package PAGI::FastAPI::Context;

use v5.38;
use experimental 'class';
use version;

our $VERSION   = qv('v1.2.2');
our $AUTHORITY = 'cpan:MANWAR';

class PAGI::FastAPI::Context {
    use Future::IO;

    field $scope        :param = {};
    field $query_params :param = {};
    field $path_params  :param = {};
    field $body         :param = undef;
    field $status       :param = 200;
    field $res_headers  :param = [];
    field $stash        :param = {};
    field $pagi_context :param = undef;

    method scope { $scope }

    method sleep ($seconds) {
        return Future::IO->sleep($seconds);
    }

    method status ($val = undef) {
        if (defined $val) {
            $status = $val;
        }
        return $status;
    }

    method pagi_context { $pagi_context }

    method csrf_token () {
        # 1. Direct scope environment
        if (defined $scope
            && ref $scope eq 'HASH'
            && $scope->{'pagi.csrf_token'}) {
            return $scope->{'pagi.csrf_token'};
        }

        # 2. PAGI context environment
        if (defined $pagi_context
            && $pagi_context->can('env')) {
            my $env = $pagi_context->env;
            return $env->{'pagi.csrf_token'}
                if $env && $env->{'pagi.csrf_token'};
        }

        # 3. Session storage fallback
        if (defined $scope
            && $scope->{'pagi.session'}
            && ref $scope->{'pagi.session'} eq 'HASH') {
            return $scope->{'pagi.session'}{'csrf_token'};
        }

        return undef;
    }

    method csrf_verify ($token) {
        die "PAGI context is not set" unless defined $pagi_context;
        return $pagi_context->csrf_verify($token);
    }

    method res_headers { $res_headers }

    method set_header ($key, $val) {
        my $lc_key = lc($key);
        for my $h (@$res_headers) {
            if (lc($h->[0]) eq $lc_key) {
                $h->[0] = $key;
                $h->[1] = $val;
                return;
            }
        }
        push @$res_headers, [$key, $val];
    }

    method add_header ($key, $val) {
        push @$res_headers, [$key, $val];
    }

    method header ($name) {
        my $headers = $scope->{headers} // [];
        my $lc_name = lc($name);
        for my $h (@$headers) {
            return $h->[1] if lc($h->[0]) eq $lc_name;
        }
        return undef;
    }

    method html ($content, %opts) {
        use PAGI::FastAPI::Response::HTML;

        return PAGI::FastAPI::Response::HTML->new(
            body    => $content,
            headers => $opts{headers} // [],
            status  => $opts{status}  // 200,
        );
    }

    method sse ($code) {
        use PAGI::FastAPI::Response::SSE;

        return PAGI::FastAPI::Response::SSE->new(
            generator => $code,
        );
    }

    method path_params  { $path_params }
    method query_params { $query_params }

    method path_param ($name) {
        return $path_params->{$name};
    }

    method query_param ($name) {
        return $query_params->{$name};
    }

    method body ($key = undef) {
        if (defined $key) {
            return (ref $body eq 'HASH') ? $body->{$key} : undef;
        }
        return $body;
    }

    method param ($key) {
        return $self->path_param($key)
            // $self->query_param($key)
            // $self->body($key);
    }

    method stash { $stash }
}

=encoding utf-8

=head1 NAME

PAGI::FastAPI::Context - Request and Response Lifecycle Context for PAGI::FastAPI

=head1 VERSION

Version v1.2.2

=head1 SYNOPSIS

    # Inspecting Request Parameters
    my $user_id = $c->path_param('id');
    my $limit   = $c->query_param('limit');
    my $name    = $c->body('name');

    # Generic Parameter Fallback (Path -> Query -> Body)
    my $token   = $c->param('token');

    # Headers & Scope
    my $ua      = $c->header('User-Agent');
    my $scope   = $c->scope;

    # Stash Storage
    $c->stash->{user} = { id => 42, role => 'admin' };

    # Modifying Response State
    $c->status(201);
    $c->set_header('X-Custom-Header' => 'value');

=head1 DESCRIPTION

C<PAGI::FastAPI::Context> encapsulates the request environment, parsed parameters,
payload data, and response state for an individual HTTP exchange processed
by L<PAGI::FastAPI>.

An instance of this context is passed as the primary argument to route handlers,
middleware functions, and dependency blocks.

=head1 METHODS

=head2 C<new(%args)>

Constructor called internally by L<PAGI::FastAPI>. Accepts named arguments:

=over 4

=item * C<scope> - PAGI environment HashRef.

=item * C<query_params> - HashRef of validated query parameters.

=item * C<path_params> - HashRef of route path variables.

=item * C<body> - Decoded payload body (HashRef, ArrayRef, or Scalar).

=item * C<status> - Initial HTTP response code (default: C<200>).

=item * C<res_headers> - Initial response headers ArrayRef (default: C<[]>).

=item * C<stash> - Context-bound storage HashRef (default: C<{}>).

=back

=head2 C<scope()>

Returns the raw PAGI scope HashRef for the current request.

=head2 C<sleep($seconds)>

    await $c->sleep(1);

Asynchronously pauses execution for the given number of seconds without blocking the event loop.

Uses L<Future::IO> under the hood to ensure non-blocking sleep operations.

=over 4

=item * C<$seconds>

Number of seconds to sleep (fractional seconds like C<0.5> are supported).

=back

Returns a L<Future> that completes when the specified sleep duration has elapsed.

=head2 C<status([ $code ])>

Gets or sets the HTTP status code for the response.

    $c->status(403);
    my $code = $c->status; # 403

=head2 C<pagi_context>

    my $pagi_ctx = $c->pagi_context;

Returns the underlying low-level L<PAGI::Context> instance associated with
the current HTTP request. Useful for low-level protocol inspection, raw
environment access, or invoking protocol-specific extension methods.

=head2 C<csrf_token>

    my $token = $c->csrf_token;

Retrieves the active Anti-CSRF token for the current request.

This method transparently attempts to resolve the token from three potential
locations in order of precedence:

=over 4

=item 1. B<Direct Scope Environment:> C<< $scope->{'pagi.csrf_token'} >> (set directly by L<PAGI::Middleware::CSRF>).

=item 2. B<PAGI Context Environment:> C<< $pagi_context->env->{'pagi.csrf_token'} >>.

=item 3. B<Session Storage Fallback:> C<< $scope->{'pagi.session'}{'csrf_token'} >> (set by session management middleware).

=back

Returns the scalar token string if found, or C<undef> if no token is
available or if CSRF/Session middleware is not active for the request.

B<Example Usage (Embedding in HTML forms):>

    $app->get('/form', handler => async sub ($c) {
        my $token = $c->csrf_token // '';
        return $c->html(qq{
            <form method="POST" action="/submit">
                <input type="hidden" name="csrf_token" value="$token">
                <button type="submit">Submit</button>
            </form>
        });
    });

=head2 C<csrf_verify($token)>

    my $is_valid = $c->csrf_verify($submitted_token);

Explicitly validates the given C<$token> against the current request's CSRF
state by delegating to the underlying low-level L<PAGI::Context> instance.

Accepts a scalar token string C<$token>. Returns a true value if the token
signature and expiration are valid; returns false otherwise.

Dies with C<"PAGI context is not set"> if invoked when no low-level
L<PAGI::Context> instance is associated with C<$c>.

B<Example Usage (Manual Verification):>

    $app->post('/api/action', handler => async sub ($c) {
        my $token = $c->body('csrf_token');

        unless ($c->csrf_verify($token)) {
            $c->status(403);
            return { error => 'Invalid or missing CSRF token' };
        }

        return { status => 'success' };
    });

=head2 C<res_headers()>

Returns the current list of outgoing response header pairs as an ArrayRef of
tuple pairs C<[ [$name, $val], ... ]>.

=head2 C<set_header($key, $val)>

Sets an outgoing HTTP header, case-insensitively replacing any existing
header of the same name (last write wins). Use this for headers that
should only ever have one value.

    $c->set_header('X-Frame-Options' => 'DENY');
    $c->set_header('Content-Type'    => 'text/plain'); # replaces any prior Content-Type

=head2 C<add_header($key, $val)>

Appends an additional outgoing HTTP header pair without touching any
existing header of the same name. Use this only for headers that are
legitimately allowed to appear more than once (e.g. C<Set-Cookie>,
C<Vary>, C<Link>); for everything else prefer C<set_header>.

    $c->add_header('Set-Cookie' => 'session=abc123; Path=/');
    $c->add_header('Set-Cookie' => 'theme=dark; Path=/');

=head2 C<header($name)>

Case-insensitively searches incoming request headers (from C<< $c->scope->{headers} >>)
and returns its scalar value, or C<undef> if missing.

    my $auth = $c->header('Authorization');

=head2 C<html($content, %options)>

    $app->get('/about', handler => async sub ($c) {
        return $c->html('<h1>About Us</h1>');
    });

Returns an HTTP response with the C<Content-Type> header automatically set to C<text/html; charset=utf-8>.

Accepts the HTML content string as the first parameter, followed by optional named parameters:

=over 4

=item * C<status> (Optional)

Integer HTTP status code. Defaults to C<200>.

=item * C<headers> (Optional)

ArrayRef of additional header key-value pairs.

=back

Returns a C<PAGI::FastAPI::Response> object.

=head2 C<sse($code)>

    $app->get('/api/v1/metrics', handler => async sub ($c) {
        return $c->sse(async sub ($stream) {
            while (1) {
                await $stream->send_json({ cpu => 42 });
                await $c->sleep(1);
            }
        });
    });

Creates and returns a Server-Sent Events (SSE) response object.

Accepts an async generator coderef that receives an SSE stream handler as
its first argument.

=over 4

=item * C<$code>

An C<async sub> coderef that defines the event streaming loop. The callback
receives an instance of L<PAGI::SSE>, offering methods such as
C<send_event()>, C<send_json()>, C<send()>, C<keepalive()>, and C<close()>.

=back

Returns an instance of L<PAGI::FastAPI::Response::SSE>.

=head2 C<path_params()>

Returns the HashRef containing all parsed path parameters.

=head2 C<path_param($key)>

Returns a specific parsed path parameter by name, or C<undef> if absent.

=head2 C<query_params()>

Returns the HashRef containing all parsed query parameters.

=head2 C<query_param($key)>

Returns a specific parsed query parameter by name, or C<undef> if absent.

=head2 C<body([ $key ])>

If called without parameters, returns the full raw/decoded request body.

If called with a C<$key> parameter and the body is a HashRef, returns the
value for that key, or C<undef> if missing or if the body is not a HashRef.

    my $full_body = $c->body;
    my $user_name = $c->body('username');

=head2 C<param($key)>

Convenience parameter accessor that checks parameter stores in priority order:

1. Path parameters (C<path_param>)
2. Query parameters (C<query_param>)
3. JSON/Body fields (C<body($key)>)

Returns the first matching non-undef value, or C<undef> if the key is not
present in any store.

=head2 C<stash()>

Returns a HashRef tied to the lifecycle of this context. Useful for sharing
data between middleware, dependency injection blocks, and final route
handlers.

    $c->stash->{db_session} = $db;

=head1 AUTHOR

Mohammad Sajid Anwar, C<< <mohammad.anwar at yahoo.com> >>

=head1 REPOSITORY

L<https://github.com/manwar/PAGI-FastAPI>

=head1 BUGS

Please report any bugs or feature requests through the web interface at L<https://github.com/manwar/PAGI-FastAPI/issues>.
I will be notified and then you'll automatically be notified of progress on your
bug as I make changes.

=head1 SUPPORT

You can find documentation for this module with the perldoc command.

    perldoc PAGI::FastAPI::Context

You can also look for information at:

=over 4

=item * BUG Report

L<https://github.com/manwar/PAGI-FastAPI/issues>

=item * Search MetaCPAN

L<https://metacpan.org/dist/PAGI-FastAPI/>

=back

=head1 LICENSE AND COPYRIGHT

Copyright (C) 2026 Mohammad Sajid Anwar.

This program is free software; you can redistribute it and/or modify it under
the terms of the Artistic License (2.0).

=cut

1; # End of PAGI::FastAPI::Context
