import re
from collections.abc import Mapping
from typing import TYPE_CHECKING

import yaml
from pydantic import Field
from pydantic import field_validator
from pydantic import model_validator

from .common import SEMVER_RE
from .common import SKILL_ID_RE
from .common import DocsPath
from .common import StrictFrozenModel
from .common import frozen_mapping

if TYPE_CHECKING:
    from personal_mcp.registry.ingest.prompt import PromptFilesBundle


class PromptArgumentEntry(StrictFrozenModel):
    """Schema for a single prompt argument definition."""

    title: str | None = None
    description: str | None = None
    required: bool = False


class PromptMetadata(StrictFrozenModel):
    """Canonical metadata describing a prompt contract and arguments."""

    id: str
    version: str
    tags: tuple[str, ...] = ()
    capabilities: tuple[str, ...] = Field(min_length=1)
    arguments: Mapping[str, PromptArgumentEntry] = Field(default_factory=frozen_mapping)

    @field_validator("id")
    @classmethod
    def validate_id(cls, value: str) -> str:
        if not SKILL_ID_RE.fullmatch(value):
            raise ValueError("id must be lowercase kebab-case and start with a letter")
        return value

    @field_validator("version")
    @classmethod
    def validate_version(cls, value: str) -> str:
        if not SEMVER_RE.fullmatch(value):
            raise ValueError("version must be semver")
        return value

    @field_validator("tags")
    @classmethod
    def validate_tags(cls, value: tuple[str, ...]) -> tuple[str, ...]:
        for tag in value:
            if not SKILL_ID_RE.fullmatch(tag):
                raise ValueError(f"invalid tag: {tag}")
        return value

    @field_validator("arguments", mode="before")
    @classmethod
    def freeze_arguments(cls, value: Mapping[str, PromptArgumentEntry] | None) -> Mapping[str, PromptArgumentEntry]:
        return frozen_mapping(value)

    @field_validator("arguments")
    @classmethod
    def validate_argument_names(cls, value: Mapping[str, PromptArgumentEntry]) -> Mapping[str, PromptArgumentEntry]:
        for name in value:
            if not re.fullmatch(r"^[A-Za-z_][A-Za-z0-9_]*$", name):
                raise ValueError(f"invalid prompt argument name: {name}")
        return value


class PromptFrontmatter(StrictFrozenModel):
    """Parsed PROMPT frontmatter including personal-mcp metadata."""

    name: str = Field(min_length=1, max_length=64)
    description: str = Field(min_length=1, max_length=1024)
    x_personal_mcp: PromptMetadata = Field(alias="x-personal-mcp")

    @field_validator("name")
    @classmethod
    def validate_name(cls, value: str) -> str:
        if not SKILL_ID_RE.fullmatch(value):
            raise ValueError("name must be lowercase kebab-case and start with a letter")
        if "anthropic" in value or "claude" in value:
            raise ValueError("name must not contain reserved words anthropic or claude")
        return value

    @classmethod
    def from_raw_yaml(cls, raw: str | None) -> "PromptFrontmatter":
        if raw is None:
            raise ValueError("missing YAML frontmatter")
        try:
            data = yaml.safe_load(raw)
        except yaml.YAMLError as e:
            raise ValueError(f"invalid YAML in frontmatter: {e}") from e
        if not isinstance(data, dict):
            raise TypeError("frontmatter must parse to an object")
        return cls.model_validate(data)


class StoredPrompt(StrictFrozenModel):
    """Normalized prompt document content with path and frontmatter for storage in the registry."""

    prompt_id: str
    relpath: DocsPath
    content: str
    frontmatter: PromptFrontmatter

    @field_validator("frontmatter", mode="before")
    @classmethod
    def parse_frontmatter_yaml(cls, value: PromptFrontmatter | str | None) -> PromptFrontmatter:
        if isinstance(value, PromptFrontmatter):
            return value
        return PromptFrontmatter.from_raw_yaml(value)

    @model_validator(mode="after")
    def validate_contract(self) -> "StoredPrompt":
        parts = self.relpath.parts
        if len(parts) < 3 or parts[0] != "prompts":
            raise ValueError("prompt relpath must be under prompts/<slug>/")

        prompt_dir_name = parts[1]
        if self.frontmatter.name != prompt_dir_name:
            raise ValueError("frontmatter name must exactly match prompt directory name")
        if self.frontmatter.x_personal_mcp.id != self.frontmatter.name:
            raise ValueError("x-personal-mcp.id must exactly match name")

        expected_capability = f"resource://prompts/{self.frontmatter.name}/document"
        if expected_capability not in self.frontmatter.x_personal_mcp.capabilities:
            raise ValueError(f"capabilities must include {expected_capability}")

        if self.prompt_id != self.frontmatter.x_personal_mcp.id:
            raise ValueError("prompt_id must exactly match x-personal-mcp.id")
        return self

    @classmethod
    def from_bundle(cls, bundle: "PromptFilesBundle") -> "StoredPrompt":
        frontmatter = PromptFrontmatter.from_raw_yaml(bundle.prompt.frontmatter)
        return cls.model_validate(
            {
                "prompt_id": frontmatter.x_personal_mcp.id,
                "relpath": bundle.prompt.relpath,
                "content": bundle.prompt.content,
                "frontmatter": frontmatter,
            }
        )