from __future__ import annotations

import csv
from enum import StrEnum
from pathlib import Path
from typing import Iterable

from pydantic import BaseModel, ConfigDict, Field

from .field_values import ignored_entry_field_overrides
from .models import AttachmentConfig, CampaignConfig, EntryConfig, SourceType


class Severity(StrEnum):
    INFO = "info"
    WARNING = "warning"
    ERROR = "error"


class SemanticIssue(BaseModel):
    model_config = ConfigDict(extra="forbid")

    severity: Severity
    code: str
    message: str
    path: str | None = None


class SemanticReport(BaseModel):
    model_config = ConfigDict(extra="forbid")

    campaign_id: str
    campaign_name: str
    issues: list[SemanticIssue] = Field(default_factory=list)
    entries_mode: str
    entries_count: int | None = None
    attachments_base_path: str
    rate_limit: str
    imap_append_enabled: bool

    @property
    def error_count(self) -> int:
        return sum(1 for issue in self.issues if issue.severity == Severity.ERROR)

    @property
    def warning_count(self) -> int:
        return sum(1 for issue in self.issues if issue.severity == Severity.WARNING)

    @property
    def ok(self) -> bool:
        return self.error_count == 0


def _issue(severity: Severity, code: str, message: str, path: str | None = None) -> SemanticIssue:
    return SemanticIssue(severity=severity, code=code, message=message, path=path)


def _resolve(campaign_file: Path, raw_path: str) -> Path:
    path = Path(raw_path).expanduser()
    if path.is_absolute():
        return path
    return (campaign_file.parent / path).resolve()


def _mapping_target_field_name(target: str) -> str | None:
    if target.startswith("fields."):
        return target.split(".", 1)[1]
    return None


def _mapping_target_known(target: str, field_names: set[str]) -> bool:
    direct_targets = {
        "id",
        "active",
        "last_sent",
        "combine_to",
        "combine_cc",
        "combine_bcc",
        "combine_reply_to",
        "combine_bounce_to",
        "combine_disposition_notification_to",
        "combine_attachments",
    }
    if target in direct_targets:
        return True
    if target.startswith("fields."):
        name = target.split(".", 1)[1]
        return not field_names or name in field_names
    if target.startswith("from."):
        return target in {"from.email", "from.name", "from.type"}
    for prefix in ["to", "cc", "bcc", "reply_to", "bounce_to", "disposition_notification_to"]:
        if target.startswith(prefix + "."):
            parts = target.split(".")
            return len(parts) == 3 and parts[1].isdigit() and parts[2] in {"email", "name", "type"}
    if target.startswith("attachments."):
        parts = target.split(".")
        # attachments.0.zip.filename_template etc.
        if len(parts) >= 3 and parts[1].isdigit():
            if parts[2] in {
                "id",
                "label",
                "base_dir",
                "file_filter",
                "include_subdirs",
                "required",
                "allow_multiple",
                "missing_behavior",
                "ambiguous_behavior",
            }:
                return len(parts) == 3
            if parts[2] == "zip" and len(parts) == 4:
                return parts[3] in {"enabled", "filename_template", "password_template", "method"}
    return False


def _csv_header(path: Path, delimiter: str, encoding: str) -> list[str] | None:
    with path.open("r", encoding=encoding, newline="") as handle:
        reader = csv.reader(handle, delimiter=delimiter)
        try:
            return next(reader)
        except StopIteration:
            return []


def _iter_template_source_paths(config: CampaignConfig) -> Iterable[tuple[str, str]]:
    if not config.template.source:
        return []
    source = config.template.source
    paths: list[tuple[str, str]] = []
    if source.subject_path:
        paths.append(("/template/source/subject_path", source.subject_path))
    if source.text_path:
        paths.append(("/template/source/text_path", source.text_path))
    if source.html_path:
        paths.append(("/template/source/html_path", source.html_path))
    return paths


def _attachment_base_path_report_value(config: CampaignConfig) -> str:
    if config.attachments.base_paths:
        return ", ".join(f"{base_path.name}: {base_path.path}" for base_path in config.attachments.base_paths)
    return config.attachments.base_path


def _iter_attachment_rules(config: CampaignConfig) -> Iterable[tuple[str, AttachmentConfig, bool]]:
    for index, attachment_config in enumerate(config.attachments.global_):
        yield f"/attachments/global/{index}", attachment_config, False

    inline_entries = config.entries.inline or [] if config.entries.is_inline else []
    for entry_index, entry in enumerate(inline_entries):
        for attachment_index, attachment_config in enumerate(entry.attachments):
            yield f"/entries/inline/{entry_index}/attachments/{attachment_index}", attachment_config, True

    if config.entries.defaults:
        for attachment_index, attachment_config in enumerate(config.entries.defaults.attachments):
            yield f"/entries/defaults/attachments/{attachment_index}", attachment_config, True


def _attachment_path_issues(config: CampaignConfig) -> list[SemanticIssue]:
    issues: list[SemanticIssue] = []
    configured_paths = {base_path.path for base_path in config.attachments.base_paths}
    individual_paths = config.attachments.individual_base_path_values

    if config.attachments.base_paths:
        for index, base_path in enumerate(config.attachments.base_paths):
            if not base_path.name.strip():
                issues.append(_issue(Severity.WARNING, "attachment_base_path_missing_name", "attachment base path has no display name", f"/attachments/base_paths/{index}/name"))
            if not base_path.path.strip():
                issues.append(_issue(Severity.ERROR, "attachment_base_path_missing_path", "attachment base path has no path", f"/attachments/base_paths/{index}/path"))
    elif not config.attachments.base_path:
        issues.append(_issue(Severity.INFO, "missing_attachment_base_path", "Attachment base path is not configured yet.", "/attachments/base_path"))

    if configured_paths:
        for path, attachment_config, is_individual in _iter_attachment_rules(config):
            if attachment_config.base_dir and attachment_config.base_dir not in configured_paths:
                issues.append(_issue(
                    Severity.WARNING,
                    "unknown_attachment_base_path",
                    f"attachment rule refers to base path {attachment_config.base_dir!r}, but it is not listed in attachments.base_paths",
                    f"{path}/base_dir",
                ))
            if is_individual and individual_paths and attachment_config.base_dir not in individual_paths:
                issues.append(_issue(
                    Severity.WARNING,
                    "individual_attachment_base_path_not_allowed",
                    f"individual attachment rule uses base path {attachment_config.base_dir!r}, but that base path does not allow individual attachments",
                    f"{path}/base_dir",
                ))
    return issues


def _ignored_override_issues(config: CampaignConfig, entry: EntryConfig, path_prefix: str) -> list[SemanticIssue]:
    return [
        _issue(
            Severity.WARNING,
            "field_override_not_allowed",
            f"recipient value for field {field_name!r} will be ignored because the field does not allow overrides",
            f"{path_prefix}/fields/{field_name}",
        )
        for field_name in ignored_entry_field_overrides(config, entry)
    ]


def validate_campaign_config(
    config: CampaignConfig,
    *,
    campaign_file: str | Path | None = None,
    check_files: bool = False,
) -> SemanticReport:
    campaign_path = Path(campaign_file).resolve() if campaign_file else Path.cwd() / "campaign.json"
    issues: list[SemanticIssue] = []

    field_names = config.field_names
    field_definitions = {field.name: field for field in config.fields}
    declared_names = set(field_definitions)

    for key in config.global_values:
        if declared_names and key not in declared_names:
            issues.append(_issue(
                Severity.WARNING,
                "unknown_global_value",
                f"global_values contains {key!r}, but it is not declared in fields",
                f"/global_values/{key}",
            ))

    issues.extend(_attachment_path_issues(config))

    if config.server.imap and config.server.imap.enabled:
        missing = [name for name in ["host", "port", "username", "password"] if getattr(config.server.imap, name) in (None, "")]
        if missing:
            issues.append(_issue(
                Severity.ERROR,
                "incomplete_imap_config",
                "IMAP append is enabled, but these IMAP settings are missing: " + ", ".join(missing),
                "/server/imap",
            ))

    if config.delivery.imap_append_sent.enabled and not (config.server.imap and config.server.imap.enabled):
        issues.append(_issue(
            Severity.WARNING,
            "delivery_imap_enabled_without_server_imap",
            "delivery.imap_append_sent is enabled, but server.imap.enabled is not true",
            "/delivery/imap_append_sent/enabled",
        ))

    if config.campaign.mode == "send" and not config.server.smtp:
        issues.append(_issue(
            Severity.ERROR,
            "missing_smtp_config",
            "campaign mode is 'send', but no server.smtp configuration is present",
            "/server/smtp",
        ))

    if config.server.smtp:
        missing = [name for name in ["host", "port"] if getattr(config.server.smtp, name) in (None, "")]
        if missing:
            issues.append(_issue(
                Severity.WARNING,
                "incomplete_smtp_config",
                "SMTP settings are present, but these settings are missing: " + ", ".join(missing),
                "/server/smtp",
            ))

    if config.entries.is_inline:
        inline_entries = config.entries.inline or []
        entries_count = len(inline_entries)
        entries_mode = "inline"
        if entries_count == 0:
            issues.append(_issue(Severity.WARNING, "no_inline_entries", "entries.inline is empty", "/entries/inline"))
        for index, entry in enumerate(inline_entries):
            issues.extend(_ignored_override_issues(config, entry, f"/entries/inline/{index}"))
    else:
        entries_count = None
        entries_mode = f"external:{config.entries.source.type.value if config.entries.source else 'unknown'}"
        mapping = config.entries.mapping or {}
        if not mapping:
            issues.append(_issue(Severity.ERROR, "empty_mapping", "external entries require a non-empty mapping", "/entries/mapping"))
        for target in mapping:
            if not _mapping_target_known(target, field_names):
                issues.append(_issue(
                    Severity.WARNING,
                    "unknown_mapping_target",
                    f"mapping target {target!r} is not recognized by the current campaign model",
                    f"/entries/mapping/{target}",
                ))
            field_name = _mapping_target_field_name(target)
            if field_name and field_name in field_definitions and not field_definitions[field_name].can_override:
                issues.append(_issue(
                    Severity.WARNING,
                    "mapping_target_not_overridable",
                    f"mapping target {target!r} points to a field that does not allow recipient overrides; mapped values will be ignored",
                    f"/entries/mapping/{target}",
                ))
        if config.entries.defaults:
            issues.extend(_ignored_override_issues(config, config.entries.defaults, "/entries/defaults"))
        if check_files and config.entries.source:
            source_path = _resolve(campaign_path, config.entries.source.path)
            if not source_path.exists():
                issues.append(_issue(
                    Severity.ERROR,
                    "entries_source_not_found",
                    f"entries source file does not exist: {source_path}",
                    "/entries/source/path",
                ))
            elif config.entries.source.type == SourceType.CSV and config.entries.source.has_header:
                try:
                    header = _csv_header(source_path, config.entries.source.delimiter, config.entries.source.encoding)
                    header_set = set(header or [])
                    missing_columns = sorted({source_name for source_name in mapping.values() if source_name not in header_set})
                    if missing_columns:
                        issues.append(_issue(
                            Severity.ERROR,
                            "mapping_columns_missing",
                            "CSV mapping refers to missing columns: " + ", ".join(missing_columns),
                            "/entries/mapping",
                        ))
                except OSError as exc:
                    issues.append(_issue(Severity.ERROR, "entries_source_read_error", str(exc), "/entries/source/path"))

    if check_files:
        if config.attachments.base_paths:
            for index, base_path_config in enumerate(config.attachments.base_paths):
                attachments_base_path = _resolve(campaign_path, base_path_config.path)
                if not attachments_base_path.exists():
                    issues.append(_issue(
                        Severity.WARNING,
                        "attachments_base_path_not_found",
                        f"attachment base path {base_path_config.name!r} does not exist: {attachments_base_path}",
                        f"/attachments/base_paths/{index}/path",
                    ))
        else:
            attachments_base_path = _resolve(campaign_path, config.attachments.base_path)
            if not attachments_base_path.exists():
                issues.append(_issue(
                    Severity.WARNING,
                    "attachments_base_path_not_found",
                    f"attachments.base_path does not exist: {attachments_base_path}",
                    "/attachments/base_path",
                ))
        for schema_path, raw_path in _iter_template_source_paths(config):
            path = _resolve(campaign_path, raw_path)
            if not path.exists():
                issues.append(_issue(
                    Severity.ERROR,
                    "template_source_not_found",
                    f"template source file does not exist: {path}",
                    schema_path,
                ))

    report = SemanticReport(
        campaign_id=config.campaign.id,
        campaign_name=config.campaign.name,
        issues=issues,
        entries_mode=entries_mode,
        entries_count=entries_count,
        attachments_base_path=_attachment_base_path_report_value(config),
        rate_limit=f"{config.delivery.rate_limit.messages_per_minute}/min, concurrency {config.delivery.rate_limit.concurrency}",
        imap_append_enabled=config.delivery.imap_append_sent.enabled,
    )
    return report