjectAggregates(
            total_inflows=total_inflows,
            total_outflows=total_outflows,
            total_net=total_net,
            deterministic_metrics=metrics,
        )

    def _build_comparisons(
        self, reports: Sequence[ScenarioReport]
    ) -> Mapping[str, MetricComparison]:
        comparisons: dict[str, MetricComparison] = {}
        for metric_name, direction in (
            ("npv", "higher_is_better"),
            ("irr", "higher_is_better"),
            ("payback_period", "lower_is_better"),
        ):
            entries: list[tuple[int, str, float]] = []
            for report in reports:
                value = getattr(report.deterministic, metric_name)
                if value is None:
                    continue
                entries.append(
                    (report.scenario.id, report.scenario.name, value))
            if not entries:
                continue
            if direction == "higher_is_better":
                best = max(entries, key=lambda item: item[2])
                worst = min(entries, key=lambda item: item[2])
            else:
                best = min(entries, key=lambda item: item[2])
                worst = max(entries, key=lambda item: item[2])
            average = sum(item[2] for item in entries) / len(entries)
            comparisons[metric_name] = MetricComparison(
                metric=metric_name,
                direction=direction,
                best=best,
                worst=worst,
                average=average,
            )
        return comparisons

    def build_project_summary_context(
        self,
        project: Project,
        filters: ReportFilters,
        include: IncludeOptions,
        iterations: int,
        percentiles: tuple[float, ...],
        request: Request,
    ) -> dict[str, object]:
        """Build template context for project summary page."""
        scenarios = self._load_scenarios(project.id, filters)
        reports = [
            self._build_scenario_report(
                scenario,
                include_distribution=include.distribution,
                include_samples=include.samples,
                iterations=iterations,
                percentiles=percentiles,
            )
            for scenario in scenarios
        ]
        aggregates = self._aggregate_project(reports)

        return {
            "request": request,
            "project": _project_payload(project),
            "scenario_count": len(reports),
            "aggregates": aggregates.to_dict(),
            "scenarios": [report.to_dict() for report in reports],
            "filters": filters.to_dict(),
            "include_options": include,
            "iterations": iterations,
            "percentiles": percentiles,
            "title": f"Project Summary · {project.name}",
            "subtitle": "Aggregated financial and simulation insights across scenarios.",
            "actions": [
                {
                    "href": request.url_for(
                        "reports.project_summary",
                        project_id=project.id,
                    ),
                    "label": "Download JSON",
                }
            ],
        }

    def build_scenario_comparison_context(
        self,
        project: Project,
        scenarios: Sequence[Scenario],
        include: IncludeOptions,
        iterations: int,
        percentiles: tuple[float, ...],
        request: Request,
    ) -> dict[str, object]:
        """Build template context for scenario comparison page."""
        reports = [
            self._build_scenario_report(
                self._reload_scenario(scenario.id),
                include_distribution=include.distribution,
                include_samples=include.samples,
                iterations=iterations,
                percentiles=percentiles,
            )
            for scenario in scenarios
        ]
        comparison = {
            metric: data.to_dict()
            for metric, data in self._build_comparisons(reports).items()
        }

        comparison_json_url = request.url_for(
            "reports.project_scenario_comparison",
            project_id=project.id,
        )
        scenario_ids = [str(s.id) for s in scenarios]
        comparison_query = urlencode(
            [("scenario_ids", str(identifier)) for identifier in scenario_ids]
        )
        if comparison_query:
            comparison_json_url = f"{comparison_json_url}?{comparison_query}"

        return {
            "request": request,
            "project": _project_payload(project),
            "scenarios": [report.to_dict() for report in reports],
            "comparison": comparison,
            "include_options": include,
            "iterations": iterations,
            "percentiles": percentiles,
            "title": f"Scenario Comparison · {project.name}",
            "subtitle": "Evaluate deterministic metrics and Monte Carlo trends side by side.",
            "actions": [
                {
                    "href": comparison_json_url,
                    "label": "Download JSON",
                }
            ],
        }

    def build_scenario_distribution_context(
        self,
        scenario: Scenario,
        include: IncludeOptions,
        iterations: int,
        percentiles: tuple[float, ...],
        request: Request,
    ) -> dict[str, object]:
        """Build template context for scenario distribution page."""
        report = self._build_scenario_report(
            self._reload_scenario(scenario.id),
            include_distribution=True,
            include_samples=include.samples,
            iterations=iterations,
            percentiles=percentiles,
        )

        return {
            "request": request,
            "scenario": report.to_dict()["scenario"],
            "summary": report.totals.to_dict(),
            "metrics": report.deterministic.to_dict(),
            "monte_carlo": (
                report.monte_carlo.to_dict() if report.monte_carlo else {
                    "available": False}
            ),
            "include_options": include,
            "iterations": iterations,
            "percentiles": percentiles,
            "title": f"Scenario Distribution · {scenario.name}",
            "subtitle": "Deterministic and simulated distributions for a single scenario.",
            "actions": [
                {
                    "href": request.url_for(
                        "reports.scenario_distribution",
                        scenario_id=scenario.id,
                    ),
                    "label": "Download JSON",
                }
            ],
        }


def _build_cash_flows(scenario: Scenario) -> tuple[list[CashFlow], ScenarioFinancialTotals]:
    cash_flows: list[CashFlow] = []
    by_category: dict[str, float] = {}
    inflows = 0.0
    outflows = 0.0
    net = 0.0
    period_index = 0

    for financial_input in scenario.financial_inputs or []:
        sign = _COST_CATEGORY_SIGNS.get(financial_input.category, -1.0)
        amount = float(financial_input.amount) * sign
        net += amount
        if amount >= 0:
            inflows += amount
        else:
            outflows += -amount
        by_category.setdefault(financial_input.category.value, 0.0)
        by_category[financial_input.category.value] += amount

        if financial_input.effective_date is not None:
            cash_flows.append(
                CashFlow(amount=amount, date=financial_input.effective_date)
            )
        else:
            cash_flows.append(
                CashFlow(amount=amount, period_index=period_index))
            period_index += 1

    currency = scenario.currency
    if currency is None and scenario.financial_inputs:
        currency = scenario.financial_inputs[0].currency

    totals = ScenarioFinancialTotals(
        currency=currency,
        inflows=inflows,
        outflows=outflows,
        net=net,
        by_category=by_category,
    )
    return cash_flows, totals


def _calculate_deterministic_metrics(
    scenario: Scenario,
    cash_flows: Sequence[CashFlow],
    totals: ScenarioFinancialTotals,
) -> ScenarioDeterministicMetrics:
    notes: list[str] = []
    discount_rate = _normalise_discount_rate(scenario.discount_rate)
    if scenario.discount_rate is None:
        notes.append(
            f"Discount rate not set; defaulted to {discount_rate:.2%}."
        )

    if not cash_flows:
        notes.append(
            "No financial inputs available for deterministic metrics.")
        return ScenarioDeterministicMetrics(
            currency=totals.currency,
            discount_rate=discount_rate,
            compounds_per_year=1,
            npv=None,
            irr=None,
            payback_period=None,
            notes=notes,
        )

    npv_value: float | None
    try:
        npv_value = net_present_value(
            discount_rate,
            cash_flows,
            compounds_per_year=1,
        )
    except ValueError as exc:
        npv_value = None
        notes.append(f"NPV unavailable: {exc}.")

    irr_value: float | None
    try:
        irr_value = internal_rate_of_return(
            cash_flows,
            compounds_per_year=1,
        )
    except (ValueError, ConvergenceError) as exc:
        irr_value = None
        notes.append(f"IRR unavailable: {exc}.")

    payback_value: float | None
    try:
        payback_value = payback_period(
            cash_flows,
            compounds_per_year=1,
        )
    except (ValueError, PaybackNotReachedError) as exc:
        payback_value = None
        notes.append(f"Payback period unavailable: {exc}.")

    return ScenarioDeterministicMetrics(
        currency=totals.currency,
        discount_rate=discount_rate,
        compounds_per_year=1,
        npv=npv_value,
        irr=irr_value,
        payback_period=payback_value,
        notes=notes,
    )


def _run_monte_carlo(
    scenario: Scenario,
    cash_flows: Sequence[CashFlow],
    *,
    include_samples: bool,
    iterations: int,
    percentiles: tuple[float, ...],
) -> ScenarioMonteCarloResult:
    if not cash_flows:
        return ScenarioMonteCarloResult(
            available=False,
            notes=["No financial inputs available for Monte Carlo simulation."],
        )

    discount_rate = _normalise_discount_rate(scenario.discount_rate)
    specs = [CashFlowSpec(cash_flow=flow) for flow in cash_flows]
    notes: list[str] = []
    if not scenario.simulation_parameters:
        notes.append(
            "Scenario has no stochastic parameters; simulation mirrors deterministic cash flows."
        )
    config = SimulationConfig(
        iterations=iterations,
        discount_rate=discount_rate,
        metrics=(
            SimulationMetric.NPV,
            SimulationMetric.IRR,
            SimulationMetric.PAYBACK,
        ),
        percentiles=percentiles,
        return_samples=include_samples,
    )
    try:
        result = run_monte_carlo(specs, config)
    except Exception as exc:  # pragma: no cover - safeguard for unexpected failures
        notes.append(f"Simulation failed: {exc}.")
        return ScenarioMonteCarloResult(available=False, notes=notes)
    return ScenarioMonteCarloResult(
        available=True,
        notes=notes,
        result=result,
        include_samples=include_samples,
    )


def _normalise_discount_rate(value: float | None) -> float:
    if value is None:
        return DEFAULT_DISCOUNT_RATE
    rate = float(value)
    if rate > 1.0:
        return rate / 100.0
    return rate


def _sanitize_float(value: float | None) -> float | None:
    if value is None:
        return None
    if math.isnan(value) or math.isinf(value):
        return None
    return float(value)


def _round_optional(value: float | None, *, digits: int = 2) -> float | None:
    clean = _sanitize_float(value)
    if clean is None:
        return None
    return round(clean, digits)


def _comparison_entry(entry: tuple[int, str, float] | None) -> dict[str, object] | None:
    if entry is None:
        return None
    scenario_id, name, value = entry
    return {
        "scenario_id": scenario_id,
        "name": name,
        "value": _round_optional(value),
    }


def _project_payload(project: Project) -> dict[str, object]:
    return {
        "id": project.id,
        "name": project.name,
        "location": project.location,
        "operation_type": project.operation_type.value,
        "description": project.description,
        "created_at": project.created_at,
        "updated_at": project.updated_at,
    }