"""Application configuration via environment variables / .env file.

All settings are read from the environment (or a .env file in the project
root).  Import :func:`get_settings` wherever you need configuration; the
returned object is cached after the first call.
"""

from __future__ import annotations

from functools import lru_cache

from pydantic import AliasChoices, Field, SecretStr
from pydantic_settings import BaseSettings, SettingsConfigDict


class Settings(BaseSettings):
    """Centralised, env-driven configuration for the codex application."""

    model_config = SettingsConfigDict(
        env_file=".env",
        env_file_encoding="utf-8",
        case_sensitive=False,
        extra="ignore",
    )

    # ------------------------------------------------------------------
    # Database
    # ------------------------------------------------------------------
    database_url: SecretStr = Field(
        default=SecretStr("postgresql://researcher:change_me@localhost:5432/papers"),
        description=(
            "libpq-compatible connection string consumed by psycopg. "
            "Example: postgresql://user:pass@host:5432/dbname"
        ),
    )

    migration_database_url: SecretStr | None = Field(
        default=None,
        description=(
            "Optional privileged connection string used by `codex migrate` to apply "
            "schema DDL. The app's database_url is typically a least-privilege DML "
            "role that cannot CREATE/ALTER owner-held tables (raises "
            "InsufficientPrivilege); point this at an owner/superuser connection. "
            "Falls back to database_url when unset."
        ),
    )

    # ------------------------------------------------------------------
    # External services
    # ------------------------------------------------------------------
    grobid_url: str = Field(
        default="http://localhost:8070",
        description="Base URL of the GROBID HTTP API (containerised).",
    )

    nougat_url: str = Field(
        default="http://localhost:8080",
        validation_alias=AliasChoices("NOUGAT_URL", "nougat_url"),
        description="Base URL of the Nougat OCR HTTP API (containerised).",
    )

    ollama_base_url: str = Field(
        default="http://localhost:11434",
        description="Base URL of the local Ollama endpoint (optional Q&A layer).",
    )

    # ------------------------------------------------------------------
    # Embeddings
    # ------------------------------------------------------------------
    embedding_model: str = Field(
        default="BAAI/bge-m3",
        description=(
            "sentence-transformers model identifier. "
            "Must match EMBEDDING_DIM. Default: BAAI/bge-m3 (1024 dims)."
        ),
    )

    embedding_dim: int = Field(
        default=1024,
        gt=0,
        description=(
            "Dimension of the dense embedding vectors. "
            "Must match the output dimension of EMBEDDING_MODEL."
        ),
    )

    # ------------------------------------------------------------------
    # API etiquette
    # ------------------------------------------------------------------
    openalex_mailto: str = Field(
        default="",
        description=(
            "E-mail address for the OpenAlex Polite Pool (faster rate limits). "
            "Required by OpenAlex ToS for automated access."
        ),
    )

    # ------------------------------------------------------------------
    # F-12 Wiki-Compile
    # ------------------------------------------------------------------
    wiki_dir: str = Field(
        default="wiki/",
        description=(
            "Directory where compiled wiki pages are written. "
            "Relative paths are resolved from the current working directory."
        ),
    )

    wiki_llm_model: str = Field(
        default="qwen2.5:7b",
        description=(
            "Ollama model name used for wiki synthesis. "
            "Must be available at the configured Ollama endpoint (WIKI_LLM_URL or "
            "OLLAMA_BASE_URL). Default: qwen2.5:7b (qwen-light profile on Jetson)."
        ),
    )

    wiki_llm_url: str | None = Field(
        default=None,
        description=(
            "Ollama base URL for wiki synthesis. "
            "When None, falls back to OLLAMA_BASE_URL "
            "(http://192.168.178.103:11434 for the Jetson). "
            "Set WIKI_LLM_URL to override."
        ),
    )

    wiki_top_k: int = Field(
        default=12,
        gt=0,
        description=(
            "Number of top chunks retrieved per concept for wiki synthesis. "
            "Higher values improve recall at the cost of a larger LLM prompt."
        ),
    )

    wiki_min_grounding_rate: float = Field(
        default=0.5,
        ge=0.0,
        le=1.0,
        description=(
            "Minimum fraction of claims that must be grounded for a page to be written "
            "to wiki/<slug>.md. Pages below this threshold are quarantined to "
            "wiki/draft/<slug>.md instead."
        ),
    )

    # ------------------------------------------------------------------
    # F-09 Rich Parsing
    # ------------------------------------------------------------------
    mathpix_app_id: SecretStr | None = Field(
        default=None,
        description=(
            "MathPix App ID for cloud formula extraction. "
            "When None, pix2tex local OCR is used as fallback."
        ),
    )

    mathpix_app_key: SecretStr | None = Field(
        default=None,
        description=(
            "MathPix App Key for cloud formula extraction. "
            "Must be set together with MATHPIX_APP_ID."
        ),
    )

    pix2tex_fallback: bool = Field(
        default=True,
        description=(
            "Enable pix2tex (local LaTeX OCR) as fallback when MathPix credentials "
            "are absent. Set to False to disable formula extraction entirely without creds."
        ),
    )

    figures_dir: str = Field(
        default="figures/",
        description=(
            "Directory where extracted figure images are written. "
            "Relative paths are resolved from the current working directory."
        ),
    )

    # ------------------------------------------------------------------
    # F-13 Synthesis / Lead-Engine
    # ------------------------------------------------------------------
    leads_dir: str = Field(
        default="leads/",
        description=(
            "Directory where synthesis leads are written. "
            "Grounded leads land in <leads_dir>/grounded/, conjectures in "
            "<leads_dir>/conjectures/. INVARIANT: conjectures NEVER touch wiki/."
        ),
    )

    synthesis_llm_model: str = Field(
        default="qwen2.5:7b",
        description=(
            "Ollama model name used for synthesis (connection / gap / improvement / "
            "conjecture). Defaults to the qwen-light profile on the Jetson."
        ),
    )

    synthesis_llm_url: str | None = Field(
        default=None,
        description=("Ollama base URL for synthesis. When None, falls back to OLLAMA_BASE_URL."),
    )

    synthesis_top_k: int = Field(
        default=20,
        gt=0,
        description=(
            "Number of top chunks retrieved per synthesis probe. Higher values "
            "improve recall at the cost of a larger LLM prompt."
        ),
    )

    synthesis_min_grounded_ratio: float = Field(
        default=0.5,
        ge=0.0,
        le=1.0,
        description=(
            "Minimum fraction of claims that must be grounded for a grounded lead "
            "(connection / gap / improvement) to be emitted. Leads below this "
            "threshold are dropped rather than written to leads/grounded/."
        ),
    )

    synthesis_gap_min_coverage: int = Field(
        default=2,
        gt=0,
        description=(
            "A topic is considered a 'gap' candidate when it is covered by fewer "
            "than this many distinct bibkeys in the retrieved top-K."
        ),
    )

    # ------------------------------------------------------------------
    # F-14 MCP Server
    # ------------------------------------------------------------------
    mcp_transport: str = Field(
        default="stdio",
        description=(
            "Transport protocol for the MCP server. "
            "Allowed values: 'stdio' (default) or 'http'. "
            "HTTP transport requires MCP_AUTH_TOKEN to be set."
        ),
    )

    mcp_host: str = Field(
        default="127.0.0.1",
        description="Bind host for HTTP transport (ignored for stdio).",
    )

    mcp_port: int = Field(
        default=8765,
        gt=0,
        description="Bind port for HTTP transport (ignored for stdio).",
    )

    mcp_auth_token: SecretStr | None = Field(
        default=None,
        description=(
            "Bearer token required when mcp_transport='http'. "
            "If HTTP transport is requested but this is None, the server refuses to start."
        ),
    )

    # ------------------------------------------------------------------
    # F-16 Chunk Quality Gate
    # ------------------------------------------------------------------
    chunk_min_chars: int = Field(
        default=60,
        gt=0,
        description=(
            "Minimum character count for a chunk to pass the quality gate. "
            "Chunks shorter than this value are discarded before embedding."
        ),
    )

    chunk_min_alpha_ratio: float = Field(
        default=0.40,
        ge=0.0,
        le=1.0,
        description=(
            "Minimum fraction of alphabetic characters in a chunk. "
            "Chunks with a lower ratio are treated as OCR artefacts and discarded."
        ),
    )

    chunk_max_bib_score: float = Field(
        default=0.70,
        ge=0.0,
        le=1.0,
        description=(
            "Maximum bibliography heuristic score before a chunk is rejected. "
            "Score is based on DOI density, 'et al.' and year-in-brackets patterns."
        ),
    )

    # ------------------------------------------------------------------
    # F-15 Literature Graph
    # ------------------------------------------------------------------
    graph_cite_boost_alpha: float = Field(
        default=0.3,
        ge=0.0,
        le=1.0,
        description=(
            "Weight of the PageRank citation-boost in hybrid search. "
            "boosted_distance = distance / (1 + alpha * pagerank_score) — dividing "
            "lowers the cosine distance of high-PageRank papers (lower = closer). "
            "Set to 0.0 to disable the boost without removing the flag."
        ),
    )

    graph_min_corpus_size: int = Field(
        default=15,
        gt=0,
        description=(
            "Minimum number of ingested papers for citation_pagerank to yield "
            "meaningful rankings. Below this threshold a warning is logged and "
            "uniform scores are returned."
        ),
    )

    graph_min_citing_coverage: float = Field(
        default=0.8,
        ge=0.0,
        le=1.0,
        description=(
            "Minimum share of ingested papers that must have ≥1 out-edge (i.e. "
            "cite something) before `codex graph report` warns. Low citing "
            "coverage starves PageRank/coupling even when the paper count looks "
            "healthy — the share of *citing* papers is what matters (R-D)."
        ),
    )


@lru_cache(maxsize=1)
def get_settings() -> Settings:
    """Return the cached application settings singleton."""
    return Settings()