from __future__ import annotations

from collections.abc import Iterator, Mapping
from typing import Any

from wf_core.analysis.context_scopes import (
    ContextSchema,
    root_context_schema,
)
from wf_core.analysis.control_regions import ControlRegionAnalysis
from wf_core.context_contracts import RESERVED_CONTEXT_KEYS
from wf_core.models.conditions import (
    BinaryCondition,
    Condition,
    ExistsCondition,
    LiteralOperand,
    NotCondition,
    PathOperand,
    VariadicCondition,
)
from wf_core.models.input_bindings import (
    ArrayExpression,
    InputExpression,
    InputExpressionBinding,
    InputPathBinding,
    LiteralExpression,
    ObjectExpression,
    PathExpression,
)
from wf_core.models.steps import (
    ConditionNode,
    ForeachNode,
    InterruptNode,
    NodeUse,
    SubgraphNode,
)
from wf_core.models.workflow import Workflow
from wf_core.paths import GraphSourcePath
from wf_core.schema_navigation import SchemaNavigator
from wf_core.validation.issues import ValidationIssueCode, ValidationReport


def validate_context_paths(
    workflow: Workflow,
    *,
    context_schemas: Mapping[str, ContextSchema],
    report: ValidationReport,
    control_regions: ControlRegionAnalysis | None = None,
) -> None:
    """Validate every ``context.*`` path against its consuming location schema.

    Ordinary input/state validation stays where it is; this pass owns the
    stronger program-location-aware meaning of ``context.*``. A path is valid
    only if every literal segment is a declared object property in the
    consuming node's generated schema. The whole ``context`` object and the
    ``context.foreach`` map remain readable; unknown dynamic keys do not.
    The shared control-region analysis is threaded through so validation runs
    it once; alias ownership never triggers a second traversal.
    """
    nodes_by_index = list(workflow.nodes)
    node_index_by_id = {node.id: idx for idx, node in enumerate(nodes_by_index)}
    _validate_alias_ownership(
        workflow, node_index_by_id, report, control_regions=control_regions
    )
    for idx, node in enumerate(nodes_by_index):
        schema = context_schemas.get(node.id)
        if isinstance(node, NodeUse):
            _validate_step_input_bindings(
                node.input, f"nodes[{idx}].input", node.id, schema, report
            )
        elif isinstance(node, SubgraphNode):
            _validate_step_input_bindings(
                node.input, f"nodes[{idx}].input", node.id, schema, report
            )
        elif isinstance(node, ConditionNode):
            for location, path in _condition_paths(node.check, f"nodes[{idx}].check"):
                _validate_one_context_path(path, location, node.id, schema, report)
        elif isinstance(node, ForeachNode):
            # Context-rooted `over` paths reach this pass; the old
            # input/state-only check stays permissive for them.
            if node.over.root == "context":
                _validate_context_foreach_source(
                    node.over, f"nodes[{idx}].over", node.id, schema, report
                )
        elif isinstance(node, InterruptNode):
            _validate_step_input_bindings(
                node.request, f"nodes[{idx}].request", node.id, schema, report
            )
    _validate_workflow_output(workflow, report)


def _validate_step_input_bindings(
    bindings: list[Any],
    base: str,
    node_id: str,
    schema: ContextSchema | None,
    report: ValidationReport,
) -> None:
    """Validate context paths in one input/request binding list.

    `base` is the list location such as `nodes[3].input` or
    `nodes[1].request`; each binding contributes `base[i]` and each path
    field contributes a further suffix like `.path` or
    `.expression.items[0].path`.
    """
    for binding_index, binding in enumerate(bindings):
        binding_location = f"{base}[{binding_index}]"
        if isinstance(binding, InputPathBinding):
            if binding.path.root == "context":
                _validate_one_context_path(
                    binding.path, f"{binding_location}.path", node_id, schema, report
                )
        elif isinstance(binding, InputExpressionBinding):
            for location, path in _expression_paths(
                binding.expression, f"{binding_location}.expression"
            ):
                if path.root == "context":
                    _validate_one_context_path(path, location, node_id, schema, report)


def _expression_paths(
    expression: InputExpression,
    location: str,
) -> Iterator[tuple[str, GraphSourcePath]]:
    """Yield ``(model path, graph path)`` for every path leaf in an expression.

    Finite recursion mirrors the input-expression model: paths, arrays, and
    objects. Literals contribute no paths.
    """
    match expression:
        case PathExpression(path=path):
            yield location + ".path", path
        case ArrayExpression(items=items):
            for index, item in enumerate(items):
                yield from _expression_paths(item, f"{location}.items[{index}]")
        case ObjectExpression(fields=fields):
            for name, item in fields.items():
                yield from _expression_paths(item, f"{location}.fields.{name}")
        case LiteralExpression():
            return


def _condition_paths(
    condition: Condition,
    location: str,
) -> Iterator[tuple[str, GraphSourcePath]]:
    """Yield context-candidate paths from a condition tree with model locations."""
    if isinstance(condition, ExistsCondition):
        yield location + ".path", condition.path
        return
    if isinstance(condition, NotCondition):
        yield from _condition_paths(condition.arg, f"{location}.arg")
        return
    if isinstance(condition, VariadicCondition):
        for index, arg in enumerate(condition.args):
            yield from _condition_paths(arg, f"{location}.args[{index}]")
        return
    if isinstance(condition, BinaryCondition):
        yield from _operand_paths(condition.left, f"{location}.left")
        yield from _operand_paths(condition.right, f"{location}.right")
        return


def _operand_paths(
    operand: PathOperand | LiteralOperand, location: str
) -> Iterator[tuple[str, GraphSourcePath]]:
    if isinstance(operand, LiteralOperand):
        return
    yield location + ".path", operand.path


def _validate_one_context_path(
    path: GraphSourcePath,
    location: str,
    node_id: str | None,
    schema: ContextSchema | None,
    report: ValidationReport,
) -> None:
    if path.root != "context":
        return
    if schema is None:
        report.add(
            ValidationIssueCode.INVALID_CONTEXT_PATH,
            location,
            f"invalid context path {str(path)!r} at {node_id or location!r}: "
            "no context schema for this program location",
        )
        return
    failing, available = _failing_segment(schema, path.parts)
    if failing is not None:
        listed = f" (available: {available})" if available else ""
        report.add(
            ValidationIssueCode.INVALID_CONTEXT_PATH,
            location,
            f"invalid context path {str(path)!r} at {node_id or location!r}: "
            f"unknown segment {failing!r}{listed}",
        )


def _validate_context_foreach_source(
    path: GraphSourcePath,
    location: str,
    node_id: str,
    schema: ContextSchema | None,
    report: ValidationReport,
) -> None:
    """Require an existing context path to declare an array source.

    Missing paths keep the more precise ``INVALID_CONTEXT_PATH`` diagnostic;
    this adds the foreach-specific error only after the path resolves.
    """
    _validate_one_context_path(path, location, node_id, schema, report)
    if schema is None:
        return
    source = SchemaNavigator(schema).at_path(path.parts)
    if source is not None and not source.is_array():
        report.add(
            ValidationIssueCode.INVALID_FOREACH_SOURCE,
            location,
            f"foreach source {str(path)!r} must resolve to an array",
        )


def _failing_segment(
    schema: Mapping[str, Any], parts: tuple[str, ...]
) -> tuple[str | None, str]:
    """Return the first unknown segment plus the keys available there.

    Returns ``(None, "")`` when the path walks declared properties (or
    permissive unconstrained schemas). Reference resolution is delegated to
    the shared Draft 2020-12 navigator; unresolvable refs fail closed.
    Composition is a union for path availability: a path is readable when
    some structural branch declares it.
    """
    return SchemaNavigator(schema).first_unknown(parts)


def _validate_workflow_output(workflow: Workflow, report: ValidationReport) -> None:
    schema = root_context_schema()
    for output_index, binding in enumerate(workflow.output):
        if isinstance(binding, InputPathBinding):
            if binding.path.root == "context":
                _validate_one_context_path(
                    binding.path,
                    f"output[{output_index}].path",
                    "workflow_output",
                    schema,
                    report,
                )
        elif isinstance(binding, InputExpressionBinding):
            for location, path in _expression_paths(
                binding.expression, f"output[{output_index}].expression"
            ):
                if path.root == "context":
                    _validate_one_context_path(
                        path, location, "workflow_output", schema, report
                    )


def _validate_alias_ownership(
    workflow: Workflow,
    node_index_by_id: dict[str, int],
    report: ValidationReport,
    *,
    control_regions: ControlRegionAnalysis | None = None,
) -> None:
    """Reject reserved or colliding active foreach aliases.

    Reserved names are every standard context field plus ``foreach``,
    ``loop_item``, and ``loop_index`` (that is, ``RESERVED_CONTEXT_KEYS``).
    Siblings in separate control regions may reuse an alias because they are
    never active together; only aliases active in the same owner stack
    collide. Failures point at the inner foreach's ``as`` field. The shared
    control-region analysis is reused; this helper never traverses alone.
    """
    if control_regions is None:
        from wf_core.analysis.control_regions import analyze_control_regions

        control_regions = analyze_control_regions(workflow)
    analysis = control_regions
    foreach_by_id = {
        node.id: node for node in workflow.nodes if isinstance(node, ForeachNode)
    }
    reported: set[str] = set()
    for stack in analysis.owner_stack_by_node.values():
        seen_aliases: dict[str, str] = {}
        for owner_id in stack:
            foreach = foreach_by_id.get(owner_id)
            if foreach is None:
                continue
            alias = foreach.as_
            idx = node_index_by_id.get(owner_id)
            location = f"nodes[{idx}].as" if idx is not None else f"nodes[{owner_id}]"
            if not alias or alias in RESERVED_CONTEXT_KEYS:
                if owner_id not in reported:
                    reported.add(owner_id)
                    report.add(
                        ValidationIssueCode.FOREACH_CONTEXT_ALIAS_CONFLICT,
                        location,
                        f"foreach alias {alias!r} for node {owner_id!r} "
                        "collides with reserved context keys",
                    )
                continue
            if alias in seen_aliases:
                if owner_id not in reported:
                    reported.add(owner_id)
                    report.add(
                        ValidationIssueCode.FOREACH_CONTEXT_ALIAS_CONFLICT,
                        location,
                        f"foreach alias {alias!r} for node {owner_id!r} "
                        f"collides with active alias from {seen_aliases[alias]!r}",
                    )
                continue
            seen_aliases[alias] = owner_id