/**
 * Svelte Stage 2 — Generates stores from Stage 1 output.
 *
 * Subscribes to the kernel for state. Returns readable stores.
 */

function pascalCase(str) {
    return str.split(/[.\-_]/).map(p => p.charAt(0).toUpperCase() + p.slice(1)).join('')
}

export function generateSvelteAdapter(schema) {
    const functions = schema['x-mizan-functions'] || []
    const contextGroups = schema['x-mizan-contexts'] || {}
    const mutations = functions.filter(fn => !fn.isContext && !fn.isForm && fn.affects)
    const plainFns = functions.filter(fn => !fn.isContext && !fn.isForm && !fn.affects)

    const lines = [
        '// AUTO-GENERATED by mizan — do not edit',
        '',
        "import { readable, type Readable } from 'svelte/store'",
        "import { registerContext, type ContextState } from '@mizan/base'",
        '',
    ]

    const stage1Imports = []
    for (const [ctxName] of Object.entries(contextGroups)) {
        const p = pascalCase(ctxName)
        stage1Imports.push(`fetch${p}Context`, `type ${p}ContextData`, `type ${p}ContextParams`)
    }
    for (const fn of [...mutations, ...plainFns]) {
        stage1Imports.push(`call${pascalCase(fn.camelName)}`)
    }
    if (stage1Imports.length > 0) {
        lines.push(`import { ${stage1Imports.join(', ')} } from '../index'`)
        lines.push('')
    }

    for (const [ctxName, ctxMeta] of Object.entries(contextGroups)) {
        const p = pascalCase(ctxName)
        const ctxFunctions = functions.filter(fn => fn.isContext === ctxName)
        const paramEntries = Object.entries(ctxMeta.params || {})
        const paramsArg = paramEntries.length > 0 ? 'params' : '{} as any'

        if (paramEntries.length > 0) {
            lines.push(`export function create${p}Context(params: ${p}ContextParams) {`)
        } else {
            lines.push(`export function create${p}Context() {`)
        }

        // Use readable store backed by kernel subscription
        lines.push(`    const store = readable<ContextState<${p}ContextData>>(`)
        lines.push(`        { data: null, status: 'idle', error: null },`)
        lines.push(`        (set) => {`)
        lines.push(`            const handle = registerContext('${ctxName}', ${paramsArg}, () => fetch${p}Context(${paramsArg}))`)
        lines.push(`            const unsub = handle.subscribe(() => set(handle.getState()))`)
        lines.push(`            handle.refetch()`)
        lines.push(`            return () => { unsub(); handle.unregister() }`)
        lines.push(`        },`)
        lines.push(`    )`)
        lines.push('')
        lines.push(`    return store`)
        lines.push('}')
        lines.push('')
    }

    // Re-export mutations as-is from Stage 1
    for (const fn of [...mutations, ...plainFns]) {
        const p = pascalCase(fn.camelName)
        lines.push(`export { call${p} } from '../index'`)
    }
    lines.push('')

    lines.push("export type { ContextState } from '@mizan/base'")
    lines.push("export { configure, initSession, MizanError } from '@mizan/base'")
    lines.push('')

    return lines.join('\n')
}