"""Scaffold new wiki pages from type-spec templates.

These commands produce structurally-correct frontmatter and a body
skeleton with TODO placeholders by loading templates from type-spec files.
The prose (Description, Summary, Key Takeaways, ...) is still written by the
LLM afterwards with its normal edit tool.

The split between type-spec templates and LLM-provided prose is intentional:
type definitions (naming, frontmatter shape, directory placement, templates) are
deterministic and stored in /types/; the content is judgment and provided by the LLM.

Frontmatter defaults, enum validity, and required-ness all come from the
type's `.schema.yaml` (via `TypeResolver`) - nothing here re-declares them.
Directory placement for subtype-driven types (currently just entities) also
comes from the type-spec, via its `layout:` frontmatter (see
`TypeResolver.get_layout`) - not a hand-maintained Python dict.
"""
from __future__ import annotations

from pathlib import Path
import datetime
from typing import Any, Dict, Optional
import re

import typer

from chemenu import config
from chemenu.commands._util import (
    check_collision,
    check_raw_files_exist,
    fail,
    parse_set_fields,
    rel_path,
    success,
)
from chemenu.frontmatter_io import write_page
from chemenu.type_resolver import resolver


def _default_summary(summary: str) -> str:
    """Scaffold-time placeholder for an unfilled --summary, so schema
    validation's `summary` minLength requirement doesn't block page creation.
    Matches the same "TODO: add summary" text index_build.py already falls
    back to when a page has no frontmatter summary."""
    return summary.strip() or "TODO: add summary"


def _resolve_type_and_get_template(type_path: str, source_dir: Path = None):
    """Resolve a type path, load the type-spec, and extract its template."""
    type_spec = resolver.load_type_spec(type_path, source_dir)
    template = resolver.extract_template(type_spec)
    return type_spec, template


def _enum_help(type_path: str, field_name: str) -> str:
    """Build a help string from the schema's own enum, so any text listing a
    field's valid values can never drift from what the schema accepts."""
    return f"One of: {'|'.join(resolver.get_enum(type_path, field_name))}"


def _parse_date(field_name: str, text: str) -> datetime.date:
    """A `--set <date field>=<value>` as a real date, or a refusal naming it."""
    try:
        return datetime.date.fromisoformat(text)
    except ValueError:
        fail(f"--set {field_name}={text!r} must be YYYY-MM-DD.")


def _build_frontmatter(
    type_path: str, schema: Optional[Dict[str, Any]], today: datetime.date, explicit: Dict[str, Any]
) -> Dict[str, Any]:
    """Build a page's frontmatter dict in schema-declaration order.

    `explicit` supplies every CLI-derived value the caller already has;
    fields not in `explicit` get a type-appropriate default (today's date for
    date-formatted fields, the scaffold placeholder for `summary`, the
    schema's own `default:` where declared, an empty list for arrays), or are
    omitted entirely if optional with no sensible default (e.g.
    `source_url`). This is what lets frontmatter shape - and scaffold-time
    defaults like `provenance: general` - follow the schema instead of being
    hand-declared per CLI command.
    """
    frontmatter: Dict[str, Any] = {"type": type_path}
    for field_name, field_schema in (schema or {}).get("properties", {}).items():
        if field_name == "type":
            continue
        if field_name in explicit:
            value = explicit[field_name]
            # A `--set date=2026-08-23` arrives as a string; the corpus stores
            # dates as `datetime.date`, and the schema already says which fields
            # those are. Converting here keeps one representation on disk instead
            # of leaving it to whoever wrote the CLI call.
            if field_schema.get("format") == "date" and isinstance(value, str):
                value = _parse_date(field_name, value)
            frontmatter[field_name] = value
        elif field_name == "summary":
            frontmatter[field_name] = _default_summary("")
        elif field_name == "author":
            resolved_author = config.default_author()
            if resolved_author is None:
                fail(
                    "No author configured for this instance. Set `git config user.name`, "
                    "or export WIKI_AUTHOR to override it, then retry."
                )
            frontmatter[field_name] = resolved_author
        elif field_schema.get("format") == "date":
            frontmatter[field_name] = today
        elif "default" in field_schema:
            frontmatter[field_name] = field_schema["default"]
        elif field_schema.get("type") == "array":
            frontmatter[field_name] = []

    # Carry through any caller-supplied field the schema doesn't declare,
    # rather than silently dropping it: a typo'd `--set` must surface as a
    # validation error (via `additionalProperties: false`) instead of being
    # quietly ignored, and a schema that does allow extra properties should
    # keep them.
    for field_name, value in explicit.items():
        if field_name not in frontmatter:
            frontmatter[field_name] = value
    return frontmatter


def _filter_bullets(value: Any) -> str:
    """Render a list frontmatter field as `- [[item]]` bullet lines."""
    items = value or []
    return "\n".join(f"- [[{item}]]" for item in items) if items else "- None identified"


def _filter_join(value: Any) -> str:
    """Comma-join a list frontmatter field."""
    return ", ".join(value or [])


def _filter_capitalize(value: Any) -> str:
    return str(value).capitalize()


def _filter_table_header(value: Any) -> str:
    """Render an array field as wikilinked markdown table column headers."""
    return " | ".join(f"[[{item}]]" for item in (value or []))


def _filter_table_sep(value: Any) -> str:
    """Render the markdown table separator row for an array field, one
    column per item."""
    return "|".join("--------" for _ in (value or [])) or "--------"


def _filter_table_cells(value: Any) -> str:
    """Render a placeholder table body row, one cell per array item."""
    return " | ".join("..." for _ in (value or []))


_TEMPLATE_FILTERS = {
    "bullets": _filter_bullets,
    "join": _filter_join,
    "capitalize": _filter_capitalize,
    "table_header": _filter_table_header,
    "table_sep": _filter_table_sep,
    "table_cells": _filter_table_cells,
}


def _apply_template_variables(template: str, variables: Dict[str, Any]) -> str:
    """Apply variable substitutions to a template string.

    Supports:
      - `{field}` - plain substitution from `variables[field]`
      - `{field|filter}` - apply a named filter (bullets, join, capitalize)
        to `variables[field]`'s value, so templates can render list/enum
        frontmatter fields directly instead of the caller precomputing a
        separate display-only variable for each one
      - `{field|literal text}` - literal fallback if `field` isn't in
        `variables` at all and the suffix isn't a recognized filter name
    """
    def replace_match(match: re.Match) -> str:
        full_match = match.group(0)
        var_name = match.group(1)
        if '|' in var_name:
            var_name, suffix = var_name.split('|', 1)
            var_name = var_name.strip()
            suffix = suffix.strip()
            if var_name not in variables:
                return suffix
            value = variables[var_name]
            filter_fn = _TEMPLATE_FILTERS.get(suffix)
            return filter_fn(value) if filter_fn else str(value)
        return str(variables.get(var_name, full_match))

    pattern = r'\{([^}]+)\}'
    return re.sub(pattern, replace_match, template)


def _page_subdir(subtype: Optional[str], type_path: str) -> Optional[str]:
    """Return the subtype-driven subdirectory under a type's `base_dir`, from
    the type-spec's own `layout:` frontmatter. Thin wrapper over
    `TypeResolver.subtype_dir` - the one place this computation lives, shared
    with `move` and `lint`'s misplaced-page finding."""
    return resolver.subtype_dir(type_path, subtype)


def _target_dir(type_path: str, frontmatter: Dict[str, Any]) -> Path:
    """Resolve where an instance of this type is written: `<root>/<base_dir>`,
    plus a subtype subdirectory when the type declares a `layout:`.

    Thin wrapper over `TypeResolver.compute_target_dir` - the one placement
    rule, also used by `move` and `lint`'s misplaced-page finding -
    converting its `ValueError` into the CLI's normal friendly-failure path.

    `base_dir` is resolved against `config.KB_DIR` by default, so tests that
    point KB_DIR at a temporary fixture wiki can never write into the real
    `kb/`. A type-spec declaring `root: repo` resolves against `config.ROOT`
    instead - for artifacts that are agent-directed material rather than
    knowledge, and so live outside the knowledge layer."""
    try:
        return resolver.compute_target_dir(type_path, frontmatter)
    except ValueError as exc:
        fail(str(exc))


def _validate_or_fail(frontmatter: Dict[str, Any], type_path: str, source_dir: Path) -> None:
    """Validate frontmatter against its type-spec schema, converting a
    ValueError into the CLI's normal friendly-failure path instead of an
    uncaught traceback. The schema's own error message (which already names
    the offending field and, for enums, lists the valid values) is shown
    as-is - there is no separate hand-maintained validity check to keep in
    sync with it."""
    try:
        resolver.validate_frontmatter(frontmatter, type_path, source_dir)
    except ValueError as exc:
        fail(str(exc))


def _load_type_or_fail(type_path: str, source_dir: Path):
    """Resolve a type path and load its type-spec + template, converting an
    unresolvable/invalid `--type` into the CLI's normal friendly-failure path."""
    try:
        return _resolve_type_and_get_template(type_path, source_dir)
    except ValueError as exc:
        fail(str(exc))


def new_page_command(
    type_name: str = typer.Argument(
        ...,
        help="Type name, e.g. entity|concept|source|comparison (see `wikitool types list`)",
    ),
    name: str = typer.Option(..., "--name", help="Page title (a type's title_prefix is added automatically)"),
    type_path_override: str = typer.Option(
        "", "--type", help="Override the type-spec path (defaults to the one named by TYPE_NAME)"
    ),
    set_fields: Optional[list[str]] = typer.Option(
        None,
        "--set",
        help="Frontmatter field, repeatable: --set entity_type=tool --set tags=a,b. Array values split on commas (escape a literal one as \\,); repeating --set for an array field appends instead of replacing",
    ),
):
    """Scaffold a new wiki page of any type.

    The type's own type-spec drives everything: which frontmatter fields
    exist and are required (its `.schema.yaml`), their scaffold defaults
    (schema `default:`), where the page is written (`base_dir` + `layout`),
    what prefixes its title (`title_prefix`), and its body skeleton (the
    type-spec's template). Adding a new type therefore needs no change here.
    """
    type_path = type_path_override or resolver.find_type_by_name(type_name)
    if not type_path:
        available = sorted(fm.get("name") for _, fm in resolver.list_type_specs())
        fail(f"No type-spec named '{type_name}'. Available: {', '.join(available)}")

    today = datetime.date.today()

    try:
        title_prefix = resolver.get_title_prefix(type_path)
        root = resolver.get_root(type_path)
    except ValueError as exc:
        fail(str(exc))
    page_title = f"{title_prefix}{name}"
    if root == "kb":
        # Title collisions matter because wikilinks resolve by title alone, so
        # two pages sharing a stem are indistinguishable to every link in the
        # wiki. Artifacts outside kb/ are not addressed by title and are not
        # part of that namespace, so the check does not apply to them.
        check_collision(page_title)

    schema = resolver.get_schema(type_path)
    explicit = parse_set_fields(set_fields, schema)
    declared = (schema or {}).get("properties", {})
    if "summary" in declared:
        explicit.setdefault("summary", _default_summary(""))
    if "name" in declared:
        # The CLI already has this value; a type that stores its own name in
        # frontmatter should not have to be told it twice.
        explicit.setdefault("name", name)
    if "description" in declared:
        explicit.setdefault("description", "TODO: add description")

    frontmatter = _build_frontmatter(type_path, schema, today, explicit)

    # Capture fields (Gitea #67, e.g. `fidelity`/`authority` on a source page)
    # are deliberately absent from `required:` - putting them there would make
    # every existing instance's source pages stop validating, a
    # boundary-crossing change (version-parts.md). The requirement is instead
    # enforced here, in the tool, exactly like `source_type`'s no-default
    # refusal (#66) reads from the schema alone: without a `default:` and
    # omitted from `explicit`, a capture field simply never lands in
    # `frontmatter`, so its absence has to be caught before it is silently
    # written as a page with no capture record at all.
    try:
        capture_fields = resolver.get_capture_fields(type_path)
    except ValueError as exc:
        fail(str(exc))
    missing_capture = [f for f in capture_fields if not frontmatter.get(f)]
    if missing_capture:
        fail(
            f"Type {type_path} requires capture field(s) {', '.join(missing_capture)} - pass them "
            "explicitly, e.g. --set fidelity=verbatim --set authority=reporting. "
            "new does not guess them (see raw/CONTRACT.md)."
        )
    guessed_unknown = [f for f in capture_fields if frontmatter.get(f) == "unknown"]
    if guessed_unknown:
        fail(
            f"Capture field(s) {', '.join(guessed_unknown)} cannot be set to 'unknown' here - that "
            "value is backfill-only, written only by `wikitool touch` on a page predating this rule."
        )

    target_dir = _target_dir(type_path, frontmatter)
    _type_spec, template = _load_type_or_fail(type_path, target_dir)
    _validate_or_fail(frontmatter, type_path, target_dir)

    if "raw_files" in frontmatter:
        check_raw_files_exist(frontmatter["raw_files"])

    path = target_dir / f"{page_title}.md"
    body = _apply_template_variables(
        template,
        {
            **frontmatter,
            "name": name,
            "today": today.isoformat(),
        },
    )

    write_page(path, frontmatter, body)
    success(f"Created {rel_path(path)}")