import {EscapeValue, QuerySafeValue, raw, SQLDialect} from './SQLDialect';
import {Constraint, isConstraintGroup, isConstraintItem, SpecifiedField} from "../types";
import {AbstractBuilder} from "../builder/AbstractBuilder";

/**
 * An implementation of the SQLDialect specific to PostgreSQL.
 */
export class PostgreSQLDialect extends SQLDialect {

    public escape(value: EscapeValue): QuerySafeValue {
        if ( value instanceof QuerySafeValue ) return value
        else if ( Array.isArray(value) ) {
            return new QuerySafeValue(value, `(${value.map(v => this.escape(v)).join(',')})`)
        } else if ( String(value).toLowerCase() === 'true' || value === true ) {
            return new QuerySafeValue(value, 'TRUE')
        } else if ( String(value).toLowerCase() === 'false' || value === false ) {
            return new QuerySafeValue(value, 'FALSE')
        } else if ( typeof value === 'number' ) {
            return new QuerySafeValue(value, `${value}`)
        } else if ( value instanceof Date ) {
            const pad = (val: number) => val < 10 ? `0${val}` : `${val}`
            const [y, m, d, h, i, s] = [
                `${value.getFullYear()}`,
                `${pad(value.getMonth() + 1)}`,
                `${pad(value.getDate())}`,
                `${pad(value.getHours())}`,
                `${pad(value.getMinutes())}`,
                `${pad(value.getSeconds())}`,
            ]

            return new QuerySafeValue(value, `${y}-${m}-${d} ${h}:${i}:${s}`)
        } else if ( !isNaN(Number(value)) ) {
            return new QuerySafeValue(value, String(Number(value)))
        } else if ( value === null || typeof value === 'undefined' ) {
            return new QuerySafeValue(value, 'NULL')
        } else {
            const escaped = value.replace(/'/g, '\\\'')  //.replace(/"/g, '\\"').replace(/`/g, '\\`')
            return new QuerySafeValue(value, `'${escaped}'`)
        }
    }

    public renderCount(query: string): string {
        return [
            'SELECT COUNT(*) AS "extollo_render_count"',
            'FROM (',
            ...query.split('\n').map(x => `  ${x}`),
            ') AS extollo_target_query'
        ].join('\n')
    }

    public renderRangedSelect(query: string, start: number, end: number): string {
        return [
            'SELECT *',
            'FROM (',
            ...query.split('\n').map(x => `  ${x}`),
            ') AS extollo_target_query',
            `OFFSET ${start} LIMIT ${(end - start) + 1}`
        ].join('\n')
    }

    /** Render the fields from the builder class to PostgreSQL syntax. */
    protected renderFields(builder: AbstractBuilder<any>) {
        return builder.appliedFields.map((field: SpecifiedField) => {
            let columnString: string
            if ( typeof field === 'string' ) columnString = field.split('.').map(x => `"${x}"`).join('.')
            else if ( field instanceof QuerySafeValue ) columnString = field.toString()
            else if ( typeof field.field === 'string' ) columnString = field.field.split('.').map(x => `"${x}"`).join('.')
            else columnString = field.field.toString()

            let aliasString = ''
            if ( typeof field !== 'string' && !(field instanceof QuerySafeValue) ) aliasString = ` AS "${field.alias}"`

            return `${columnString}${aliasString}`
        })
    }

    public renderSelect(builder: AbstractBuilder<any>): string {
        const indent = (item: string, level = 1) => Array(level + 1).fill('').join('  ') + item
        const queryLines = [
            `SELECT${builder.appliedDistinction ? ' DISTINCT' : ''}`
        ]

        // Add fields
        // FIXME error if no fields
        const fields = this.renderFields(builder).map(x => indent(x)).join(',\n')

        queryLines.push(fields)

        // Add table source
        // FIXME error if no source
        const source = builder.querySource
        if ( source ) {
            const tableString = typeof source === 'string' ? source : source.table
            const table: string = tableString.split('.').map(x => `"${x}"`).join('.')
            queryLines.push('FROM ' + (typeof source === 'string' ? table : `${table} "${source.alias}"`))
        }

        // Add constraints
        const wheres = this.renderConstraints(builder.appliedConstraints)
        if ( wheres.trim() ) {
            queryLines.push('WHERE')
            queryLines.push(wheres)
        }

        // Add group by
        if ( builder.appliedGroupings?.length ) {
            const grouping = builder.appliedGroupings.map(group => {
                return indent(group.split('.').map(x => `"${x}"`).join('.'))
            }).join(',\n')

            queryLines.push('GROUP BY')
            queryLines.push(grouping)
        }

        // Add order by
        if ( builder.appliedOrder?.length ) {
            const ordering = builder.appliedOrder.map(x => indent(`${x.field.split('.').map(x => '"' + x + '"').join('.')} ${x.direction}`)).join(',\n')
            queryLines.push('ORDER BY')
            queryLines.push(ordering)
        }

        // Add limit/offset
        const pagination = builder.appliedPagination
        if ( pagination.take ) {
            queryLines.push(`LIMIT ${pagination.take}${pagination.skip ? ' OFFSET ' + pagination.skip : ''}`)
        } else if ( pagination.skip ) {
            queryLines.push(`OFFSET ${pagination.skip}`)
        }

        return queryLines.join('\n')
    }

    // TODO support FROM, RETURNING
    public renderUpdate(builder: AbstractBuilder<any>, data: {[key: string]: EscapeValue}): string {
        const indent = (item: string, level = 1) => Array(level + 1).fill('').join('  ') + item
        const queryLines: string[] = []

        // Add table source
        const source = builder.querySource
        if ( source ) {
            const tableString = typeof source === 'string' ? source : source.table
            const table: string = tableString.split('.').map(x => `"${x}"`).join('.')
            queryLines.push('UPDATE ' + (typeof source === 'string' ? table : `${table} "${source.alias}"`))
        }

        queryLines.push(this.renderUpdateSet(data))

        // Add constraints
        const wheres = this.renderConstraints(builder.appliedConstraints)
        if ( wheres.trim() ) {
            queryLines.push('WHERE')
            queryLines.push(wheres)
        }

        return queryLines.join('\n')
    }

    public renderExistential(builder: AbstractBuilder<any>): string {
        const query = builder.clone()
            .clearFields()
            .field(raw('TRUE'))
            .limit(1)

        return this.renderSelect(query)
    }

    // FIXME: subquery support here and with select
    public renderInsert(builder: AbstractBuilder<any>, data: {[key: string]: EscapeValue}|{[key: string]: EscapeValue}[] = []): string {
        const indent = (item: string, level = 1) => Array(level + 1).fill('').join('  ') + item
        const queryLines: string[] = []

        if ( !Array.isArray(data) ) data = [data]
        const columns = Object.keys(data[0])

        // Add table source
        const source = builder.querySource
        if ( source ) {
            const tableString = typeof source === 'string' ? source : source.table
            const table: string = tableString.split('.').map(x => `"${x}"`).join('.')
            queryLines.push('INSERT INTO ' + (typeof source === 'string' ? table : `${table} AS "${source.alias}"`)
                + (columns.length ? ` (${columns.join(', ')})` : ''))
        }

        if ( Array.isArray(data) && !data.length ) {
            queryLines.push('DEFAULT VALUES')
        } else {
            queryLines.push('VALUES')

            const valueString = data.map(row => {
                    const values = columns.map(x => this.escape(row[x]))
                    return indent(`(${values.join(', ')})`)
                })
                .join(',\n')

            queryLines.push(valueString)
        }

        // Add return fields
        if ( builder.appliedFields?.length ) {
            queryLines.push('RETURNING')
            const fields = this.renderFields(builder).map(x => indent(x)).join(',\n')

            queryLines.push(fields)
        }

        return queryLines.join('\n')
    }

    public renderDelete(builder: AbstractBuilder<any>): string {
        const indent = (item: string, level = 1) => Array(level + 1).fill('').join('  ') + item
        const queryLines: string[] = []

        // Add table source
        const source = builder.querySource
        if ( source ) {
            const tableString = typeof source === 'string' ? source : source.table
            const table: string = tableString.split('.').map(x => `"${x}"`).join('.')
            queryLines.push('DELETE FROM ' + (typeof source === 'string' ? table : `${table} "${source.alias}"`))
        }

        // Add constraints
        const wheres = this.renderConstraints(builder.appliedConstraints)
        if ( wheres.trim() ) {
            queryLines.push('WHERE')
            queryLines.push(wheres)
        }

        // Add return fields
        if ( builder.appliedFields?.length ) {
            queryLines.push('RETURNING')

            const fields = this.renderFields(builder).map(x => indent(x)).join(',\n')

            queryLines.push(fields)
        }

        return queryLines.join('\n')
    }

    public renderConstraints(constraints: Constraint[]): string {
        const constraintsToSql = (constraints: Constraint[], level = 1): string => {
            const indent = Array(level * 2).fill(' ').join('')
            let statements = []

            for ( const constraint of constraints ) {
                if ( isConstraintGroup(constraint) ) {
                    statements.push(`${indent}${statements.length < 1 ? '' : constraint.preop + ' '}(\n${constraintsToSql(constraint.items, level + 1)}\n${indent})`)
                } else if ( isConstraintItem(constraint) ) {
                    const field: string = constraint.field.split('.').map(x => `"${x}"`).join('.')
                    statements.push(`${indent}${statements.length < 1 ? '' : constraint.preop + ' '}${field} ${constraint.operator} ${this.escape(constraint.operand).value}`)
                }
            }

            return statements.filter(Boolean).join('\n')
        }

        return constraintsToSql(constraints)
    }

    public renderUpdateSet(data: {[key: string]: EscapeValue}) {
        const sets = []
        for ( const key in data ) {
            if ( !data.hasOwnProperty(key) ) continue

            sets.push(`  "${key}" = ${this.escape(data[key])}`)
        }

        return ['SET', ...sets].join('\n')
    }
}