module vbugreport

import net.urllib
import os

const github_bug_issue_form_base_uri = 'https://github.com/vlang/v/issues/new?template=bug-report.yml'
const github_issue_form_url_soft_limit = 7500

pub struct BugReport {
    description  string
    reproduction string
    expected     string
    current      string
    solution     string
    context      string
    version      string
    environment  string
}

struct IssueFormField {
    name  string
    label string
    value string
}

pub enum BugReportDeliveryMode {
    github_form
    local_report
}

pub struct BugReportDelivery {
pub:
    mode              BugReportDeliveryMode
    uri               string
    local_report_path string
    local_report_body string
}

fn field_value_or_default(value string, default_value string) string {
    trimmed := value.trim_space()
    if trimmed.len == 0 {
        return default_value
    }
    return trimmed
}

fn fenced_block(language string, value string) string {
    content := field_value_or_default(value, 'N/A')
    return '```' + language + '\n' + content + '\n```'
}

fn quoted_command(file_path string, generated_file string, user_args string) string {
    mut compile_cmd := './vdbg'
    if user_args.len > 0 {
        compile_cmd += ' ${user_args}'
    }
    compile_cmd += ' ${os.quoted_path(file_path)}'
    return './v -g -o vdbg cmd/v && ${compile_cmd} && ${os.quoted_path(os.real_path(generated_file))}'
}

// new_bug_report builds the structured fields used by the GitHub bug report form.
pub fn new_bug_report(file_path string, generated_file string, user_args string, expected_result string, version string, vdoctor_output string, file_content string, build_output string) BugReport {
    command := quoted_command(file_path, generated_file, user_args)
    source_name := os.file_name(file_path)
    return BugReport{
        description:  'Running `${command}` on `${source_name}` produced a compiler error.'
        reproduction: '${fenced_block('sh', command)}\n\n${fenced_block('v', file_content)}'
        expected:     field_value_or_default(expected_result, 'N/A')
        current:      fenced_block('', build_output)
        solution:     '_No response_'
        context:      'Generated by `v bug` from `${file_path}`.'
        version:      field_value_or_default(version, 'N/A')
        environment:  fenced_block('', vdoctor_output)
    }
}

// issue_form_fields must stay aligned with `.github/ISSUE_TEMPLATE/bug-report.yml`.
fn issue_form_fields(report BugReport) []IssueFormField {
    return [
        IssueFormField{
            name:  'description'
            label: 'Describe the bug'
            value: report.description
        },
        IssueFormField{
            name:  'reproduction'
            label: 'Reproduction Steps'
            value: report.reproduction
        },
        IssueFormField{
            name:  'expected'
            label: 'Expected Behavior'
            value: report.expected
        },
        IssueFormField{
            name:  'current'
            label: 'Current Behavior'
            value: report.current
        },
        IssueFormField{
            name:  'solution'
            label: 'Possible Solution'
            value: report.solution
        },
        IssueFormField{
            name:  'context'
            label: 'Additional Information/Context'
            value: report.context
        },
        IssueFormField{
            name:  'version'
            label: 'V version'
            value: report.version
        },
        IssueFormField{
            name:  'environment'
            label: 'Environment details (OS name and version, etc.)'
            value: report.environment
        },
    ]
}

fn github_issue_form_uri(report BugReport) string {
    mut query_params := []string{}
    for field in issue_form_fields(report) {
        query_params << '${field.name}=${urllib.query_escape(field.value)}'
    }
    return '${github_bug_issue_form_base_uri}&${query_params.join('&')}'
}

fn bug_report_markdown(report BugReport) string {
    mut lines := [
        '# V Bug Report',
        '',
        'Generated by `v bug`.',
        '',
    ]
    for field in issue_form_fields(report) {
        lines << '### ${field.label}'
        lines << ''
        lines << field.value
        lines << ''
    }
    return lines.join('\n')
}

fn bug_report_file_path(file_path string) string {
    base_name := os.file_name(file_path)
    stem := if base_name.contains('.') { base_name.all_before_last('.') } else { base_name }
    file_name := if stem.len == 0 { 'v-bug-report.md' } else { '${stem}.bug-report.md' }
    file_dir := os.dir(file_path)
    return if file_dir.len == 0 || file_dir == '.' {
        file_name
    } else {
        os.join_path(file_dir, file_name)
    }
}

// prepare_bug_report_delivery chooses between a prefilled issue-form URL and a local markdown fallback.
pub fn prepare_bug_report_delivery(report BugReport, file_path string) BugReportDelivery {
    uri := github_issue_form_uri(report)
    if uri.len <= github_issue_form_url_soft_limit {
        return BugReportDelivery{
            mode: .github_form
            uri:  uri
        }
    }
    return BugReportDelivery{
        mode:              .local_report
        uri:               github_bug_issue_form_base_uri
        local_report_path: bug_report_file_path(file_path)
        local_report_body: bug_report_markdown(report)
    }
}