#!/usr/bin/env python3
#
# (c) 2020 Lewin Bormann <lbo@spheniscida.de>
#
# Please let me know about your use case of this code!

import argparse
import chevron
import json
import re
import requests

from os import path

from templates import *


def optionalize(name, optional=True):
    return 'Option<{}>'.format(name) if optional else name


def replace_keywords(name):
    return {
        'type': ('typ', 'type'),
    }.get(name, name)


def capitalize_first(name):
    if len(name) == 0:
        return name
    return name[0].upper() + name[1:]


def snake_case(name):
    def r(c):
        if not c.isupper():
            return c
        return '_' + c.lower()

    return ''.join([(r(c) if i > 0 else c.lower()) for i, c in enumerate(name)])


def global_params_name(api_name):
    return capitalize_first(api_name) + 'Params'


def parse_schema_types(name, schema, optional=True):
    """Translate a JSON schema type into Rust types, recursively.

    This function takes a schema entry from the `schemas` section of a Discovery document,
    and generates all Rust structs needed to represent the schema, recursively.

    Arguments:
        name: Name of the property. If the property is an object with fixed fields, generate a struct with this name.
        schema: A JSON object from a discovery document representing a type.

    Returns:
        (tuple, [dict])

        where type is a tuple where the first element is a Rust type and the
        second element is a comment detailing the use of the field. The list of
        dicts returned as second element are any structs that need to be separately
        implemented and that the generated struct (if it was a struct) depends
        on. The dict contains elements as expected by templates.SchemaStructTmpl.
    """
    typ = ''
    comment = ''
    structs = []
    try:
        if '$ref' in schema:
            # We just assume that there is already a type generated for the reference.
            return optionalize(schema['$ref'], optional), structs
        if 'type' in schema and schema['type'] == 'object':
            # There are two types of objects: those with `properties` are translated into a Rust struct,
            # and those with `additionalProperties` into a HashMap<String, ...>.

            # Structs are represented as dicts that can be used to render the SchemaStructTmpl.
            if 'properties' in schema:
                typ = name
                struct = {'name': name, 'description': schema.get('description', ''), 'fields': []}
                for pn, pp in schema['properties'].items():
                    subtyp, substructs = parse_schema_types(name + capitalize_first(pn), pp, optional=True)
                    if type(subtyp) is tuple:
                        subtyp, comment = subtyp
                    else:
                        comment = None
                    cleaned_pn = replace_keywords(pn)
                    if type(cleaned_pn) is tuple:
                        jsonname = cleaned_pn[1]
                        cleaned_pn = snake_case(cleaned_pn[0])
                    else:
                        jsonname = pn
                        cleaned_pn = snake_case(cleaned_pn)
                    struct['fields'].append({
                        'name':
                        cleaned_pn,
                        'original_name':
                        jsonname,
                        'attr':
                        '#[serde(rename = "{}")]'.format(jsonname) +
                        '\n    #[serde(skip_serializing_if = "Option::is_none")]'
                        if subtyp.startswith('Option') else '',
                        'typ':
                        subtyp,
                        'comment':
                        comment
                    })
                    structs.extend(substructs)
                structs.append(struct)
                return (optionalize(typ, optional), schema.get('description', '')), structs

            if 'additionalProperties' in schema:
                field, substructs = parse_schema_types(name, schema['additionalProperties'], optional=False)
                structs.extend(substructs)
                if type(field) is tuple:
                    typ = field[0]
                else:
                    typ = field
                return (optionalize('HashMap<String,' + typ + '>', optional), schema.get('description', '')), structs

        if schema['type'] == 'array':
            typ, substructs = parse_schema_types(name, schema['items'], optional=False)
            if type(typ) is tuple:
                typ = typ[0]
            return (optionalize('Vec<' + typ + '>', optional), schema.get('description', '')), structs + substructs

        if schema['type'] == 'string':

            def build(intt, typ='String'):
                return (optionalize(typ, optional), intt + ': ' + schema.get('description', '')), structs

            if 'format' in schema:
                if schema['format'] == 'int64':
                    return build('i64')
                if schema['format'] == 'int32':
                    return build('i32')
                if schema['format'] == 'uint64':
                    return build('u64')
                if schema['format'] == 'uint32':
                    return build('u32')
                if schema['format'] == 'double':
                    return build('f64')
                if schema['format'] == 'float':
                    return build('f32')
                if schema['format'] == 'date-time':
                    return build('DateTime', typ='DateTime<Utc>')
            return (optionalize('String', optional), schema.get('description', '')), structs

        if schema['type'] == 'boolean':
            return (optionalize('bool', optional), schema.get('description', '')), structs

        if schema['type'] in ('number', 'integer'):

            def build(intt):
                return (optionalize(intt, optional), schema.get('description', '')), structs

            if schema['format'] == 'float':
                return build('f32')
            if schema['format'] == 'double':
                return build('f64')
            if schema['format'] == 'int32':
                return build('i32')
            if schema['format'] == 'int64':
                return build('i64')
            if schema['format'] == 'uint32':
                return build('u32')
            if schema['format'] == 'uint64':
                return build('u64')

        if schema['type'] == 'any':
            return (optionalize('String', optional), 'ANY data: ' + schema.get('description', '')), structs

        raise Exception('unimplemented schema type!', name, schema)
    except KeyError as e:
        print('KeyError while processing:', name, schema)
        raise e


def generate_params_structs(resources, super_name='', global_params=None):
    """Generate parameter structs from the resources list.

    Returns a list of source code strings.
    """
    frags = []
    for resourcename, resource in resources.items():
        for methodname, method in resource.get('methods', {}).items():
            param_type_name = capitalize_first(super_name) + capitalize_first(resourcename) + capitalize_first(
                methodname) + 'Params'
            print("processed:", resourcename, methodname, param_type_name)
            struct = {
                'name': param_type_name,
                'description': 'Parameters for the `{}.{}` method.'.format(resourcename, methodname),
                'fields': []
            }
            req_query_parameters = []
            opt_query_parameters = []
            struct['fields'].append({
                'name': snake_case(global_params),
                'typ': optionalize(global_params, True),
                'attr': '#[serde(flatten)]',
                'comment': 'General attributes applying to any API call'
            })
            # Build struct dict for rendering.
            if 'parameters' in method:
                for paramname, param in method['parameters'].items():
                    (typ, desc), substructs = parse_schema_types('', param, optional=False)
                    field = {
                        'name': snake_case(paramname),
                        'original_name': paramname,
                        'typ': optionalize(typ, not param.get('required', False)),
                        'comment': desc,
                        'attr': '#[serde(rename = "{}")]'.format(paramname),
                    }
                    struct['fields'].append(field)
                    if param.get('location', '') == 'query':
                        if param.get('required', False):
                            req_query_parameters.append(field)
                        else:
                            opt_query_parameters.append(field)
            frags.append(chevron.render(SchemaStructTmpl, struct))
            struct['required_fields'] = req_query_parameters
            struct['optional_fields'] = opt_query_parameters
            frags.append(chevron.render(SchemaDisplayTmpl, struct))
        # Generate parameter types for subresources.
        frags.extend(generate_params_structs(resource.get('resources', {}), super_name=resourcename))
    return frags


def resolve_parameters(string, paramsname='params', suffix=''):
    """Returns a Rust syntax for formatting the given string with API
    parameters, and a list of (snake-case) API parameters that are used. """
    pat = re.compile('\{(\w+)\}')
    params = re.findall(pat, string)
    snakeparams = [snake_case(p) for p in params]
    format_params = ','.join(['{}={}.{}{}'.format(p, paramsname, sp, suffix) for (p, sp) in zip(params, snakeparams)])
    # Some required parameters are in the URL. This rust syntax formats the relative URL part appropriately.
    return 'format!("{}", {})'.format(string, format_params), snakeparams


def generate_service(resource, methods, discdoc):
    """Generate the code for all methods in a resource.

    Returns a rendered string with source code.
    """
    service = capitalize_first(resource)
    # Source code fragments implementing the methods.
    method_fragments = []
    # Source code fragments for impls of subordinate resources.
    subresource_fragments = []

    # Generate methods for subresources.
    for subresname, subresource in methods.get('resources', {}).items():
        subresource_fragments.append(generate_service(service + capitalize_first(subresname), subresource, discdoc))

    for methodname, method in methods.get('methods', {}).items():
        # Goal: Instantiate the templates for upload and non-upload methods.

        # e.g. FilesGetParams
        params_type_name = service + capitalize_first(methodname) + 'Params'
        # All parameters that are optional (as URL parameters)
        parameters = {
            p: snake_case(p)
            for p, pp in method.get('parameters', {}).items() if ('required' not in pp and pp['location'] != 'path')
        }
        # All required parameters not represented in the path.
        required_parameters = {
            p: snake_case(p)
            for p, pp in method.get('parameters', {}).items() if ('required' in pp and pp['location'] != 'path')
        }
        # Types of the function
        in_type = method['request']['$ref'] if 'request' in method else '()'
        out_type = method['response']['$ref'] if 'response' in method else '()'

        is_download = method.get('supportsMediaDownload', False) and not method.get('useMediaDownloadService', False)
        is_upload = 'mediaUpload' in method

        media_upload = method.get('mediaUpload', None)
        if media_upload and 'simple' in media_upload['protocols']:
            upload_path = media_upload['protocols']['simple']['path']
        else:
            upload_path = ''
        http_method = method['httpMethod']
        has_global_params = 'parameters' in discdoc
        formatted_path, required_params = resolve_parameters(method['path'])

        if is_download:
            assert out_type == '()'
            data_download = {
                'name': snake_case(methodname),
                'param_type': params_type_name,
                'in_type': in_type,
                'out_type': out_type,
                'base_path': discdoc['baseUrl'],
                'rel_path_expr': formatted_path,
                'params': [{
                    'param': p,
                    'snake_param': sp
                } for (p, sp) in parameters.items()],
                'required_params': [{
                    'param': p,
                    'snake_param': sp
                } for (p, sp) in required_parameters.items()],
                'global_params_name':
                snake_case(global_params_name(discdoc.get('name', ''))) if has_global_params else None,
                'scopes': [{
                    'scope': method.get('scopes', [''])[-1]
                }],
                'description': method.get('description', ''),
                'http_method': http_method
            }
            if in_type == '()':
                data_download.pop('in_type')
            method_fragments.append(chevron.render(DownloadMethodTmpl, data_download))
        else:
            data_normal = {
                'name': snake_case(methodname),
                'param_type': params_type_name,
                'in_type': in_type,
                'out_type': out_type,
                'base_path': discdoc['baseUrl'],
                'rel_path_expr': formatted_path,
                'params': [{
                    'param': p,
                    'snake_param': sp
                } for (p, sp) in parameters.items()],
                'global_params_name':
                snake_case(global_params_name(discdoc.get('name', ''))) if has_global_params else None,
                'required_params': [{
                    'param': p,
                    'snake_param': sp
                } for (p, sp) in required_parameters.items()],
                'scopes': [{
                    'scope': method.get('scopes', [''])[-1]
                }],
                'description': method.get('description', ''),
                'http_method': http_method
            }
            if in_type == '()':
                data_normal.pop('in_type')
            method_fragments.append(chevron.render(NormalMethodTmpl, data_normal))

            # We generate an additional implementation with the option of uploading data.
            if is_upload:
                data_upload = {
                    'name': snake_case(methodname),
                    'param_type': params_type_name,
                    'in_type': in_type,
                    'out_type': out_type,
                    'base_path': discdoc['rootUrl'],
                    'rel_path_expr': '"' + upload_path.lstrip('/') + '"',
                    'global_params_name':
                    snake_case(global_params_name(discdoc.get('name', ''))) if has_global_params else None,
                    'params': [{
                        'param': p,
                        'snake_param': sp
                    } for (p, sp) in parameters.items()],
                    'required_params': [{
                        'param': p,
                        'snake_param': sp
                    } for (p, sp) in required_parameters.items()],
                    'scopes': [{
                        'scope': method.get('scopes', [''])[-1]
                    }],
                    'description': method.get('description', ''),
                    'http_method': http_method,
                }
                method_fragments.append(chevron.render(UploadMethodTmpl, data_upload))

    return chevron.render(
        ServiceImplementationTmpl, {
            'service': service,
            'name': capitalize_first(discdoc.get('name', '')),
            'methods': [{
                'text': t
            } for t in method_fragments]
        }) + '\n'.join(subresource_fragments)


def generate_scopes_type(name, scopes):
    """Generate types for the `scopes` dictionary (path: auth.oauth2.scopes in a discovery document),
    containing { scope_url: { description: "..." } }.
    """
    name = capitalize_first(name)
    if len(scopes) == 0:
        return chevron.render(OauthScopesType, {'name': name, 'scopes': []})
    parameters = {'name': name, 'scopes': []}
    for url, desc in scopes.items():
        rawname = url.split('/')[-1]
        fancy_name = ''.join([capitalize_first(p) for p in rawname.split('.')]).replace('-', '')
        parameters['scopes'].append({'scope_name': fancy_name, 'desc': desc.get('description', ''), 'url': url})
    return chevron.render(OauthScopesType, parameters)


def generate_all(discdoc):
    """Generate all structs and impls, and render them into a file."""
    print('Processing:', discdoc.get('id', ''))
    schemas = discdoc.get('schemas', {})
    resources = discdoc.get('resources', {})
    # Generate scopes.
    scopes_type = generate_scopes_type(discdoc['name'], discdoc.get('auth', {}).get('oauth2', {}).get('scopes', {}))

    # Generate parameter types (*Params - those are used as "side inputs" to requests)
    params_struct_name = capitalize_first(discdoc['name']) + 'Params'
    parameter_types = generate_params_structs(resources, global_params=params_struct_name)

    # Generate service impls.
    services = []
    for resource, methods in resources.items():
        services.append(generate_service(resource, methods, discdoc))

    # Generate schema types.
    structs = []
    for name, desc in schemas.items():
        typ, substructs = parse_schema_types(name, desc)
        structs.extend(substructs)

    # Generate global parameters struct and its Display impl.
    if 'parameters' in discdoc:
        schema = {'type': 'object', 'properties': discdoc['parameters']}
        name = params_struct_name
        typ, substructs = parse_schema_types(name, schema)
        for s in substructs:
            s['optional_fields'] = s['fields']
            parameter_types.append(chevron.render(SchemaDisplayTmpl, s))
        structs.extend(substructs)

    # Assemble everything into a file.
    modname = (discdoc['id'] + '_types').replace(':', '_')
    with open(path.join('gen', modname + '.rs'), 'w') as f:
        f.write(RustHeader)
        f.write(scopes_type)
        # Render resource structs.
        for s in structs:
            for field in s['fields']:
                if field.get('comment', None):
                    field['comment'] = field['comment'].replace('\n', ' ')
            if not s['name']:
                print('WARN', s)
            f.write(chevron.render(SchemaStructTmpl, s))
        # Render *Params structs.
        for pt in parameter_types:
            f.write(pt)
        # Render service impls.
        for s in services:
            f.write(s)


def fetch_discovery_base(url, apis):
    """Fetch the discovery base document from `url`. Return api documents for APIs with IDs in `apis`.

    Returns:
        List of API JSON documents.
    """
    doc = json.loads(requests.get(url).text)
    return [it for it in doc['items'] if (not apis or it['id'] in apis)]


def fetch_discovery_doc(api_doc):
    """Fetch discovery document for a given (short) API doc from the overall discovery document."""
    url = api_doc['discoveryRestUrl']
    return json.loads(requests.get(url).text)


def main():
    p = argparse.ArgumentParser(description='Generate Rust code for asynchronous REST Google APIs.')
    p.add_argument('--discovery_base',
                   default='https://www.googleapis.com/discovery/v1/apis',
                   help='Base Discovery document.')
    p.add_argument('--only_apis', default='drive:v3', help='Only process APIs with these IDs (comma-separated)')
    args = p.parse_args()
    if args.only_apis:
        apilist = args.only_apis.split(',')
    else:
        apilist = []

    docs = fetch_discovery_base(args.discovery_base, apilist)
    for doc in docs:
        try:
            discdoc = fetch_discovery_doc(doc)
            if 'error' in discdoc:
                print('Error while fetching document for', doc['id'], ':', discdoc)
                continue
            generate_all(discdoc)
        except Exception as e:
            print("Error while processing", discdoc)
            print(e)
            continue


if __name__ == '__main__':
    main()